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Sodium perbromate is the chemical compound composed of the sodium ion and the perbromate ion, with the chemical formula NaBrO 4 .
Sodium perbromate can be prepared by reacting sodium bromate with fluorine and sodium hydroxide : [ 1 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NaBrO4 |
Sodium acetate , CH 3 COONa, also abbreviated Na O Ac , [ 8 ] is the sodium salt of acetic acid . This salt is colorless, deliquescent , and hygroscopic .
Sodium acetate is used as the carbon source for culturing bacteria . Sodium acetate can also be useful for increasing yields of DNA isolation by ethanol precipitation .
Sodium acetate is used in the textile industry to neutralize sulfuric acid waste streams and also as a photoresist while using aniline dyes . It is also a pickling agent in chrome tanning and helps to impede vulcanization of chloroprene in synthetic rubber production. It is also used to reduce static electricity during production of disposable cotton pads.
Sodium acetate is used to mitigate water damage to concrete by acting as a concrete sealant , while also being environmentally benign and cheaper than the commonly used epoxy alternative for sealing concrete against water permeation . [ 9 ]
Sodium acetate (anhydrous) is widely used as a shelf-life extending agent and pH-control agent. [ 10 ] It is safe to eat at low concentration. [ 11 ]
A solution of sodium acetate (a basic salt of acetic acid) and acetic acid can act as a buffer to keep a relatively constant pH level. This is useful especially in biochemical applications where reactions are pH-dependent in a mildly acidic range (pH 4–6).
Sodium acetate is also used in heating pads , hand warmers , and "hot ice". A supersaturated solution of sodium acetate in water is supplied with a device to initiate crystallization, a process that releases substantial heat.
Sodium acetate trihydrate crystals melt at 58–58.4 °C (136.4–137.1 °F), [ 12 ] [ 13 ] and the liquid sodium acetate dissolves in the released water of crystallization . When heated past the melting point and subsequently allowed to cool, the aqueous solution becomes supersaturated . This solution is capable of cooling to room temperature without forming crystals. By pressing on a metal disc within the heating pad, a nucleation center is formed, causing the solution to crystallize back into solid sodium acetate trihydrate. The process of crystallization is exothermic . [ 14 ] The latent heat of fusion is about 264–289 kJ/kg. [ 12 ] Unlike some types of heat packs, such as those dependent upon irreversible chemical reactions, a sodium acetate heat pack can be easily reused by immersing the pack in boiling water for a few minutes, until the crystals are completely dissolved, and allowing the pack to slowly cool to room temperature. [ 15 ]
Sodium acetate trihydrate can also be used as a phase-change material to store heat, especially to provide domestic hot water for heat pump applications. The heat store consists of a well-insulated container filled with the salt through which pass a pair of copper coils. One coil is used to melt the material by passing hot water from either solar thermal panels or a heat pump . Cold mains water passes through the other coil where its temperature is raised to 40 or 50 ˚C to provide water for washing or cleaning. This process can be cycled almost indefinitely. An example is the Sunamp Thermino. [ 16 ]
For laboratory use, sodium acetate is inexpensive and usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of acetic acid , commonly in the 5–18% solution known as vinegar , with sodium carbonate ("washing soda"), sodium bicarbonate ("baking soda"), or sodium hydroxide ("lye", or "caustic soda"). Any of these reactions produce sodium acetate and water or sodium acetate and carbonic acid. When a sodium and carbonate ion-containing compound is used as the reactant, the carbonate anion from sodium bicarbonate or carbonate, reacts with the hydrogen from the carboxyl group (-COOH) in acetic acid, forming carbonic acid . Carbonic acid readily decomposes under normal conditions into gaseous carbon dioxide and water. This is the reaction taking place in the well-known "volcano" that occurs when the household products, baking soda and vinegar, are combined.
Industrially, sodium acetate trihydrate is prepared by reacting acetic acid with sodium hydroxide using water as the solvent .
To manufacture anhydrous sodium acetate industrially, the Niacet Process is used. Sodium metal ingots are extruded through a die to form a ribbon of sodium metal, usually under an inert gas atmosphere such as N 2 then immersed in anhydrous acetic acid .
The hydrogen gas is normally a valuable byproduct.
The crystal structure of anhydrous sodium acetate has been described as alternating sodium-carboxylate and methyl group layers. [ 17 ] Sodium acetate trihydrate 's structure consists of distorted octahedral coordination at sodium. Adjacent octahedra share edges to form one-dimensional chains. Hydrogen bonding in two dimensions between acetate ions and water of hydration links the chains into a three-dimensional network. [ 18 ] [ 19 ]
Sodium acetate can be used to form an ester with an alkyl halide such as bromoethane :
Sodium acetate undergoes decarboxylation to form methane (CH 4 ) under forcing conditions (pyrolysis in the presence of sodium hydroxide):
Calcium oxide is the typical catalyst used for this reaction.
Cesium salts also catalyze this reaction. [ citation needed ] | https://en.wikipedia.org/wiki/NaC2H3O2 |
Sodium ethoxide, also referred to as sodium ethanolate , is the ionic , organic compound with the formula CH 3 CH 2 ONa , C 2 H 5 O Na , or NaOEt (Et = ethyl ). It is a white solid, although impure samples appear yellow or brown. It dissolves in polar solvents such as ethanol . It is commonly used as a strong base . [ 2 ]
Few procedures have been reported to prepare the anhydrous solid. Instead the material is typically prepared in a solution with ethanol. It is commercially available and as a solution in ethanol. It is easily prepared in the laboratory by treating sodium metal with absolute ethanol : [ 3 ]
The reaction of sodium hydroxide with anhydrous ethanol suffers from incomplete conversion to the ethoxide, but can still produce dry NaOEt by precipitation using acetone, [ 4 ] or by drying using additional NaOH. [ 5 ]
The crystal structure of sodium ethoxide has been determined by X-ray crystallography . It consists of layers of alternating Na + and O − centres with disordered ethyl groups covering the top and bottom of each layer. The ethyl layers pack back-to-back resulting in a lamellar structure . The reaction of sodium and ethanol sometimes forms other products such as the disolvate CH 3 CH 2 ONa·2 CH 3 CH 2 OH . Its crystal structure has been determined, although the structure of other phases in the CH 3 CH 2 ONa/CH 3 CH 2 OH system remain unknown. [ 6 ]
Sodium ethoxide is commonly used as a base in the Claisen condensation [ 7 ] and malonic ester synthesis . [ 8 ] Sodium ethoxide may either deprotonate the α-position of an ester molecule, forming an enolate , or the ester molecule may undergo a nucleophilic substitution called transesterification . If the starting material is an ethyl ester, trans-esterification is irrelevant since the product is identical to the starting material. In practice, the alcohol/alkoxide solvating mixture must match the alkoxy components of the reacting esters to minimize the number of different products.
Many alkoxides are prepared by salt metathesis from sodium ethoxide.
Sodium ethoxide is prone to reaction with both water and carbon dioxide in the air . [ 9 ] This leads to degradation of stored samples over time, even in solid form. The physical appearance of degraded samples may not be obvious, but samples of sodium ethoxide gradually turn dark on storage. It has been reported that even newly-obtained commercial batches of sodium ethoxide show variable levels of degradation, and responsible as a major source of irreproducibility when used in Suzuki reactions . [ 9 ]
In moist air, CH 3 CH 2 ONa hydrolyses rapidly to sodium hydroxide (NaOH). The conversion is not obvious and typical samples of CH 3 CH 2 ONa are contaminated with NaOH.
In moisture -free air, solid sodium ethoxide can form sodium ethyl carbonate from fixation of carbon dioxide from the air. Further reactions lead to degradation into a variety of other sodium salts and diethyl ether . [ 9 ]
This instability can be prevented by storing sodium ethoxide under an inert atmosphere (e.g., N 2 ).
Sodium ethoxide is a strong base , and is therefore corrosive. | https://en.wikipedia.org/wiki/NaC2H5O |
Sodium benzoate also known as benzoate of soda is the sodium salt of benzoic acid , widely used as a food preservative (with an E number of E211 ) and a pickling agent . It appears as a white crystalline chemical with the formula C 6 H 5 COONa.
Sodium benzoate is commonly produced by the neutralization of sodium hydroxide (NaOH) with benzoic acid (C 6 H 5 COOH), [ 3 ] which is itself produced commercially by partial oxidation of toluene with oxygen .
Sodium benzoate can be decarboxylated with strong base and heat, yielding benzene : [ 4 ]
Sodium benzoate is not a naturally occurring substance. However many foods are natural sources of benzoic acid, its salts, and its esters . [ 5 ] Fruits and vegetables can be rich sources, particularly berries such as cranberry and bilberry . Other sources include seafood , such as prawns , and dairy products . [ citation needed ]
Sodium benzoate can act as a food preservative. It is most widely used in acidic foods such as salad dressings (for example acetic acid in vinegar ), carbonated drinks ( carbonic acid ), jams and fruit juices ( citric acid ), pickles ( acetic acid ), condiments , and frozen yogurt toppings. It is also used as a preservative in medicines and cosmetics. [ 6 ] [ 7 ] Under these conditions it is converted into benzoic acid (E210), which is bacteriostatic and fungistatic . Benzoic acid is generally not used directly due to its poor water solubility.
Concentration as a food preservative is limited by the FDA in the U.S. to 0.1% by weight. [ 8 ] Sodium benzoate is also allowed as an animal food additive at up to 0.1%, per the Association of American Feed Control Officials. [ 9 ] Sodium benzoate has been replaced by potassium sorbate in the majority of soft drinks in the United Kingdom . [ 10 ]
In the 19th century, sodium benzoate as a food ingredient was investigated by Harvey W. Wiley with his 'Poison Squad' as part of the US Department of Agriculture . This led to the 1906 Pure Food and Drug Act , a key event in the early history of food regulation in the United States .
Sodium benzoate is used as a treatment for urea cycle disorders due to its ability to bind amino acids. [ 11 ] [ 12 ] This leads to excretion of these amino acids and a decrease in ammonia levels. Recent research shows that sodium benzoate may be beneficial as an add-on therapy (1 gram/day) in schizophrenia . [ 13 ] [ 14 ] [ 15 ] Total Positive and Negative Syndrome Scale scores dropped by 21% compared to placebo.
Sodium benzoate, along with phenylbutyrate , is used to treat hyperammonemia . [ 16 ] [ 17 ]
Sodium benzoate, along with caffeine , is used to treat postdural puncture headache , respiratory depression associated with overdosage of narcotics , [ 18 ] [ 19 ] and with ergotamine to treat vascular headache . [ 20 ]
Sodium benzoate is also used in fireworks as a fuel in whistle mix , a powder that emits a whistling noise when compressed into a tube and ignited. [ 21 ] [ 22 ]
The mechanism starts with the absorption of benzoic acid into the cell. If the intracellular pH falls to 5 or lower, the anaerobic fermentation of glucose through phosphofructokinase decreases sharply, [ 23 ] which inhibits the growth and survival of microorganisms that cause food spoilage.
In the United States , sodium benzoate is designated as generally recognized as safe (GRAS) by the Food and Drug Administration . [ 24 ] The International Programme on Chemical Safety found no adverse effects in rats at doses of 647–825 mg/kg of body weight per day. [ 25 ] [ 26 ]
Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice. [ 27 ]
The human body rapidly clears sodium benzoate by combining it with glycine to form hippuric acid which is then excreted. [ 26 ] The metabolic pathway for this begins with the conversion of benzoate by butyrate-CoA ligase into an intermediate product, benzoyl-CoA , [ 28 ] which is then metabolized by glycine N -acyltransferase into hippuric acid. [ 29 ]
In combination with ascorbic acid (vitamin C, E300), sodium benzoate and potassium benzoate may form benzene . In 2006, the Food and Drug Administration tested 100 beverages available in the United States that contained both ascorbic acid and benzoate. Four had benzene levels that were above the 5 ppb Maximum Contaminant Level set by the Environmental Protection Agency for drinking water. [ 30 ] Most of the beverages that tested above the limit have been reformulated and subsequently tested below the safety limit. [ 30 ] Heat, light and shelf life can increase the rate at which benzene is formed. Hot peppers naturally contain vitamin C ("nearly as much as in one orange" [ 31 ] ) so the observation about beverages applies to pepper sauces containing sodium benzoate, like Texas Pete .
Research published, including in 2007 for the UK's Food Standards Agency (FSA) suggests that certain artificial colors , when paired with sodium benzoate, may be linked to hyperactive behavior and other ADHD symptoms. The results were inconsistent regarding sodium benzoate, so the FSA recommended further study. [ 32 ] [ 33 ] [ 34 ] The Food Standards Agency concluded that the observed increases in hyperactive behavior, if real, were more likely to be linked to the artificial colors than to sodium benzoate. [ 34 ] The report's author, Jim Stevenson from Southampton University , said: "The results suggest that consumption of certain mixtures of artificial food colours and sodium benzoate preservative are associated with increases in hyperactive behaviour in children. . . . Many other influences are at work but this at least is one a child can avoid." [ 34 ]
. | https://en.wikipedia.org/wiki/NaC6H5CO2 |
Sodium salicylate is a sodium salt of salicylic acid . It can be prepared from sodium phenolate and carbon dioxide under higher temperature and pressure. Historically, it has been synthesized by refluxing methyl salicylate ( wintergreen oil) with an excess of sodium hydroxide . [ 4 ]
Sodium salicylate is of the salicylate family. It is a shiny white powder with an aromatic taste. [ 5 ]
It is used in medicine as an analgesic and antipyretic . [ 6 ] Sodium salicylate also acts as non-steroidal anti-inflammatory drug (NSAID), and induces apoptosis in cancer cells [ 7 ] [ 8 ] [ 9 ] and also necrosis . [ 10 ] It is also a potential replacement for aspirin for people sensitive to it. It may also be used as a phosphor for the detection of vacuum ultraviolet radiation and beta radiation . [ 11 ] | https://en.wikipedia.org/wiki/NaC7H5O3 |
Sodium acetate , CH 3 COONa, also abbreviated Na O Ac , [ 8 ] is the sodium salt of acetic acid . This salt is colorless, deliquescent , and hygroscopic .
Sodium acetate is used as the carbon source for culturing bacteria . Sodium acetate can also be useful for increasing yields of DNA isolation by ethanol precipitation .
Sodium acetate is used in the textile industry to neutralize sulfuric acid waste streams and also as a photoresist while using aniline dyes . It is also a pickling agent in chrome tanning and helps to impede vulcanization of chloroprene in synthetic rubber production. It is also used to reduce static electricity during production of disposable cotton pads.
Sodium acetate is used to mitigate water damage to concrete by acting as a concrete sealant , while also being environmentally benign and cheaper than the commonly used epoxy alternative for sealing concrete against water permeation . [ 9 ]
Sodium acetate (anhydrous) is widely used as a shelf-life extending agent and pH-control agent. [ 10 ] It is safe to eat at low concentration. [ 11 ]
A solution of sodium acetate (a basic salt of acetic acid) and acetic acid can act as a buffer to keep a relatively constant pH level. This is useful especially in biochemical applications where reactions are pH-dependent in a mildly acidic range (pH 4–6).
Sodium acetate is also used in heating pads , hand warmers , and "hot ice". A supersaturated solution of sodium acetate in water is supplied with a device to initiate crystallization, a process that releases substantial heat.
Sodium acetate trihydrate crystals melt at 58–58.4 °C (136.4–137.1 °F), [ 12 ] [ 13 ] and the liquid sodium acetate dissolves in the released water of crystallization . When heated past the melting point and subsequently allowed to cool, the aqueous solution becomes supersaturated . This solution is capable of cooling to room temperature without forming crystals. By pressing on a metal disc within the heating pad, a nucleation center is formed, causing the solution to crystallize back into solid sodium acetate trihydrate. The process of crystallization is exothermic . [ 14 ] The latent heat of fusion is about 264–289 kJ/kg. [ 12 ] Unlike some types of heat packs, such as those dependent upon irreversible chemical reactions, a sodium acetate heat pack can be easily reused by immersing the pack in boiling water for a few minutes, until the crystals are completely dissolved, and allowing the pack to slowly cool to room temperature. [ 15 ]
Sodium acetate trihydrate can also be used as a phase-change material to store heat, especially to provide domestic hot water for heat pump applications. The heat store consists of a well-insulated container filled with the salt through which pass a pair of copper coils. One coil is used to melt the material by passing hot water from either solar thermal panels or a heat pump . Cold mains water passes through the other coil where its temperature is raised to 40 or 50 ˚C to provide water for washing or cleaning. This process can be cycled almost indefinitely. An example is the Sunamp Thermino. [ 16 ]
For laboratory use, sodium acetate is inexpensive and usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of acetic acid , commonly in the 5–18% solution known as vinegar , with sodium carbonate ("washing soda"), sodium bicarbonate ("baking soda"), or sodium hydroxide ("lye", or "caustic soda"). Any of these reactions produce sodium acetate and water or sodium acetate and carbonic acid. When a sodium and carbonate ion-containing compound is used as the reactant, the carbonate anion from sodium bicarbonate or carbonate, reacts with the hydrogen from the carboxyl group (-COOH) in acetic acid, forming carbonic acid . Carbonic acid readily decomposes under normal conditions into gaseous carbon dioxide and water. This is the reaction taking place in the well-known "volcano" that occurs when the household products, baking soda and vinegar, are combined.
Industrially, sodium acetate trihydrate is prepared by reacting acetic acid with sodium hydroxide using water as the solvent .
To manufacture anhydrous sodium acetate industrially, the Niacet Process is used. Sodium metal ingots are extruded through a die to form a ribbon of sodium metal, usually under an inert gas atmosphere such as N 2 then immersed in anhydrous acetic acid .
The hydrogen gas is normally a valuable byproduct.
The crystal structure of anhydrous sodium acetate has been described as alternating sodium-carboxylate and methyl group layers. [ 17 ] Sodium acetate trihydrate 's structure consists of distorted octahedral coordination at sodium. Adjacent octahedra share edges to form one-dimensional chains. Hydrogen bonding in two dimensions between acetate ions and water of hydration links the chains into a three-dimensional network. [ 18 ] [ 19 ]
Sodium acetate can be used to form an ester with an alkyl halide such as bromoethane :
Sodium acetate undergoes decarboxylation to form methane (CH 4 ) under forcing conditions (pyrolysis in the presence of sodium hydroxide):
Calcium oxide is the typical catalyst used for this reaction.
Cesium salts also catalyze this reaction. [ citation needed ] | https://en.wikipedia.org/wiki/NaCH3CO2 |
Sodium acetate , CH 3 COONa, also abbreviated Na O Ac , [ 8 ] is the sodium salt of acetic acid . This salt is colorless, deliquescent , and hygroscopic .
Sodium acetate is used as the carbon source for culturing bacteria . Sodium acetate can also be useful for increasing yields of DNA isolation by ethanol precipitation .
Sodium acetate is used in the textile industry to neutralize sulfuric acid waste streams and also as a photoresist while using aniline dyes . It is also a pickling agent in chrome tanning and helps to impede vulcanization of chloroprene in synthetic rubber production. It is also used to reduce static electricity during production of disposable cotton pads.
Sodium acetate is used to mitigate water damage to concrete by acting as a concrete sealant , while also being environmentally benign and cheaper than the commonly used epoxy alternative for sealing concrete against water permeation . [ 9 ]
Sodium acetate (anhydrous) is widely used as a shelf-life extending agent and pH-control agent. [ 10 ] It is safe to eat at low concentration. [ 11 ]
A solution of sodium acetate (a basic salt of acetic acid) and acetic acid can act as a buffer to keep a relatively constant pH level. This is useful especially in biochemical applications where reactions are pH-dependent in a mildly acidic range (pH 4–6).
Sodium acetate is also used in heating pads , hand warmers , and "hot ice". A supersaturated solution of sodium acetate in water is supplied with a device to initiate crystallization, a process that releases substantial heat.
Sodium acetate trihydrate crystals melt at 58–58.4 °C (136.4–137.1 °F), [ 12 ] [ 13 ] and the liquid sodium acetate dissolves in the released water of crystallization . When heated past the melting point and subsequently allowed to cool, the aqueous solution becomes supersaturated . This solution is capable of cooling to room temperature without forming crystals. By pressing on a metal disc within the heating pad, a nucleation center is formed, causing the solution to crystallize back into solid sodium acetate trihydrate. The process of crystallization is exothermic . [ 14 ] The latent heat of fusion is about 264–289 kJ/kg. [ 12 ] Unlike some types of heat packs, such as those dependent upon irreversible chemical reactions, a sodium acetate heat pack can be easily reused by immersing the pack in boiling water for a few minutes, until the crystals are completely dissolved, and allowing the pack to slowly cool to room temperature. [ 15 ]
Sodium acetate trihydrate can also be used as a phase-change material to store heat, especially to provide domestic hot water for heat pump applications. The heat store consists of a well-insulated container filled with the salt through which pass a pair of copper coils. One coil is used to melt the material by passing hot water from either solar thermal panels or a heat pump . Cold mains water passes through the other coil where its temperature is raised to 40 or 50 ˚C to provide water for washing or cleaning. This process can be cycled almost indefinitely. An example is the Sunamp Thermino. [ 16 ]
For laboratory use, sodium acetate is inexpensive and usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of acetic acid , commonly in the 5–18% solution known as vinegar , with sodium carbonate ("washing soda"), sodium bicarbonate ("baking soda"), or sodium hydroxide ("lye", or "caustic soda"). Any of these reactions produce sodium acetate and water or sodium acetate and carbonic acid. When a sodium and carbonate ion-containing compound is used as the reactant, the carbonate anion from sodium bicarbonate or carbonate, reacts with the hydrogen from the carboxyl group (-COOH) in acetic acid, forming carbonic acid . Carbonic acid readily decomposes under normal conditions into gaseous carbon dioxide and water. This is the reaction taking place in the well-known "volcano" that occurs when the household products, baking soda and vinegar, are combined.
Industrially, sodium acetate trihydrate is prepared by reacting acetic acid with sodium hydroxide using water as the solvent .
To manufacture anhydrous sodium acetate industrially, the Niacet Process is used. Sodium metal ingots are extruded through a die to form a ribbon of sodium metal, usually under an inert gas atmosphere such as N 2 then immersed in anhydrous acetic acid .
The hydrogen gas is normally a valuable byproduct.
The crystal structure of anhydrous sodium acetate has been described as alternating sodium-carboxylate and methyl group layers. [ 17 ] Sodium acetate trihydrate 's structure consists of distorted octahedral coordination at sodium. Adjacent octahedra share edges to form one-dimensional chains. Hydrogen bonding in two dimensions between acetate ions and water of hydration links the chains into a three-dimensional network. [ 18 ] [ 19 ]
Sodium acetate can be used to form an ester with an alkyl halide such as bromoethane :
Sodium acetate undergoes decarboxylation to form methane (CH 4 ) under forcing conditions (pyrolysis in the presence of sodium hydroxide):
Calcium oxide is the typical catalyst used for this reaction.
Cesium salts also catalyze this reaction. [ citation needed ] | https://en.wikipedia.org/wiki/NaCH3COO |
Sodium bicarbonate ( IUPAC name : sodium hydrogencarbonate [ 10 ] ), commonly known as baking soda or bicarbonate of soda (or simply “ bicarb ” especially in the UK) is a chemical compound with the formula NaHCO 3 . It is a salt composed of a sodium cation ( Na + ) and a bicarbonate anion ( HCO − 3 ). Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda ( sodium carbonate ). The natural mineral form is nahcolite , although it is more commonly found as a component of the mineral trona . [ 11 ]
As it has long been known and widely used, the salt has many different names such as baking soda, bread soda, cooking soda, brewing soda and bicarbonate of soda and can often be found near baking powder in stores. The term baking soda is more common in the United States, while bicarbonate of soda is more common in Australia, the United Kingdom, and New Zealand. [ 12 ] Abbreviated colloquial forms such as sodium bicarb , bicarb soda , bicarbonate , and bicarb are common. [ 13 ]
The prefix bi- in "bicarbonate" comes from an outdated naming system predating molecular knowledge. It is based on the observation that there is twice as much carbonate ( CO 2− 3 ) per sodium in sodium bicarbonate (NaHCO 3 ) as there is in sodium carbonate (Na 2 CO 3 ). [ 14 ] The modern chemical formulas of these compounds now express their precise chemical compositions which were unknown when the name bi-carbonate of potash was coined (see also: bicarbonate ).
In cooking, baking soda is primarily used in baking as a leavening agent . When it reacts with acid or is heated, carbon dioxide is released, which causes expansion of the batter and forms the characteristic texture and grain in cakes, quick breads , soda bread , and other baked and fried foods. When an acid is used, the acid–base reaction can be generically represented as follows: [ 15 ]
Acidic materials that induce this reaction include hydrogen phosphates , cream of tartar , lemon juice, yogurt , buttermilk , cocoa , and vinegar . Baking soda may be used together with sourdough , which is acidic, making a lighter product with a less acidic taste. [ 16 ] Since the reaction occurs slowly at room temperature, mixtures (cake batter, etc.) can be allowed to stand without rising until they are heated in the oven. [ citation needed ]
Heat can also by itself cause sodium bicarbonate to act as a raising agent in baking because of thermal decomposition , releasing carbon dioxide at temperatures above 80 °C (180 °F), as follows: [ 17 ]
When used this way on its own, without the presence of an acidic component (whether in the batter or by the use of a baking powder containing acid), only half the available CO 2 is released (one CO 2 molecule is formed for every two equivalents of NaHCO 3 ). Additionally, in the absence of acid, thermal decomposition of sodium bicarbonate also produces sodium carbonate , which is strongly alkaline and gives the baked product a bitter, soapy taste and a yellow color.
Baking powder , also sold for cooking, contains around 30% of bicarbonate, and various acidic ingredients that are activated by the addition of water, without the need for additional acids in the cooking medium. [ 18 ] [ 19 ] [ 20 ] Many forms of baking powder contain sodium bicarbonate combined with calcium acid phosphate , sodium aluminium phosphate , or cream of tartar . [ 21 ] Baking soda is alkaline; the acid used in baking powder avoids a metallic taste when the chemical change during baking creates sodium carbonate. [ 22 ]
It is often used in conjunction with other bottled water food additives to add taste. [ 23 ] Its European Union E number is E500. [ 24 ]
Sodium bicarbonate is one of the main components of the common "black snake" firework . The effect is caused by the thermal decomposition, which produces carbon dioxide gas to produce a long snake-like ash as a combustion product of the other main component, sucrose . [ 25 ] Sodium bicarbonate also delays combustion reactions through the release of carbon dioxide and water, both of which are flame retardants, when heated.
It has weak disinfectant properties [ 26 ] [ 27 ] and it may be an effective fungicide against some organisms. [ 28 ] As baking soda will absorb musty smells, it has become a reliable method for used booksellers when making books less malodorous. [ 29 ]
Sodium bicarbonate can be used to extinguish small grease or electrical fires by being thrown over the fire, as heating of sodium bicarbonate releases carbon dioxide. [ 30 ] However, it should not be applied to fires in deep fryers ; the sudden release of gas may cause the grease to splatter. [ 30 ] Sodium bicarbonate is used in BC dry chemical fire extinguishers as an alternative to the more corrosive monoammonium phosphate in ABC extinguishers. The alkaline nature of sodium bicarbonate makes it the only dry chemical agent, besides Purple-K , that was used in large-scale fire suppression systems installed in commercial kitchens. [ 31 ]
Sodium bicarbonate has several fire-extinguishing mechanisms that act simultaneously. It decomposes into water and carbon dioxide when heated, an endothermic reaction that deprives the fire of heat. In addition, it forms intermediates that can scavenge the free radicals which are responsible for the propagation of fire . [ 32 ] With grease fires specifically, it also has a mild saponification effect, producing a soapy foam that can help smother the fire. [ 31 ]
Sodium bicarbonate reacts spontaneously with acids, releasing CO 2 gas as a reaction product. It is commonly used to neutralize unwanted acid solutions or acid spills in chemical laboratories. [ 33 ] It is not appropriate to use sodium bicarbonate to neutralize base [ 34 ] even though it is amphoteric , reacting with both acids and bases. [ 35 ]
Sodium bicarbonate is taken as a sports supplement to improve muscular endurance. [ 36 ] Studies conducted mostly in males have shown that sodium bicarbonate is most effective in enhancing performance in short-term, high-intensity activities. [ 37 ]
Sodium bicarbonate can prevent the growth of fungi when applied on leaves, although it will not kill the fungus. Excessive amounts of sodium bicarbonate can cause discolouration of fruits (two percent solution) and chlorosis (one percent solution). [ 38 ] Sodium bicarbonate is also commonly used as a free choice dietary supplement in sheep to help prevent bloat.
Sodium bicarbonate mixed with water can be used as an antacid to treat acid indigestion and heartburn . [ 39 ] [ 40 ] Its reaction with stomach acid produces salt , water, and carbon dioxide :
A mixture of sodium bicarbonate and polyethylene glycol such as PegLyte, [ 41 ] dissolved in water and taken orally, is an effective gastrointestinal lavage preparation and laxative prior to gastrointestinal surgery, gastroscopy , etc. [ citation needed ]
Intravenous sodium bicarbonate in an aqueous solution is sometimes used for cases of acidosis , or when insufficient sodium or bicarbonate ions are in the blood. [ 42 ] In cases of respiratory acidosis, the infused bicarbonate ion drives the carbonic acid/bicarbonate buffer of plasma to the left, and thus raises the pH. For this reason, sodium bicarbonate is used in medically supervised cardiopulmonary resuscitation . Infusion of bicarbonate is indicated only when the blood pH is markedly low (< 7.1–7.0). [ 43 ]
HCO 3 − is used for treatment of hyperkalemia , as it will drive K + back into cells during periods of acidosis. [ 44 ] Since sodium bicarbonate can cause alkalosis , it is sometimes used to treat aspirin overdoses. Aspirin requires an acidic environment for proper absorption, and a basic environment will diminish aspirin absorption in cases of overdose. [ 45 ] Sodium bicarbonate has also been used in the treatment of tricyclic antidepressant overdose . [ 46 ] It can also be applied topically as a paste, with three parts baking soda to one part water, to relieve some kinds of insect bites and stings (as well as accompanying swelling). [ 47 ]
Some alternative practitioners, such as Tullio Simoncini , have promoted baking soda as a cancer cure, which the American Cancer Society has warned against due to both its unproven effectiveness and potential danger in use. [ 48 ] Edzard Ernst has called the promotion of sodium bicarbonate as a cancer cure "one of the more sickening alternative cancer scams I have seen for a long time". [ 49 ]
Sodium bicarbonate can be added to local anaesthetics , to speed up the onset of their effects and make their injection less painful. [ 50 ] It is also a component of Moffett's solution , used in nasal surgery. [ 51 ]
It has been proposed that acidic diets weaken bones. [ 52 ] One systematic meta-analysis of the research shows no such effect. [ 53 ] Another also finds that there is no evidence that alkaline diets improve bone health, but suggests that there "may be some value" to alkaline diets for other reasons. [ 54 ]
Antacid (such as baking soda) solutions have been prepared and used by protesters to alleviate the effects of exposure to tear gas during protests. [ failed verification ] [ 55 ]
Similarly to its use in baking, sodium bicarbonate is used together with a mild acid such as tartaric acid as the excipient in effervescent tablets: when such a tablet is dropped in a glass of water, the carbonate leaves the reaction medium as carbon dioxide gas (HCO 3 − + H + → H 2 O + CO 2 ↑ or, more precisely, HCO 3 − + H 3 O + → 2 H 2 O + CO 2 ↑). This makes the tablet disintegrate, leaving the medication suspended and/or dissolved in the water together with the resulting salt (in this example, sodium tartrate ). [ 56 ]
Sodium bicarbonate is also used as an ingredient in some mouthwashes. It has anticaries and abrasive properties. [ 57 ] It works as a mechanical cleanser on the teeth and gums, neutralizes the production of acid in the mouth, and also acts as an antiseptic to help prevent infections. [ 58 ] [ 59 ] Sodium bicarbonate in combination with other ingredients can be used to make a dry or wet deodorant . [ 60 ] [ 61 ] Sodium bicarbonate may be used as a buffering agent , combined with table salt, when creating a solution for nasal irrigation . [ 62 ]
It is used in eye hygiene to treat blepharitis . This is done by adding a teaspoon of sodium bicarbonate to cool water that was recently boiled followed by gentle scrubbing of the eyelash base with a cotton swab dipped in the solution. [ 63 ] [ 64 ]
Sodium bicarbonate is used as a cattle feed supplement, in particular as a buffering agent for the rumen . [ 65 ]
Sodium bicarbonate is used in a process to remove paint and corrosion called sodablasting . As a blasting medium, sodium bicarbonate is used to remove surface contamination from softer and less resilient substrates such as aluminium, copper, or timber that could be damaged by silica sand abrasive media. [ 66 ]
A manufacturer recommends a paste made from baking soda with minimal water as a gentle scouring powder. [ 30 ] Such a paste can be useful in removing surface rust because the rust forms a water-soluble compound when in a concentrated alkaline solution. [ 67 ] Cold water should be used since hot-water solutions can corrode steel. [ 68 ] Sodium bicarbonate attacks the thin protective oxide layer that forms on aluminium, making it unsuitable for cleaning this metal. [ 69 ] A solution in warm water will remove the tarnish from silver when the silver is in contact with a piece of aluminium foil . [ 69 ] [ 70 ] Baking soda is commonly added to washing machines as a replacement for water softener and to remove odors from clothes. When diluted with warm water, it is also almost as effective in removing heavy tea and coffee stains from cups as sodium hydroxide .
During the Manhattan Project to develop the nuclear bomb in the early 1940s, the chemical toxicity of uranium was an issue. Uranium oxides were found to stick very well to cotton cloth and did not wash out with soap or laundry detergent . However, the uranium would wash out with a 2% solution of sodium bicarbonate. Clothing can become contaminated with toxic dust of depleted uranium (DU), which is very dense, hence it is used for counterweights in a civilian context and in armour-piercing projectiles. DU is not removed by normal laundering; washing with about 6 ounces (170 g) of baking soda in 2 gallons (7.5 L) of water will help wash it out. [ 71 ]
It is often claimed that baking soda is an effective odor remover [ 72 ] [ better source needed ] and recommended that an open box be kept in the refrigerator to absorb odor. [ 73 ] This idea was promoted by the leading U.S. brand of baking soda, Arm & Hammer , in an advertising campaign starting in 1972. [ 74 ] Though this campaign is considered a classic of marketing, leading within a year to more than half of American refrigerators containing a box of baking soda, [ 75 ] [ 76 ] there is little evidence that it is effective in this application. [ 77 ] [ 78 ]
An educational science experiment known as the "Baking Soda and Vinegar Volcano" uses the acid-base reaction with vinegar acid to mimic a volcanic eruption. The rapid production of CO 2 causes the liquid to foam up and overflow its container. Other ingredients such as dish soap and food coloring can be added to enhance the visual effect. [ 79 ] If this reaction is performed inside of a closed vessel (such as a bottle) with no way for gas to escape, it can cause an explosion if the pressure is high enough.
Sodium bicarbonate is an amphoteric compound. [ 35 ] Aqueous solutions are mildly alkaline due to the formation of carbonic acid and hydroxide ion: [ 35 ]
Sodium bicarbonate can sometimes be used as a mild neutralization agent and a safer alternative to strong bases like sodium hydroxide . [ 80 ] Reaction of sodium bicarbonate and an acid produces a salt and carbonic acid, which readily decomposes to carbon dioxide and water: [ 80 ]
Sodium bicarbonate reacts with acetic acid (found in vinegar), producing sodium acetate , water, and carbon dioxide :
Sodium bicarbonate reacts with bases such as sodium hydroxide to form carbonates:
At temperatures from 80–100 °C (176–212 °F), sodium bicarbonate gradually decomposes into sodium carbonate , water, and carbon dioxide. The conversion is faster at 200 °C (392 °F): [ 81 ]
Most bicarbonates undergo this dehydration reaction . Further heating converts the carbonate into the oxide (above 850 °C/1,560 °F): [ 81 ]
The generation of carbon dioxide and water partially explain the fire-extinguishing properties of NaHCO 3 , [ 31 ] although other factors like heat absorption and radical scavenging are more significant. [ 32 ]
In nature, sodium bicarbonate occurs almost exclusively as either nahcolite or trona . Trona is more common, as nahcolite is more soluble in water and the chemical equilibrium between the two minerals favors trona. [ 11 ] Significant nahcolite deposits are in the United States, Botswana and Kenya, Uganda, Turkey, and Mexico. [ 82 ] The biggest trona deposits are in the Green River basin in Wyoming. [ 83 ]
Nahcolite is sometimes found as a component of oil shale . [ 84 ]
If kept cool ( room temperature ) and dry (an airtight container is recommended to keep out moist air), sodium bicarbonate can be kept without a significant amount of decomposition for at least two or three years. [ 85 ] [ 86 ] [ 87 ] [ 88 ]
The word natron has been in use in many languages throughout modern times (in the forms of anatron , natrum and natron ) and originated (like Spanish , French and English natron as well as ' sodium ') via Arabic naṭrūn (or anatrūn ; cf. the Lower Egyptian “Natrontal” Wadi El Natrun , where a mixture of sodium carbonate and sodium hydrogen carbonate for the dehydration of mummies was used [ 89 ] ) from Greek nítron (νίτρον) (Herodotus; Attic lítron (λίτρον) ), which can be traced back to ancient Egyptian ntr . The Greek nítron (soda, saltpeter) was also used in Latin (sal) nitrum and in German Salniter (the source of Nitrogen , Nitrat etc.). [ 90 ] [ 91 ] The word saleratus , from Latin sal æratus (meaning "aerated salt"), was widely used in the 19th century for both sodium bicarbonate and potassium bicarbonate . [ 92 ]
In 1791, French chemist Nicolas Leblanc produced sodium carbonate (also known as soda ash). Pharmacist Valentin Rose the Younger is credited with the discovery of sodium bicarbonate in 1801 in Berlin. In 1846, two American bakers, John Dwight and Austin Church , established the first factory in the United States to produce baking soda from sodium carbonate and carbon dioxide . [ 93 ]
Saleratus , potassium or sodium bicarbonate, is mentioned in the novel Captains Courageous by Rudyard Kipling as being used extensively in the 1800s in commercial fishing to prevent freshly caught fish from spoiling. [ 94 ]
In 1919, US Senator Lee Overman declared that bicarbonate of soda could cure the Spanish flu . In the midst of the debate on 26 January 1919, he interrupted the discussion to announce the discovery of a cure. "I want to say, for the benefit of those who are making this investigation," he reported, "that I was told by a judge of a superior court in the mountain country of North Carolina they have discovered a remedy for this disease." The purported cure implied a critique of modern science and an appreciation for the simple wisdom of simple people. "They say that common baking soda will cure the disease," he continued, "that they have cured it with it, that they have no deaths up there at all; they use common baking soda, which cures the disease." [ 95 ]
Sodium bicarbonate is produced industrially from sodium carbonate : [ 96 ]
It is produced on the scale of about 100,000 tonnes/year (as of 2001) [ dubious – discuss ] [ 97 ] with a worldwide production capacity of 2.4 million tonnes per year (as of 2002). [ 98 ] Commercial quantities of baking soda are also produced by a similar method: soda ash, mined in the form of the ore trona , is dissolved in water and treated with carbon dioxide. Sodium bicarbonate precipitates as a solid from this solution. [ citation needed ]
Regarding the Solvay process , sodium bicarbonate is an intermediate in the reaction of sodium chloride , ammonia , and carbon dioxide . The product however shows low purity (75pc). [ citation needed ]
Although of no practical value, NaHCO 3 may be obtained by the reaction of carbon dioxide with an aqueous solution of sodium hydroxide: [ citation needed ]
Naturally occurring deposits of nahcolite (NaHCO 3 ) are found in the Eocene -age (55.8–33.9 Mya) Green River Formation , Piceance Basin in Colorado . Nahcolite was deposited as beds during periods of high evaporation in the basin. It is commercially mined using common underground mining techniques such as bore, drum, and longwall mining in a fashion very similar to coal mining. [ citation needed ]
It is also produced by solution mining, pumping heated water through nahcolite beds and crystallizing the dissolved nahcolite through a cooling crystallization process.
Since nahcolite is sometimes found in shale , it can be produced as a co-product of shale oil extraction , where it is recovered by solution mining. [ 84 ]
Sodium bicarbonate, as "bicarbonate of soda", was a frequent source of punch lines for Groucho Marx in Marx Brothers movies. In Duck Soup , Marx plays the leader of a nation at war. In one scene, he receives a message from the battlefield that his general is reporting a gas attack, and Groucho tells his aide: "Tell him to take a teaspoonful of bicarbonate of soda and a half a glass of water." [ 99 ] In A Night at the Opera , Groucho's character addresses the opening night crowd at an opera by saying of the lead tenor: "Signor Lassparri comes from a very famous family. His mother was a well-known bass singer. His father was the first man to stuff spaghetti with bicarbonate of soda, thus causing and curing indigestion at the same time." [ 100 ]
In the Joseph L. Mankewicz classic All About Eve , the Max Fabian character ( Gregory Ratoff ) has an extended scene with Margo Channing ( Bette Davis ) in which, suffering from heartburn, he requests and then drinks bicarbonate of soda, eliciting a prominent burp. Channing promises to always keep a box of bicarb with Max's name on it. | https://en.wikipedia.org/wiki/NaCHO3 |
Sodium cyanoborohydride is a chemical compound with the formula Na [ B H 3 ( C N )] . It is a colourless salt used in organic synthesis for chemical reduction including that of imines and carbonyls . Sodium cyanoborohydride is a milder reductant than other conventional reducing agents . [ 2 ]
Sodium cyanoborohydride is a salt. The cationic sodium ion, [Na] + , interacts with the anionic cyanoborohydride ion, [BH3(CN)] − . The anionic component of the salt is tetrahedral at the boron atom.
The electron-withdrawing cyanide substituent draws electron density away from the negatively charged boron; thus, reducing the electrophilic capabilities of the anionic component. [ 2 ] This electronic phenomenon causes sodium cyanoborohydride to have more mild reducing qualities than other reducing agents. For example, Na[BH 3 (CN)] is less reducing than its counterpart sodium borohydride , containing [BH 4 ] − . [ 2 ]
Sodium cyanoborohydride is a mild reducing agent. It is generally used for the reduction of imines . These reactions occur <pH 7 because the iminium ions are the actual substrates. [ 3 ]
Reductive amination , sometimes called the Borch reaction , is the conversion of a carbonyl into an amine through an intermediate imine . [ 4 ] The carbonyl is first treated with ammonia to promote imine formation by nucleophilic attack. The imine is then reduced to an amine by sodium cyanoborohydride. This reaction works on both aldehydes and ketones. The carbonyl can be treated with ammonia , a primary amine , or a secondary amine to produce, respectively, 1°, 2°, and 3° amines. [ 5 ]
Aromatic ketones and aldehydes can be reductively deoxygenated using sodium cyanoborohydride. [ 6 ] This means that the carbonyl oxygen is being removed completely from the molecule. Deoxygenation using sodium cyanoborohydride is often done in the presence of trimethylsilyl chloride , or TMSCl. [ 6 ]
Sodium cyanoborohydride can be purchased from most chemical suppliers. It can be synthesized by combining sodium cyanide and borane tetrahydrofuran . [ 7 ]
Since sodium cyanoborohydride is a mild reducing agent, it gives good chemoselectivity for reaction with certain functional groups in the presence of others. For example, sodium cyanoborohydride is generally incapable of reducing amides , ethers , esters and lactones , nitriles , or epoxides . [ 8 ] Therefore, it can selectively reduce some functionalities in the presence of others.
Some examples of selective reduction include:
The selectivity of this reducing agent makes it an important tool in organic synthesis . It allows for specific modifications to be made to complex organic molecules.
Georg Wittig was the first to synthesize a cyanoborohydride by treating lithium borohydride with hydrogen cyanide in 1951. [ 8 ] The corresponding compound, sodium cyanoborohydride, was synthesized following a similar rationale by reacting sodium borohydride with hydrogen cyanide . [ 10 ] The synthesis was later refined to use sodium cyanide and borane in THF making the process safer. [ 10 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NaCNBH3 |
Sodium chloride / ˌ s oʊ d i ə m ˈ k l ɔːr aɪ d / , [ 8 ] commonly known as edible salt , is an ionic compound with the chemical formula NaCl , representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic , and occurs as the mineral halite . In its edible form, it is commonly used as a condiment and food preservative . Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses . Another major application of sodium chloride is deicing of roadways in sub-freezing weather.
In addition to the many familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing. [ 9 ]
Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production. [ 10 ]
It is the starting point for the chloralkali process , the industrial process to produce chlorine and sodium hydroxide , according to the chemical equation
This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from the sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include PVC thermoplastics production, disinfectants, and solvents.
Sodium hydroxide is extensively used in many different industries enabling production of paper, soap, aluminum, and more.
Sodium chloride is used in the Solvay process to produce sodium carbonate and calcium chloride . Sodium carbonate, in turn, is used to produce glass , sodium bicarbonate , and dyes , as well as a myriad of other chemicals. In the Mannheim process , sodium chloride is used for the production of sodium sulfate and hydrochloric acid .
Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt is an important component of drilling fluids in well drilling. [ 11 ] It is used to flocculate and increase the density of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum. [ 9 ] Salt is also used to increase the curing of concrete in cemented casings. [ 10 ]
In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, [ 12 ] to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to increase yield in dyebaths and make the colors look sharper. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes. [ 10 ]
For use in the pulp and paper industry , it is used to manufacture sodium chlorate , which is then reacted with sulfuric acid and a reducing agent such as methanol to manufacture chlorine dioxide , a bleaching chemical that is widely used to bleach wood pulp .
In tanning and leather treatment, salt is added to animal hides to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides. [ 10 ]
In rubber manufacture, salt is used to make buna , neoprene , and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified latex made from chlorinated butadiene . [ 10 ] [ 9 ]
Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load. [ 10 ]
Hard water contains calcium and magnesium ions that interfere with action of soap and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use ion-exchange resins to remove ions that cause the hardness. These resins are generated and regenerated using sodium chloride. [ 10 ] [ 9 ]
The second major application of salt is for deicing and anti-icing of roads, both in grit bins and spread by winter service vehicles . In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated solution of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For deicing, mixtures of brine and salt are used, sometimes with additional agents such as calcium chloride and/or magnesium chloride . The use of salt or brine becomes ineffective below −10 °C (14 °F).
Salt for deicing in the United Kingdom predominantly comes from a single mine in Winsford in Cheshire . Prior to distribution it is mixed with <100 ppm of sodium ferrocyanide as an anticaking agent , which enables rock salt to flow freely out of the gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on the road longer, the treatment did not have to be repeated several times, saving time and money. [ 10 ]
In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is −21.12 °C (−6.02 °F) for 23.31 wt% of salt. Freezing near this concentration is however so slow that the eutectic point of −22.4 °C (−8.3 °F) can be reached with about 25 wt% of salt. [ 13 ]
Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their osmoregulation ability. [ 14 ] The omnipresence of salt in coastal areas poses a problem in any coating application, because trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal salt concentrations on surfaces are dependent on the authority and application. The IMO regulation is mostly used and sets salt levels to a maximum of 50 mg/m 2 soluble salts measured as sodium chloride. These measurements are done by means of a Bresle test . Salinization (increasing salinity, aka freshwater salinization syndrome ) and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways. [ 15 ]
In highway de-icing, salt has been associated with corrosion of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. Surface runoff , vehicle spraying, and windblown salt also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage, the spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied. [ 10 ] A 2009 study found that approximately 70% of the road salt being applied in the Minneapolis-St Paul metro area is retained in the local watershed. [ 16 ]
Some agencies are substituting beer , molasses , and beet juice instead of road salt. [ 17 ] Airlines utilize more glycol and sugar rather than salt-based solutions for deicing. [ 18 ]
Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder, fermentation -control additive, texture-control agent, and color developer. The salt consumption in the food industry is subdivided, in descending order of consumption, into other food processing, meat packers, canning , baking, dairy, and grain mill products. Salt is added to promote color development in bacon, ham and other processed meat products. As a preservative, salt inhibits the growth of bacteria. Salt acts as a binder in sausages to form a binding gel made up of meat, fat, and moisture. Salt also acts as a flavor enhancer and as a tenderizer . [ 10 ]
It is used as a cheap and safe desiccant because of its hygroscopic properties, making salting an effective method of food preservation historically; the salt draws water out of bacteria through osmotic pressure , keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest. Many microorganisms cannot live in a salty environment: water is drawn out of their cells by osmosis . For this reason salt is used to preserve some foods, such as bacon, fish, or cabbage.
In many dairy industries, salt is added to cheese as a color-, fermentation-, and texture-control agent. The dairy subsector includes companies that manufacture creamery butter, condensed and evaporated milk, frozen desserts, ice cream, natural and processed cheese, and specialty dairy products. In canning, salt is primarily added as a flavor enhancer and preservative . It also is used as a carrier for other ingredients, dehydrating agent, enzyme inhibitor and tenderizer. In baking, salt is added to control the rate of fermentation in bread dough. It also is used to strengthen the gluten (the elastic protein-water complex in certain doughs) and as a flavor enhancer, such as a topping on baked goods. The food-processing category also contains grain mill products. These products consist of milling flour and rice and manufacturing cereal breakfast food and blended or prepared flour. Salt is also used a seasoning agent in products such as potato chips, pretzels , and cat and dog food. [ 10 ]
Sodium chloride is used in veterinary medicine as emesis -causing agent. It is given as warm saturated solution. Emesis can also be caused by pharyngeal placement of small amount of plain salt or salt crystals.
For watering plants to use sodium chloride ( NaCl ) as a fertilizer, moderate concentration is used to avoid potential toxicity: 1–3 grams (0.035–0.106 oz) per liter is generally safe and effective for most plants. [ 19 ] [ 20 ] [ 21 ]
Sodium chloride is used together with water as one of the primary solutions for intravenous therapy . Nasal spray often contains a saline solution.
Sodium chloride is also available as an oral tablet and is taken to treat low sodium levels. [ 22 ]
Sodium chloride is the principal extinguishing agent in dry-powder fire extinguishers that are used on combustible metal fires, for metals such as magnesium, zirconium, titanium, and lithium (Class D extinguishers). The salt forms an oxygen-excluding crust that smothers the fire. [ 23 ]
Since at least medieval times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of shampoo and toothpaste and is commonly used to deice driveways, parking lots, and walkways.
Sodium chloride crystals have a transmittance of at least 90% (through 1 mm) for infrared light having wavelengths in the range 0.2– 18 μm . [ 24 ] They were used in optical components such as windows and lenses, where few non-absorbing alternatives existed in that spectral range. While inexpensive, NaCl crystals are soft and hygroscopic – when exposed to the water in ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum-sealed areas, or short-term uses such as prototyping. Materials that are mechanically stronger and less sensitive to moisture, such as zinc selenide and chalcogenide glasses , more widely used than NaCl.
In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular octahedron . In the language of close-packing , the larger chloride ions (167 pm in size [ 25 ] ) are arranged in a cubic array whereas the smaller sodium ions (116 pm [ 25 ] ) fill all the cubic gaps (octahedral voids) between them. This same basic structure is found in many other compounds and is commonly known as the NaCl structure or rock salt crystal structure. It can be represented as a face-centered cubic (fcc) lattice with a two-atom basis or as two interpenetrating face centered cubic lattices. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the fcc unit cell edge.
Solid sodium chloride has a melting point of 801 °C and liquid sodium chloride boils at 1465 °C. Atomic-resolution real-time video imaging allows visualization of the initial stage of crystal nucleation of sodium chloride. [ 26 ]
The Thermal conductivity of sodium chloride as a function of temperature has a maximum of 2.03 W/(cm K) at 8 K (−265.15 °C; −445.27 °F) and decreases to 0.069 at 314 K (41 °C; 106 °F). It also decreases with doping . [ 27 ]
From cold (sub-freezing) solutions, salt crystallises with water of hydration as hydrohalite (the dihydrate NaCl·2 H 2 O ). [ 29 ]
In 2023, it was discovered that under pressure, sodium chloride can form the hydrates NaCl·8.5H 2 O and NaCl·13H 2 O. [ 30 ]
The attraction between the Na + and Cl − ions in the solid is so strong that only highly polar solvents like water dissolve NaCl well.
When dissolved in water, the sodium chloride framework disintegrates as the Na + and Cl − ions become surrounded by polar water molecules. These solutions consist of metal aquo complex with the formula [Na(H 2 O) 8 ] + , with the Na–O distance of 250 pm . The chloride ions are also strongly solvated, each being surrounded by an average of six molecules of water. [ 31 ] Solutions of sodium chloride have very different properties from pure water. The eutectic point is −21.12 °C (−6.02 °F) for 23.31% mass fraction of salt, and the boiling point of saturated salt solution is near 108.7 °C (227.7 °F). [ 13 ]
The pH of a sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl − ion, which is the conjugate base of the strong acid HCl . In other words, NaCl has no effect on system pH [ 32 ] in diluted solutions where the effects of ionic strength and activity coefficients are negligible.
Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different stoichiometries have been discovered; five new compounds were predicted (e.g., Na 3 Cl , Na 2 Cl , Na 3 Cl 2 , NaCl 3 , and NaCl 7 ). The existence of some of them has been experimentally confirmed at high pressures and other conditions: cubic and orthorhombic NaCl 3 , two-dimensional metallic tetragonal Na 3 Cl and exotic hexagonal NaCl. [ 34 ] This indicates that compounds violating chemical intuition are possible, in simple systems under non-ambient conditions. [ 35 ]
Salt is found in the Earth's crust as the mineral halite (rock salt), and a tiny amount exists as suspended sea salt particles in the atmosphere. [ 36 ] These particles are the dominant cloud condensation nuclei far out at sea, which allow the formation of clouds in otherwise non-polluted air . [ 37 ]
Salt is currently mass-produced by evaporation of seawater or brine from brine wells and salt lakes . Mining of rock salt is also a major source. China is the world's main supplier of salt. [ 10 ] In 2017, world production was estimated at 280 million tonnes , the top five producers (in million tonnes) being China (68.0), United States (43.0), India (26.0), Germany (13.0), and Canada (13.0). [ 38 ] Salt is also a byproduct of potassium mining. | https://en.wikipedia.org/wiki/NaCl |
Sodium hypochlorite is an alkaline inorganic chemical compound with the formula Na O Cl (also written as NaClO). It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. [ 4 ] It is the sodium salt of hypochlorous acid , consisting of sodium cations ( Na + ) and hypochlorite anions ( − OCl , also written as OCl − and ClO − ).
The anhydrous compound is unstable and may decompose explosively. [ 5 ] [ 6 ] It can be crystallized as a pentahydrate NaOCl·5H 2 O , a pale greenish-yellow solid which is not explosive and is stable if kept refrigerated. [ 7 ] [ 8 ] [ 9 ]
Sodium hypochlorite is most often encountered as a pale greenish-yellow dilute solution referred to as chlorine bleach, which is a household chemical widely used (since the 18th century) as a disinfectant and bleaching agent . In solution, the compound is unstable and easily decomposes, liberating chlorine , which is the active principle of such products. Sodium hypochlorite is still the most important chlorine-based bleach . [ 10 ] [ 11 ]
Its corrosive properties, common availability, and reaction products make it a significant safety risk. In particular, mixing liquid bleach with other cleaning products, such as acids found in limescale -removing products, will release toxic chlorine gas . A common misconception is that mixing bleach with ammonia also releases chlorine, but in reality they react to produce chloramines such as nitrogen trichloride . With excess ammonia and sodium hydroxide , hydrazine may be generated.
Anhydrous sodium hypochlorite can be prepared but, like many hypochlorites, it is highly unstable and decomposes explosively on heating or friction. [ 5 ] The decomposition is accelerated by carbon dioxide at Earth's atmospheric levels - around 4 parts per ten thousand. [ 6 ] [ 12 ] It is a white solid with the orthorhombic crystal structure . [ 13 ]
Sodium hypochlorite can also be obtained as a crystalline pentahydrate NaOCl·5H 2 O , which is not explosive and is much more stable than the anhydrous compound. [ 6 ] [ 7 ] The formula is sometimes given in its hydrous crystalline form as 2NaOCl·10H 2 O . [ 14 ] The Cl–O bond length in the pentahydrate is 1.686 Å. [ 9 ] The transparent, light greenish-yellow, orthorhombic [ 15 ] [ 16 ] crystals contain 44% NaOCl by weight and melt at 25–27 °C. The compound decomposes rapidly at room temperature, so it must be kept under refrigeration. At lower temperatures, however, it is quite stable: reportedly only 1% decomposition after 360 days at 7 °C. [ 8 ] [ 17 ]
A 1966 US patent claims that stable solid sodium hypochlorite dihydrate NaOCl·2H 2 O can be obtained by carefully excluding chloride ions ( Cl − ), which are present in the output of common manufacturing processes and are said to catalyze the decomposition of hypochlorite into chlorate ( ClO − 3 ) and chloride. In one test, the dihydrate was claimed to show only 6% decomposition after 13.5 months of storage at −25 °C. The patent also claims that the dihydrate can be reduced to the anhydrous form by vacuum drying at about 50 °C, yielding a solid that showed no decomposition after 64 hours at −25 °C. [ 18 ]
At typical ambient temperatures, sodium hypochlorite is more stable in dilute solutions that contain solvated Na + and OCl − ions. The density of the solution is 1.093 g/mL at 5% concentration, [ 19 ] and 1.21 g/mL at 14%, 20 °C. [ 20 ] Stoichiometric solutions are fairly alkaline , with pH 11 or higher [ 8 ] since the hypochlorite ion is a weak base :
The following species and equilibria are present in NaOCl/NaCl solutions: [ 21 ]
The second equilibrium equation above will be shifted to the right if the chlorine Cl 2 is allowed to escape as gas. The ratios of Cl 2 , HOCl, and OCl − in solution are also pH dependent. At pH below 2, the majority of the chlorine in the solution is in the form of dissolved elemental Cl 2 . At pH greater than 7.4, the majority is in the form of hypochlorite ClO − . [ 10 ] The equilibrium can be shifted by adding acids (such as hydrochloric acid ) or bases (such as sodium hydroxide ) to the solution:
At a pH of about 4, such as obtained by the addition of strong acids like hydrochloric acid , the amount of undissociated (nonionized) HOCl is highest. The reaction can be written as:
Sodium hypochlorite solutions combined with acid evolve chlorine gas, particularly strongly at pH < 2, by the reactions:
At pH > 8, the chlorine is practically all in the form of hypochlorite anions ( OCl − ). The solutions are fairly stable at pH 11–12. Even so, one report claims that a conventional 13.6% NaOCl reagent solution lost 17% of its strength after being stored for 360 days at 7 °C. [ 8 ] For this reason, in some applications one may use more stable chlorine-releasing compounds, such as calcium hypochlorite Ca(ClO) 2 or trichloroisocyanuric acid (CNClO) 3 . [ citation needed ]
Anhydrous sodium hypochlorite is soluble in methanol , and solutions are stable. [ citation needed ]
In solution, under certain conditions, the hypochlorite anion may also disproportionate ( autoxidize ) to chloride and chlorate : [ 22 ]
In particular, this reaction occurs in sodium hypochlorite solutions at high temperatures, forming sodium chlorate and sodium chloride: [ 22 ] [ 23 ]
This reaction is exploited in the industrial production of sodium chlorate.
An alternative decomposition of hypochlorite produces oxygen instead:
In hot sodium hypochlorite solutions, this reaction competes with chlorate formation, yielding sodium chloride and oxygen gas: [ 22 ]
These two decomposition reactions of NaOCl solutions are maximized at pH around 6. For example, at 80 °C, with NaOCl and NaCl concentrations of 80 mM , over the pH range 5−10.5, both reactions have rate proportional to [ HOCl ] 2 [ OCl − ] {\displaystyle [{\ce {HOCl}}]^{2}[{\ce {OCl-}}]} , decomposition is fastest at pH 6.5, and chlorate is produced with ~95% efficiency. [ 22 ] Above pH 11, both reactions have rate proportional to [ OCl − ] 2 {\displaystyle [{\ce {OCl-}}]^{2}} , decomposition is much slower, and chlorate is produced with ~90% efficiency. [ 24 ] This decomposition is affected by light [ 23 ] and metal ion catalysts such as copper , nickel , cobalt , [ 22 ] and iridium . [ 25 ] Catalysts like sodium dichromate Na 2 Cr 2 O 7 and sodium molybdate Na 2 MoO 4 may be added industrially to reduce the oxygen pathway, but a report claims that only the latter is effective. [ 22 ] [ failed verification ]
Titration of hypochlorite solutions is often done by adding a measured sample to an excess amount of acidified solution of potassium iodide (KI) and then titrating the liberated iodine ( I 2 ) with a standard solution of sodium thiosulfate or phenylarsine oxide , using starch as indicator, until the blue color disappears. [ 16 ]
According to one US patent, the stability of sodium hypochlorite content of solids or solutions can be determined by monitoring the infrared absorption due to the O–Cl bond. The characteristic wavelength is given as 140.25 μm for water solutions, 140.05 μm for the solid dihydrate NaOCl·2H 2 O , and 139.08 μm for the anhydrous mixed salt Na 2 (OCl)(OH) . [ 18 ]
Oxidation of starch by sodium hypochlorite, which adds carbonyl and carboxyl groups, is relevant to the production of modified starch products. [ 26 ]
In the presence of a phase-transfer catalyst , alcohols are oxidized to the corresponding carbonyl compound ( aldehyde or ketone ). [ 27 ] [ 8 ] Sodium hypochlorite can also oxidize organic sulfides to sulfoxides or sulfones ; disulfides or thiols to sulfonyl halides ; and imines to oxaziridines . [ 8 ] It can also de-aromatize phenols . [ 8 ]
Heterogeneous reactions of sodium hypochlorite and metals such as zinc proceed slowly to give the metal oxide or hydroxide: [ citation needed ]
Homogeneous reactions with metal coordination complexes proceed somewhat faster. This has been exploited in the Jacobsen epoxidation . [ citation needed ]
If not properly stored in airtight containers, sodium hypochlorite reacts with carbon dioxide to form sodium carbonate :
Sodium hypochlorite reacts with most nitrogen compounds to form volatile monochloramine , dichloramines , and nitrogen trichloride :
Sodium thiosulfate is an effective chlorine neutralizer. Rinsing with a 5 mg/L solution, followed by washing with soap and water, will remove chlorine odor from the hands. [ 28 ]
Potassium hypochlorite was first produced in 1789 by Claude Louis Berthollet in his laboratory on the Quai de Javel in Paris , France, by passing chlorine gas through a solution of potash lye . The resulting liquid, known as " Eau de Javel " ("Javel water"), was a weak solution of potassium hypochlorite. Antoine Labarraque replaced potash lye by the cheaper soda lye , thus obtaining sodium hypochlorite ( Eau de Labarraque ). [ 29 ] [ 30 ]
Hence, chlorine is simultaneously reduced and oxidized ; this process is known as disproportionation . [ citation needed ]
The process is also used to prepare the pentahydrate NaOCl·5H 2 O for industrial and laboratory use. In a typical process, chlorine gas is added to a 45–48% NaOH solution. Some of the sodium chloride precipitates and is removed by filtration, and the pentahydrate is then obtained by cooling the filtrate to 12 °C. [ 8 ]
Another method involved the reaction of sodium carbonate ("washing soda") with chlorinated lime ("bleaching powder"), a mixture of calcium hypochlorite Ca(OCl) 2 , calcium chloride CaCl 2 , and calcium hydroxide Ca(OH) 2 :
This method was commonly used to produce hypochlorite solutions for use as a hospital antiseptic that was sold after World War I under the names "Eusol", an abbreviation for Edinburgh University Solution Of (chlorinated) Lime – a reference to the university's pathology department, where it was developed. [ 31 ]
Near the end of the nineteenth century, E. S. Smith patented the chloralkali process : a method of producing sodium hypochlorite involving the electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite. [ 32 ] [ 30 ] [ 33 ] The key reactions are:
Both electric power and brine solutions were in cheap supply at the time, and various enterprising marketers took advantage of the situation to satisfy the market's demand for sodium hypochlorite. Bottled solutions of sodium hypochlorite were sold under numerous trade names. [ citation needed ]
Today, an improved version of this method, known as the Hooker process (named after Hooker Chemicals, acquired by Occidental Petroleum ), is the only large-scale industrial method of sodium hypochlorite production. In the process, sodium hypochlorite (NaClO) and sodium chloride (NaCl) are formed when chlorine is passed into a cold dilute sodium hydroxide solution. The chlorine is prepared industrially by electrolysis with minimal separation between the anode and the cathode . The solution must be kept below 40 °C (by cooling coils) to prevent the undesired formation of sodium chlorate . [ citation needed ]
Commercial solutions always contain significant amounts of sodium chloride (common salt) as the main by-product , as seen in the equation above.
A 1966 patent describes the production of solid stable dihydrate NaOCl·2H 2 O by reacting a chloride-free solution of hypochlorous acid HClO (such as prepared from chlorine monoxide ClO and water), with a concentrated solution of sodium hydroxide. In a typical preparation, 255 mL of a solution with 118 g/L HClO is slowly added with stirring to a solution of 40 g of NaOH in water 0 °C. Some sodium chloride precipitates and is removed by filtration. The solution is vacuum evaporated at 40–50 °C and 1–2 mmHg until the dihydrate crystallizes out. The crystals are vacuum-dried to produce a free-flowing crystalline powder. [ 18 ]
The same principle was used in a 1993 patent to produce concentrated slurries of the pentahydrate NaClO·5H 2 O . Typically, a 35% solution (by weight) of HClO is combined with sodium hydroxide at about or below 25 °C. The resulting slurry contains about 35% NaClO, and are relatively stable due to the low concentration of chloride. [ 34 ]
Household bleach sold for use in laundering clothes is a 3–8 % solution of sodium hypochlorite at the time of manufacture. Strength varies from one formulation to another and gradually decreases with long storage. Sodium hydroxide is usually added in small amounts to household bleach to slow down the decomposition of NaClO. [ 10 ]
Domestic use patio blackspot remover products are ~10% solutions of sodium hypochlorite.
A 10–25% solution of sodium hypochlorite is, according to Univar's safety sheet, supplied with synonyms or trade names bleach, Hypo, Everchlor, Chloros, Hispec, Bridos, Bleacol, or Vo-redox 9110. [ 35 ]
A 12% solution is widely used in waterworks for the chlorination of water , and a 15% solution is more commonly [ 36 ] used for disinfection of wastewater in treatment plants. Sodium hypochlorite can also be used for point-of-use disinfection of drinking water, [ 37 ] taking 0.2–2 mg of sodium hypochlorite per liter of water. [ 38 ]
Dilute solutions (50 ppm to 1.5%) are found in disinfecting sprays and wipes used on hard surfaces. [ 39 ] [ 40 ]
Household bleach is, in general, a solution containing 3–8% sodium hypochlorite, by weight, and 0.01–0.05% sodium hydroxide ; the sodium hydroxide is used to slow the decomposition of sodium hypochlorite into sodium chloride and sodium chlorate . [ 41 ]
Sodium hypochlorite has destaining properties. [ 42 ] Among other applications, it can be used to remove mold stains, dental stains caused by fluorosis , [ 43 ] and stains on crockery, especially those caused by the tannins in tea . It has also been used in laundry detergents and as a surface cleaner. It is also used in sodium hypochlorite washes .
Its bleaching, cleaning, deodorizing, and caustic effects are due to oxidation and hydrolysis ( saponification ). Organic dirt exposed to hypochlorite becomes water-soluble and non-volatile, which reduces its odor and facilitates its removal.
Sodium hypochlorite in solution exhibits broad-spectrum anti-microbial activity and is widely used in healthcare facilities in a variety of settings. [ 44 ] It is usually diluted in water depending on its intended use. "Strong chlorine solution" is a 0.5% solution of hypochlorite (containing approximately 5000 ppm free chlorine) used for disinfecting areas contaminated with body fluids, including large blood spills (the area is first cleaned with detergent before being disinfected). [ 44 ] [ 45 ] It may be made by diluting household bleach as appropriate (normally 1 part bleach to 9 parts water). [ 46 ] Such solutions have been demonstrated to inactivate both C. difficile [ 44 ] and HPV . [ 47 ] "Weak chlorine solution" is a 0.05% solution of hypochlorite used for washing hands, but is normally prepared with calcium hypochlorite granules. [ 45 ]
" Dakin's Solution " is a disinfectant solution containing a low concentration of sodium hypochlorite and some boric acid or sodium bicarbonate to stabilize the pH. It is effective with NaOCl concentrations as low as 0.025%. [ 48 ]
US government regulations allow food processing equipment and food contact surfaces to be sanitized with solutions containing bleach, provided that the solution is allowed to drain adequately before contact with food and that the solutions do not exceed 200 parts per million (ppm) available chlorine (for example, one tablespoon of typical household bleach containing 5.25% sodium hypochlorite, per gallon of water). [ 49 ] If higher concentrations are used, the surface must be rinsed with potable water after sanitizing.
A similar concentration of bleach in warm water is used to sanitize surfaces before brewing beer or wine. Surfaces must be rinsed with sterilized (boiled) water to avoid imparting flavors to the brew; the chlorinated byproducts of sanitizing surfaces are also harmful. The mode of disinfectant action of sodium hypochlorite is similar to that of hypochlorous acid.
Solutions containing more than 500 ppm available chlorine are corrosive to some metals , alloys , and many thermoplastics (such as acetal resin ) and need to be thoroughly removed afterward, so the bleach disinfection is sometimes followed by an ethanol disinfection. Liquids containing sodium hypochlorite as the main active component are also used for household cleaning and disinfection, for example toilet cleaners . [ 50 ] Some cleaners are formulated to be viscous so as not to drain quickly from vertical surfaces, such as the inside of a toilet bowl.
The undissociated (nonionized) hypochlorous acid is believed to react with and inactivate bacterial and viral enzymes.
Neutrophils of the human immune system produce small amounts of hypochlorite inside phagosomes , which digest bacteria and viruses.
Sodium hypochlorite has deodorizing properties, which go hand-in-hand with its cleaning properties. [ 42 ]
Sodium hypochlorite solutions have been used to treat dilute cyanide wastewater, such as electroplating wastes. In batch treatment operations, sodium hypochlorite has been used to treat more concentrated cyanide wastes, such as silver cyanide plating solutions. Toxic cyanide is oxidized to cyanate OCN − ) that is not toxic, idealized as follows:
Sodium hypochlorite is commonly used as a biocide in industrial applications to control slime and bacteria formation in water systems used at power plants, pulp and paper mills, etc., in solutions typically of 10–15% by weight.
Sodium hypochlorite is the medicament of choice due to its efficacy against pathogenic organisms and pulp digestion in endodontic therapy . Its concentration for use varies from 0.5% to 5.25%. At low concentrations it dissolves mainly necrotic tissue; at higher concentrations, it also dissolves vital tissue and additional bacterial species. One study has shown that Enterococcus faecalis was still present in the dentin after 40 minutes of exposure of 1.3% and 2.5% sodium hypochlorite, whereas 40 minutes at a concentration of 5.25% was effective in E. faecalis removal. [ 51 ] In addition to higher concentrations of sodium hypochlorite, longer time exposure and warming the solution (60 °C) also increases its effectiveness in removing soft tissue and bacteria within the root canal chamber. [ 51 ] 2% is a common concentration as there is less risk of an iatrogenic hypochlorite incident. [ 52 ] A hypochlorite incident is an immediate reaction of severe pain, followed by edema , haematoma , and ecchymosis as a consequence of the solution escaping the confines of the tooth and entering the periapical space. This may be caused by binding or excessive pressure on the irrigant syringe, or it may occur if the tooth has an unusually large apical foramen . [ 53 ]
At the various nerve agent (chemical warfare nerve gas) destruction facilities throughout the United States , 0.5-2.5% sodium hypochlorite is used to remove all traces of nerve agent or blister agent from Personal Protection Equipment after an entry is made by personnel into toxic areas. [ 54 ]
0.5-2.5% sodium hypochlorite is also used to neutralize any accidental releases of the nerve agent in the toxic areas. [ 55 ]
Lesser concentrations of sodium hypochlorite are used similarly in the Pollution Abatement System to ensure that no nerve agent is released into the furnace flue gas.
Dilute bleach baths have been used for decades to treat moderate to severe eczema in humans,. [ 56 ] [ 57 ] Still, it has not been clear why they work. One of the reasons why bleach helps is that eczema can frequently result in secondary infections, especially from bacteria like Staphylococcus aureus , which makes managing it difficult. Staphylococcus aureus infection is related to the pathogenesis of eczema and AD. Bleach baths are one method for lowering the risk of staph infections in people with eczema. The antibacterial and anti-inflammatory properties of sodium hypochlorite contribute to the reduction of harmful bacteria on the skin and the reduction of inflammation, respectively. [ 58 ] According to work published by researchers at the Stanford University School of Medicine in November 2013, a very dilute (0.005%) solution of sodium hypochlorite in water was successful in treating skin damage with an inflammatory component caused by radiation therapy , excess sun exposure or aging in laboratory mice . Mice with radiation dermatitis given daily 30-minute baths in bleach solution experienced less severe skin damage and better healing and hair regrowth than animals bathed in water. A molecule called nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is known to play a critical role in inflammation, aging, and response to radiation. The researchers found that if NF-κB activity was blocked in elderly mice by bathing them in bleach solution, the animals' skin began to look younger, going from old and fragile to thicker, with increased cell proliferation . The effect diminished after the baths were stopped, indicating that regular exposure was necessary to maintain skin thickness. [ 56 ] [ 59 ]
Dilute sodium hypochlorite solutions (as in household bleach) are irritating to mainly the skin and respiratory tract. Short-term skin contact with household bleach may cause dryness of the skin.
It is estimated that there are about 3,300 accidents needing hospital treatment caused by sodium hypochlorite solutions each year in British homes (RoSPA, 2002).
Sodium hypochlorite is a strong oxidizer . Oxidation reactions are corrosive . Solutions burn the skin and cause eye damage, especially when used in concentrated forms. As recognized by the NFPA, however, only solutions containing more than 40% sodium hypochlorite by weight are considered hazardous oxidizers. Solutions less than 40% are classified as a moderate oxidizing hazard (NFPA 430, 2000).
Household bleach and pool chlorinator solutions are typically stabilized by a significant concentration of lye (caustic soda, NaOH) as part of the manufacturing reaction. This additive will by itself cause caustic irritation or burns due to defatting and saponification of skin oils and destruction of tissue. The slippery feel of bleach on the skin is due to this process.
Contact of sodium hypochlorite solutions with metals may evolve flammable hydrogen gas. Containers may explode when heated due to the release of chlorine gas. [ 12 ]
Hypochlorite solutions are corrosive to common container materials such as stainless steel [ 8 ] and aluminium . The few compatible metals include titanium (which however is not compatible with dry chlorine) and tantalum . [ 10 ] Glass containers are safe. [ 8 ] Some plastics and rubbers are affected too; safe choices include polyethylene (PE), high density polyethylene (HDPE, PE-HD), polypropylene (PP), [ 8 ] some chlorinated and fluorinated polymers such as polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF); as well as ethylene propylene rubber , and Viton . [ 10 ]
Containers must allow the venting of oxygen produced by decomposition over time, otherwise, they may burst. [ 5 ]
Mixing bleach with some household cleaners can be hazardous.
Sodium hypochlorite solutions, such as liquid bleach, will release toxic chlorine gas when mixed with an acid , such as hydrochloric acid or vinegar .
A 2008 study indicated that sodium hypochlorite and organic chemicals (e.g., surfactants, fragrances) contained in several household cleaning products can react to generate chlorinated organic compounds. [ 60 ] The study showed that indoor air concentrations significantly increase (8–52 times for chloroform and 1–1170 times for carbon tetrachloride, respectively, above baseline quantities in the household) during the use of bleach containing products.
In particular, mixing hypochlorite bleaches with amines (for example, cleaning products that contain or release ammonia , ammonium salts, urea , or related compounds and biological materials such as urine ) produces chloramines. [ 61 ] [ 12 ] These gaseous products can cause acute lung injury. Chronic exposure, for example, from the air at swimming pools where chlorine is used as the disinfectant, can lead to the development of atopic asthma. [ 62 ]
Bleach can react violently with hydrogen peroxide and produce oxygen gas:
Explosive reactions or byproducts can also occur in industrial and laboratory settings when sodium hypochlorite is mixed with diverse organic compounds. [ 12 ]
The UK's National Institute for Health and Care Excellence in October 2008 recommended that Dakin's solution should not be used in routine wound care. [ 63 ]
In spite of its strong biocidal action, sodium hypochlorite per se has limited environmental impact, since the hypochlorite ion rapidly degrades before it can be absorbed by living beings. [ 64 ]
However, one major concern arising from sodium hypochlorite use is that it tends to form persistent chlorinated organic compounds , including known carcinogens , that can be absorbed by organisms and enter the food chain . These compounds may be formed during household storage and use as well as during industrial use. [ 41 ] For example, when household bleach and wastewater were mixed, 1–2% of the available chlorine was observed to form organic compounds. [ 41 ] As of 1994, not all the byproducts had been identified, but identified compounds include chloroform and carbon tetrachloride . [ 41 ] [ needs update ] The exposure to these chemicals from use is estimated to be within occupational exposure limits. [ 41 ] | https://en.wikipedia.org/wiki/NaClO |
Sodium chlorate is an inorganic compound with the chemical formula Na ClO 3 . It is a white crystalline powder that is readily soluble in water. It is hygroscopic . It decomposes above 300 °C to release oxygen [ 4 ] and leaves sodium chloride . Several hundred million tons are produced annually, mainly for applications in bleaching pulp to produce high brightness paper . [ 7 ]
Industrially, sodium chlorate is produced by the electrolysis of concentrated sodium chloride solutions. All other processes are obsolete. The sodium chlorate process is not to be confused with the chloralkali process , which is an industrial process for the electrolytic production of sodium hydroxide and chlorine gas.
The overall reaction can be simplified to the equation:
First, chloride is oxidised to form intermediate hypochlorite , ClO − , which undergoes further oxidation to chlorate along two competing reaction paths: (1) Anodic chlorate formation at the boundary layer between the electrolyte and the anode, and (2) Autoxidation of hypochlorite in the bulk electrolyte.
Under electrolysis hydrogen and sodium hydroxide are formed at the cathode and chloride ions are discharged at the anode ( mixed metal oxide electrode is often used). The evolved chlorine does not escape as a gas but undergoes hydrolysis:
The hydrolysis of chlorine is considered to be fast. The formation of H + ions should make the boundary layer at the anode strongly acidic and this is observed at low chloride concentrations. However, large concentrations of chloride, as they occur in industrial chlorate cells, shift the hydrolysis equilibrium to the left. At the boundary layer the concentration of H + is not high enough to permit diffusion into the bulk electrolyte. Therefore hydrogen is transported away from the anode mostly as hypochlorous acid rather than H + . The hypochlorous acid dissociates in the bulk electrolyte where the pH is high and the hypochlorite ion diffuses back to the anode. More than two thirds of the hypochlorite is consumed by buffering before reaching the anode. The remainder is discharged at the anode to form chlorate and oxygen:
The autoxidation of hypochlorous acid in the bulk electrolyte proceeds according to the simplified overall equation:
It is preceded by the dissociation of a part of the hypochlorous acid involved:
The reaction requires a certain distance from the anode to occur to a significant degree, where the electrolyte is sufficiently buffered by the hydroxyl formed at the cathode. The hypochlorite then reacts with the rest of the acid:
In addition to anode distance the autoxidation also depends on temperature and pH. A typical cell operates at temperatures between 80 °C and 90 °C and at a pH of 6.1–6.4.
Independent of the reaction route the discharge of 6 mol of chloride is required to yield 1 mol of chlorate. However, the anodic oxidation route requires 50% additional electric energy. Therefore, industrial cells are optimised to favour autoxidation. Chlorate formation at the anode is treated as a loss reaction and is minimised by design.
Other loss reactions also decrease the current efficiency and must be suppressed in industrial systems. The main loss occurs by the back reduction of hypochlorite at the cathode. The reaction is suppressed by the addition of a small amount of dichromate (1–5 g/L) to the electrolyte. A porous film of chromium hydroxide is formed by cathodic deposition. The film impedes the diffusion of anions to the cathode, whereas the access of cations and their reduction is facilitated. The film stops growing on its own after it reaches a certain thickness. [ 7 ]
The main commercial use for sodium chlorate is for making chlorine dioxide (ClO 2 ). The largest application of ClO 2 , which accounts for about 95% of the use of chlorate, is in bleaching of pulp. All other, less important chlorates are derived from sodium chlorate, usually by salt metathesis with the corresponding chloride. All perchlorate compounds are produced industrially by the oxidation of solutions of sodium chlorate by electrolysis. [ 7 ]
Sodium chlorate is used as a non-selective herbicide . It is considered phytotoxic to all green plant parts. It can also kill through root absorption.
Sodium chlorate may be used to control a variety of plants including morning glory , canada thistle , johnson grass , bamboo , ragwort , and St John's wort . The herbicide is mainly used on non-crop land for spot treatment and for total vegetation control on areas including roadsides, fenceways, and ditches. Sodium chlorate is also used as a defoliant and desiccant for:
If used in combination with atrazine , it increases the persistence of the effect. If used in combination with 2,4-D , performance is improved. Sodium chlorate has a soil sterilant effect. Mixing with other herbicides in aqueous solution is possible to some extent, so long as they are not susceptible to oxidation.
The sale of sodium chlorate as a weedkiller was banned in the European Union in 2009 citing health dangers, with existing stocks to be used within the following year. [ 8 ]
Chemical oxygen generators , such as those in commercial aircraft, provide emergency oxygen to passengers to protect them from drops in cabin pressure. Oxygen is generated by high-temperature decomposition of sodium chlorate: [ 9 ]
Heat required to initiate this reaction is generated by oxidation of a small amount of iron powder mixed with the sodium chlorate, and the reaction consumes less oxygen than is produced. Barium peroxide ( Ba O 2 ) is used to absorb the chlorine that is a minor product in the decomposition. [ 10 ] An ignitor charge is activated by pulling on the emergency mask. Similarly, the Solidox welding system used pellets of sodium chlorate mixed with combustible fibers to generate oxygen.
Sodium chlorate can be mixed with sucrose sugar to make a highly energetic fuel, similar to that of gunpowder , that burns in airtight spaces. This is the reaction:
However this sodium chlorate is mostly replaced by potassium chlorate . [ citation needed ]
Sodium chlorate can be used with hydrochloric acid (or also sulfuric acid and sodium chloride , the reaction of which generates HCl) to chlorinate aromatic compounds without the use of organic solvents. In this case its function is to oxidize the HCl to obtain either HOCl or Cl 2 (depending upon the pH) in-situ which are the active chlorinating agents. [ 11 ]
When combined with a vanadium pentoxide catalyst, it serves as an oxidant for a variety of organic compounds. Examples include the oxidation of hydroquinone to quinone , [ 12 ] and of furfural to a mixture of maleic and fumaric acid . [ 13 ]
Sodium chlorate is toxic: "doses of a few grams of chlorate are lethal". [ 7 ] (ld50 oral in rats 1200mg /kg) The oxidative effect on hemoglobin leads to methaemoglobin formation, which is followed by denaturation of the globin protein and a cross-linking of erythrocyte membrane proteins with resultant damage to the membrane enzymes. This leads to increased permeability of the membrane, and severe hemolysis . The denaturation of hemoglobin overwhelms the capacity of the G6PD metabolic pathway . In addition, this enzyme is directly denatured by chlorate.
Acute severe hemolysis results, with multi-organ failure , including DIC and kidney failure . In addition there is a direct toxicity to the proximal renal tubule . [ 14 ] The treatment will consist of exchange transfusion , peritoneal dialysis or hemodialysis . [ 15 ]
Sodium chlorate comes in dust , spray and granule formulations. Mixtures of chlorates and organic compounds pose a severe risk of explosions [ 16 ]
Marketed formulations contain a fire retardant . Most commercially available chlorate weedkillers contain approximately 53% sodium chlorate with the balance being a fire depressant such as sodium metaborate or ammonium phosphates .
Sodium chlorate is the active ingredient in a variety of commercial herbicides. Some trade names for products containing sodium chlorate include Atlacide, Defol, De-Fol-Ate, Drop-Leaf, Fall, Harvest-Aid, Kusatol, Leafex, and Tumbleaf. The compound may be used in combination with other herbicides such as atrazine, 2,4-D, bromacil , diuron , and sodium metaborate.
Sodium chlorate was an extensively used weed killer within the EU, until 2009 when it was withdrawn after a decision made under terms of EU Regulations. Its use as a herbicide outside the EU remains unaffected, as does its use in other non-herbicidal applications, such as in the production of chlorine dioxide biocides and for pulp and paper bleaching.
Historian James Watson of Massey University in New Zealand wrote a widely reported article, "The Significance of Mr. Richard Buckley's Exploding Trousers " [ 17 ] [ 18 ] about accidents with sodium chlorate when used as a herbicide to control ragwort in the 1930s. [ 19 ] This later won him an Ig Nobel Prize in 2005, [ 20 ] and was the basis for the May 2006 "Exploding Pants" episode of MythBusters . | https://en.wikipedia.org/wiki/NaClO3 |
Sodium perchlorate is an inorganic compound with the chemical formula Na Cl O 4 . It consists of sodium cations Na + and perchlorate anions ClO − 4 . It is a white crystalline, hygroscopic solid that is highly soluble in water and ethanol . It is usually encountered as sodium perchlorate monohydrate NaClO 4 ·H 2 O . The compound is noteworthy as the most water-soluble of the common perchlorate salts.
Sodium perchlorate and other perchlorates have been found on the planet Mars , having first been detected by the NASA probe Phoenix in 2009. This was later confirmed by spectral analysis by the Mars Reconnaissance Orbiter in 2015 of what is thought to be brine seeps which may be the first evidence of flowing liquid water containing hydrated salts on Mars. [ 1 ] [ 2 ]
Its heat of formation is −382.75 kJ/mol, i.e. it is thermally stable up to high temperatures. At 490 °C it undergoes thermal decomposition, producing sodium chloride and dioxygen . [ 3 ] It crystallizes in the rhombic crystal system . [ 4 ]
Perchloric acid is made by treating NaClO 4 with HCl. [ 5 ] Ammonium perchlorate and potassium perchlorate , of interest in rocketry and pyrotechnics, are prepared by double decomposition from a solution of sodium perchlorate and ammonium chloride or potassium chloride , respectively.
Because of its high solubility (2096 g/L at 25 °C) and the inert behaviour of dissolved perchlorate, solutions of NaClO 4 are often used as unreactive background electrolyte ( supporting electrolyte ). Indeed, because the reduction reaction of perchlorate is kinetically limited even if it is a thermodynamically unstable compound, perchlorate is a redox non-sensitive anion . It is also a non- complexing anion with a fairly low ligand binding capacity.
In the past perchlorates were quite widely used in the synthesis of coordination compounds because their larger size (compared to halides) and excellent hydrogen bonding abilities made them highly effective counter-ions for complexes with ammine, aquo and halido ligands, often yielding highly crystalline products. However because of the hazards (see Safety Section below) associated with their use they have been largely superseded in most labs by much less risky counterions like fluoroborate (BF 4 – , PF 6 – and related anions.
Sodium perchlorate is the precursor to ammonium, potassium and lithium perchlorate salts, often taking advantage of their low solubility in water relative to NaClO 4 (209 g/(100 mL) at 25 °C). [ 6 ]
It is used for denaturating proteins in biochemistry and in standard DNA extraction and hybridization reactions in molecular biology .
Sodium perchlorate can be used to block iodine uptake before administration of iodinated contrast agents in patients with subclinical hyperthyroidism (suppressed TSH ). [ 7 ]
Sodium perchlorate is produced by anodic oxidation of sodium chlorate ( NaClO 3 ) at an inert electrode , such as platinum . [ 5 ]
All perchlorates are potent oxidisers. When mixed with organic compounds or powdered metals like aluminum, extreme combustion reactions can result, hence the use of such materials in fireworks, low tech rocket propellants and improvised explosives. Because of their kinetic inertness mixtures of perchlorate with organic compounds or powdered metals do not ignite/detonate spontaneously and are shock insensitive.
Acute toxicity : The median lethal dose (LD 50 ) is 2 – 4 g/kg (rabbits, oral). [ 5 ]
Chronic toxicity : The frequent consumption of drinking water with low concentrations (in the range of μg/L, ppb ) of perchlorate is harmful for the thyroid gland as the perchlorate anion competes with the uptake of iodide severely disrupting thyroid function.
Environmental effects: Perchlorate anions are regarded as persistent pollutants that can cause long term contamination of drinking water and NaClO4's high solubility makes it highly mobile in the environment. Significant concerns have been raised about the environmental impacts of perchlorates because of its ability to disrupt iodide uptake and metabolism. [ 8 ] | https://en.wikipedia.org/wiki/NaClO4 |
Sodium dodecyl sulfate ( SDS ) or sodium lauryl sulfate ( SLS ), sometimes written sodium laurilsulfate , is an organic compound with the formula CH 3 (CH 2 ) 11 OSO 3 Na and structure H 3 C − (CH 2 ) 11 −O− S(=O) 2 −O − Na + . It is an anionic surfactant used in many cleaning and hygiene products. This compound is the sodium salt of the 12-carbon organosulfate . Its hydrocarbon tail combined with a polar " headgroup " give the compound amphiphilic properties that make it useful as a detergent . SDS is also component of mixtures produced from inexpensive coconut and palm oils . SDS is a common component of many domestic cleaning, personal hygiene and cosmetic, pharmaceutical, and food products, as well as of industrial and commercial cleaning and product formulations. [ 2 ]
The critical micelle concentration (CMC) in water at 25 °C is 8.2 mM, [ 1 ] and the aggregation number at this concentration is usually considered to be about 62. [ 3 ] The micelle ionization fraction (α) is around 0.3 (or 30%). [ 4 ]
SDS is mainly used in detergents for laundry with many cleaning applications. [ 5 ] It is a highly effective surfactant and is used in any task requiring the removal of oily stains and residues. For example, it is found in higher concentrations with industrial products including engine degreasers, floor cleaners, and car exterior cleaners. [ citation needed ]
It is a component in hand soap, toothpastes, shampoos, shaving creams, and bubble bath formulations, for its ability to create a foam (lather), for its surfactant properties, and in part for its thickening effect. [ 6 ]
Sodium dodecyl sulfate, appearing as its synonym sodium lauryl sulfate (SLS), is considered a generally recognized as safe (GRAS) ingredient for food use according to the USFDA (21 CFR 172.822). [ 7 ] It is used as an emulsifying agent and whipping aid. [ 8 ] As an emulsifier in or with egg whites the United States Code of Federal Regulations require that it must not exceed 1,000 parts per million (0.1%) in egg white solids or 125 parts per million (0.0125%) in frozen or liquid egg whites and as a whipping agent for the preparation of marshmallows it must not exceed 0.5% of the weight of gelatine. [ 9 ] SLS is reported to temporarily diminish perception of sweetness. [ 10 ]
SDS is used in cleaning procedures, [ 11 ] and is commonly used as a component for lysing cells during RNA extraction or DNA extraction , inhibiting the activity of nucleases, enzymes that can degrade DNA, protecting the integrity of the isolated genetic material, and for denaturing proteins in preparation for electrophoresis in the SDS-PAGE technique. [ 12 ]
In the case of SDS-PAGE, the compound works by disrupting non-covalent bonds in the proteins, and so denaturing them, i.e. causing the protein molecules to lose their native conformations and shapes. By binding to proteins at a ratio of one SDS molecule per 2 amino acid residues, the negatively charged detergent provides all proteins with a similar net negative charge and therefore a similar charge-to-mass ratio. [ 13 ] In this way, the difference in mobility of the polypeptide chains in the gel can be attributed solely to their length as opposed to both their native charge and shape. [ 13 ] [ 14 ] This separation based on the size of the polypeptide chain simplifies the analysis of protein molecules. [ 15 ]
Sodium lauryl sulfate is a widely used in the pharmaceutical field as an ionic solubilizer and emulsifier that is suitable for applications in liquid dispersions, solutions, emulsions and micro emulsions, tablets, foams and semi-solids such as creams, lotions and gels. [ 16 ] Additionally, SLS aids in tablet wettability, as well as lubrication during manufacturing. Brand names of pharma-grade SLS include Kolliphor SLS and Kolliphor SLS Fine. [ 17 ]
SLS is used in an improved technique for preparing brain tissues for study by optical microscopy. The technique, which has been branded as CLARITY, was the work of Karl Deisseroth and coworkers at Stanford University , and involves infusion of the organ with an acrylamide solution to bind the macromolecules of the organ ( proteins , nucleic acids , etc.), followed by thermal polymerization to form a "brain–hydrogel" (a mesh interspersed throughout the tissue to fix the macromolecules and other structures in space), and then by lipid removal using SDS to eliminate light scattering with minimal protein loss, rendering the tissue quasi-transparent. [ 18 ] [ 19 ]
Along with sodium dodecylbenzene sulfonate and Triton X-100 , aqueous solutions of SDS are popular for dispersing or suspending nanotubes, such as carbon nanotubes . [ 20 ]
SLS has been proposed as a potentially effective topical microbicide, for intravaginal use, to inhibit and possibly prevent infection by various enveloped and non-enveloped viruses such as the herpes simplex viruses , HIV , and the Semliki Forest virus . [ 21 ] [ 22 ]
Liquid membranes formed from SDS in water have been demonstrated to work as unusual particle separators. [ 23 ] The device acts as a reverse filter, allowing large particles to pass while capturing smaller particles.
Dodecyl alcohol is sulfated using sulfur trioxide . The reaction proceeds by initial formation of the pyrosulfate:
Several million tons are produced annually. [ 2 ]
SDS can also be synthesized by treating lauryl alcohol with chlorosulfuric acid . [ 24 ] The resulting half ester of sulfuric acid is then neutralized with alkali.
Lauryl alcohol can be used in pure form or as a mixtures of fatty alcohols. When produced from these sources, "SDS" products are a mixture of various sodium alkyl sulfates with SDS being the main component. [ 25 ] For instance, SDS is a component, along with other chain-length amphiphiles , when produced from coconut oil, and is known as sodium coco sulfate (SCS). [ 26 ] SDS is available commercially in powder, pellet, and other forms (each differing in rates of dissolution), as well as in aqueous solutions of varying concentrations. [ citation needed ]
SDS is not carcinogenic in low concentrations according to some [ clarification needed ] studies. [ 27 ] [ 28 ] Like all detergents , sodium lauryl sulfate removes oils from the skin , and can cause skin and eye irritation. [ citation needed ] It has been shown to irritate the skin of the face, with prolonged and constant exposure (more than an hour) in young adults. [ 29 ] SDS may worsen skin problems in individuals with chronic skin hypersensitivity , with some people being affected more than others. [ 30 ] [ 31 ] [ 32 ]
SDS is a common ingredient in toothpastes due to its low cost, [ 33 ] its lack of impact on taste, [ 33 ] and its desirable action as a foaming agent. [ 33 ]
SDS may reduce the amount of bad breath -causing volatile sulfur compounds (VSCs) in the mouth. [ 34 ] A series of small crossover studies (25–34 patients) have supported the efficacy of SLS in the reduction of VSCs, and its related positive impact on breath malodor, although these studies have been generally noted to reflect technical challenges in the control of study design variables. [ 34 ]
Primary sources from the group of Irma Rantanen at University of Turku , Finland claim that SLS-containing pastes cause more dry mouth ( xerostomia ) than their proposed alternative. However, a 2011 Cochrane review of these studies, and of the more general area, concludes that there "is no strong evidence... that any topical therapy is effective for relieving the symptom of dry mouth." [ 35 ]
A safety concern has been raised on the basis of several studies regarding the effect of toothpaste SDS on aphthous ulcers (more specifically, mouth ulcers or "canker sores"), commonly referred to as canker or white sores. [ 33 ] According to the NHS and Alessandro Villa of the Miami Cancer Institute, SLS is a cause for concern for mouth ulcers. [ 36 ] [ 37 ] [ 38 ] As Lippert notes, of 2013, "very few... marketed toothpastes contain a surfactant other than SLS [SDS]," and leading manufacturers continue to formulate their produce with SDS. [ 33 ] According to Allesandro Villa of the Miami Cancer Institute, one theory is that SLS disrupts the protective layer of mucus covering the mouth. [ 36 ] | https://en.wikipedia.org/wiki/NaDodSO4 |
Sodium fluoride ( NaF ) is an inorganic compound with the formula Na F . It is a colorless or white solid that is readily soluble in water. It is used in trace amounts in the fluoridation of drinking water to prevent tooth decay , and in toothpastes and topical pharmaceuticals for the same purpose. In 2022, it was the 221st most commonly prescribed medication in the United States, with more than 1 million prescriptions. [ 7 ] [ 8 ] It is also used in metallurgy and in medical imaging .
Fluoride salts are often added to municipal drinking water (as well as to certain food products in some countries) for the purpose of maintaining dental health. The fluoride enhances the strength of teeth by the formation of fluorapatite , a naturally occurring component of tooth enamel . [ 9 ] [ 10 ] [ 11 ] Although sodium fluoride is used to fluoridate water and is the standard by which other water-fluoridation compounds are gauged, hexafluorosilicic acid (H 2 SiF 6 ) and its salt sodium hexafluorosilicate (Na 2 SiF 6 ) are more commonly used additives in the United States. [ 12 ]
Fluoride supplementation has been extensively studied for the treatment of postmenopausal osteoporosis . This supplementation does not appear to be effective; even though sodium fluoride increases bone density, it does not decrease the risk of fractures. [ 13 ] [ 14 ]
In medical imaging, fluorine-18 -labelled sodium fluoride ( USP , sodium fluoride Na 18 F) is one of the oldest tracers used in positron emission tomography (PET), having been in use since the 1960s. [ 15 ] Relative to conventional bone scintigraphy carried out with gamma cameras or SPECT systems, PET offers more sensitivity and spatial resolution. Fluorine-18 has a half-life of 110 min, which requires it to be used promptly once produced; this logistical limitation hampered its adoption in the face of the more convenient technetium-99m -labelled radiopharmaceuticals . However, fluorine-18 is generally considered to be a superior radiopharmaceutical for skeletal imaging. In particular it has a high and rapid bone uptake accompanied by very rapid blood clearance, which results in a high bone-to-background ratio in a short time. [ 16 ] Additionally the annihilation photons produced by decay of 18 F have a high energy of 511 keV compared to the 140 keV photons of 99m Tc. [ 17 ]
Sodium fluoride has a variety of specialty chemical applications in synthesis and extractive metallurgy . It reacts with electrophilic chlorides including acyl chlorides , sulfur chlorides, and phosphorus chloride. [ 18 ] Like other fluorides, sodium fluoride finds use in desilylation in organic synthesis . Sodium fluoride can be used to produce fluorocarbons via the Finkelstein reaction ; this process has the advantage of being simple to perform on a small scale but is rarely used on an industrial scale due to the existence of more effective techniques (e.g. Electrofluorination , Fowler process ).
Sodium fluoride is sometimes added at relatively high concentrations (~20 mM) to protein lysis buffers in order to inhibit endogenous phosphatases and thereby protect phosphorylated protein sites. [ 19 ] Sodium pyrophosphate and Sodium orthovanadate are also used for this purpose. [ 20 ]
Inorganic fluorides such as fluorosilicates and sodium fluoride complex magnesium ions as magnesium fluorophosphate . They inhibit enzymes such as enolase that require Mg 2+ as a prosthetic group. Thus, fluoride poisoning prevents phosphate transfer in oxidative metabolism . [ 21 ] Sodium fluoride, patented as an insecticide in 1896, was commonly used through the 1970s on ants and other domestic pests, [ 22 ] and as a stomach poison for plant-feeding insects. [ 23 ]
Its use, along with that of sodium fluorosilicate , declined over the 20th century as the products were banned or restricted due to the possibility of poisoning, intentional or accidental. [ 22 ] In 1942, for instance, 47 inmates at the Oregon State Hospital died after consuming scrambled eggs which had been inadvertently prepared with sodium fluoride; while assisting the cooks, another inmate had confused a container of insecticide—used by the hospital to control cockroaches—with powdered milk, which was stored nearby. [ 24 ]
Sodium fluoride is used as a cleaning agent (e.g., as a " laundry sour "). [ 25 ]
Sodium fluoride can be used in a nuclear molten-salt reactor , which sodium fluoride is used as the reactor's coolant. [ 26 ]
The lethal dose for a 70 kg (154 lb) human is estimated at 5–10 g. [ 25 ]
Fluorides, particularly aqueous solutions of sodium fluoride, are rapidly and quite extensively absorbed by the human body. [ 27 ]
Fluorides interfere with electron transport and calcium metabolism . Calcium is essential for maintaining cardiac membrane potentials and in regulating coagulation . High ingestion of fluoride salts or hydrofluoric acid may result in fatal arrhythmias due to profound hypocalcemia . Chronic over-absorption can cause hardening of bones, calcification of ligaments, and buildup on teeth. Fluoride can cause irritation or corrosion to eyes, skin, and nasal membranes. [ 28 ]
Sodium fluoride is classed as toxic by both inhalation (of dusts or aerosols) and ingestion . [ 29 ] In high enough doses, it has been shown to affect the heart and circulatory system. For occupational exposures, the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have established occupational exposure limits at 2.5 mg/m 3 over an eight-hour time-weighted average. [ 30 ]
In the higher doses used to treat osteoporosis , plain sodium fluoride can cause pain in the legs and incomplete stress fractures when the doses are too high; it also irritates the stomach, sometimes so severely as to cause peptic ulcer disease . Slow-release and enteric-coated versions of sodium fluoride do not have significant gastric side effects, and have milder and less frequent complications in the bones. [ 31 ] In the lower doses used for water fluoridation, the only clear adverse effect is dental fluorosis , which can alter the appearance of children's teeth during tooth development . A chronic fluoride ingestion of 1 ppm of fluoride in drinking water can cause mottling of the teeth (fluorosis) and an exposure of 1.7 ppm will produce mottling in 30%–50% of patients. [ 27 ] Studies have shown that dental fluorosis negatively impacts the self-esteem and self-image of adolescents. [ 32 ] [ 33 ]
Sodium fluoride is an inorganic ionic compound , dissolving in water to give separated Na + and F − ions. Like sodium chloride , it crystallizes in a cubic motif where both Na + and F − occupy octahedral coordination sites ; [ 34 ] [ 35 ] its lattice spacing, approximately 462 pm , is smaller than that of sodium chloride (564 pm).
The mineral form of NaF, villiaumite , is moderately rare. It is known from plutonic nepheline syenite rocks. [ 36 ]
NaF is prepared by neutralizing hydrofluoric acid or hexafluorosilicic acid (H 2 SiF 6 ), both byproducts of the reaction of fluorapatite (Ca 5 (PO 4 ) 3 F) from phosphate rock during the production of superphosphate fertilizer. Neutralizing agents include sodium hydroxide and sodium carbonate . Alcohols are sometimes used to precipitate the NaF: [ 25 ]
From solutions containing HF, sodium fluoride precipitates as the bifluoride salt sodium bifluoride (NaHF 2 ). Heating the latter releases HF and gives NaF.
In a 1986 report, the annual worldwide consumption of NaF was estimated to be several million tonnes. [ 25 ] | https://en.wikipedia.org/wiki/NaF |
Sodium fluoroacetate , also known by its trade name as a mammal poison compound 1080 , is an organofluorine chemical compound with the chemical formula F C H 2 C O 2 Na . It is the sodium salt of fluoroacetic acid , and contains sodium cations Na + and fluoroacetate anions FCH 2 CO − 2 . A colourless salt with a taste similar to table salt ( sodium chloride ), it is used under the name "1080" to kill small and medium mammals, including rodents . New Zealand is the world's biggest user of 1080, particularly to kill introduced brushtail possums , often with aerial spraying.
Fluoroacetate occurs naturally in at least 40 plants in Australia , Brazil , and Africa . It is one of only five known organofluorine -containing natural products. [ 3 ]
Gastrolobium is a genus of flowering plants in the family Fabaceae . This genus consists of over 100 species, and all but two are native to the southwest region of Western Australia , where they are known as "poison peas". Gastrolobium growing in southwestern Australia concentrate fluoroacetate from low- fluoride soils . [ 4 ] Brushtail possums , bush rats , and western grey kangaroos native to this region are capable of safely eating plants containing fluoroacetate, but livestock and introduced species from elsewhere in Australia are highly susceptible to the poison , [ 5 ] as are species introduced from outside Australia, such as the red fox . The fact that many Gastrolobium species also have high secondary toxicity to non-native carnivores is thought to have limited the ability of cats to establish populations in locations where the plants form a major part of the understorey vegetation . [ 6 ]
The presence of Gastrolobium species in Western Australia has often forced farmers to 'scalp' their land, that is, remove the top soil and any poison pea seed which it may contain, and replace it with a new poison pea-free top soil sourced from elsewhere in which to sow crops. Similarly, after bushfires in north-western Queensland , cattlemen have to move livestock before the poisonous Gastrolobium grandiflorum emerges from the ashes. [ 7 ]
The related compound potassium fluoroacetate occurs naturally as a defensive compound in at least 40 plant species in Australia , New Zealand , [ 8 ] [ 9 ] Brazil , and Africa . It was first identified in Dichapetalum cymosum , commonly known as gifblaar or poison leaf, by Marais in 1944. [ 10 ] [ 11 ] As early as 1904, colonists in Sierra Leone used extracts of Chailletia toxicaria , which also contains fluoroacetic acid or its salts, to poison rats. [ 12 ] [ 13 ] [ 14 ] Several native Australian plant genera contain the toxin, including Gastrolobium , Gompholobium , Oxylobium , Nemcia , and Acacia . New Zealand's native Puha contains 1080 in very low concentrations. [ 15 ]
X-ray crystallography confirms that solid sodium fluoroacetate is a salt with intact fluoroacetate anions interacting with Na + via a network of Na-O bonds.
Sodium fluoroacetate is toxic to most obligate aerobic organisms, and highly toxic to mammals and insects. [ 16 ] The oral dose of sodium fluoroacetate sufficient to be lethal in humans is 2–10 mg/kg. [ 17 ]
The toxicity varies with species. The New Zealand Food Safety Authority established lethal doses for a number of species. Dogs, cats, and pigs appear to be most susceptible to poisoning. [ 18 ]
The enzyme fluoroacetate dehalogenase has been discovered in a soil bacterium , which can detoxify fluoroacetate in the surrounding medium. [ 19 ]
Fluoroacetate is structurally similar to acetate , which has a pivotal role in cellular metabolism. This similarity is the basis of the toxicity of fluoroacetate. Two related mechanisms for its toxicity have been discussed, with both beginning with the conversion of fluoroacetate to 2-fluorocitrate. 2-Fluorocitrate arises by condensation with oxaloacetate with fluoroacetyl coenzyme A , catalyzed by citrate synthase . Fluorocitrate binds very tightly to aconitase , thereby halting the citric acid cycle . This inhibition results in an accumulation of citrate in the blood. Citrate and fluorocitrate are allosteric inhibitors of phosphofructokinase-1 (PFK-1), a key enzyme in glycolysis . When PFK-1 is inhibited, cells are no longer able to metabolize carbohydrates, depriving them of energy. [ 16 ] Alternatively, fluorocitrate interferes with citrate transport in the mitochondria. [ 20 ]
In humans, the symptoms of poisoning normally appear between 30 minutes and three hours after exposure. Initial symptoms typically include nausea, vomiting, and abdominal pain; sweating, confusion, and agitation follow. In significant poisoning, cardiac abnormalities including tachycardia or bradycardia , hypotension , and ECG changes develop. Neurological effects include muscle twitching and seizures; consciousness becomes progressively impaired after a few hours leading to coma . Death is normally due to ventricular arrhythmias , progressive hypotension unresponsive to treatment, and aspiration pneumonia . [ 16 ]
Symptoms in domestic animals vary: dogs tend to show nervous system signs such as convulsions, vocalization, and uncontrollable running, while large herbivores such as cattle and sheep more predominantly show cardiac signs. [ 21 ]
Sub-lethal doses of sodium fluoroacetate may cause damage to tissues with high energy needs, especially the brain , gonads , heart , lungs . Fetuses are also highly susceptible. Sub-lethal doses are typically completely metabolised and excreted within four days. [ 22 ]
Effective antidotes are unknown. Research in monkeys has shown that the use of glyceryl monoacetate can prevent problems if given after ingestion of sodium fluoroacetate, and this therapy has been tested in domestic animals with some positive results. In theory, glyceryl monoacetate supplies acetate ions to allow continuation of cellular respiration which the sodium fluoroacetate had disrupted. [ 23 ]
Experiments of N. V. Goncharov and co-workers resulted in development of two varieties of potentially successful [ quantify ] treatments. One combines a phenothiazine compound and a dioic acid compound. [ vague ] The other includes a phenothiazine compound, a nitroester compound, [ vague ] and ethanol . [ 24 ] [ 25 ]
In clinical cases, use of muscle relaxants , anti-convulsants , mechanical ventilation , and other supportive measures may all be required. Few animals or people have been treated successfully after significant sodium fluoroacetate ingestions. [ 26 ]
Animals can tolerate varying amounts of fluoroacetate. Mammalian carnivores and rodents tend to be the least tolerant, followed by mammalian herbivores, reptiles and amphibians, and finally fish. A lower metabolic rate seems to help with poison tolerance in general. [ 27 ]
Many animals native to Australia seem to have developed additional tolerance to fluoroacetate beyond what general trends predict. Herbivore, seed-eating birds are exposed to very high amounts of natural fluoroacetate with no ill effect. Emus living in areas where fluoroacetate-producing plants grow can tolerate 150 times the concentration compared to emus living outside. Some native insects tolerate fluoroacetate and repurpose it as a defense chemical against carnivores. [ 27 ]
Fluoacetate tolerance can be acquired in animals, though it is not fully clear how. [ 27 ] In one study, sheep gut bacteria were genetically engineered to contain the fluoroacetate dehalogenase enzyme that inactivates sodium fluoroacetate. The bacteria were administered to sheep, who then showed reduced signs of toxicity after sodium fluoroacetate ingestion. [ 28 ] A strain of natural bacterium that does the same was isolated from cattle rumen in 2012. [ 27 ]
The effectiveness of sodium fluoroacetate as a rodenticide was reported in 1942. [ 29 ] The salt is synthesized by treating sodium chloroacetate with potassium fluoride . [ 30 ] Both sodium and potassium salts are derivatives of fluoroacetic acid . The name "1080" refers to the catalogue number of the poison, which became its brand name. [ 16 ]
Sodium fluoroacetate is used as a pesticide , especially for mammalian pest species. The agricultural industry uses 1080 to kill herbivorous mammals to stop them from eating pasture plants and crops. In New Zealand and Australia it is also used to control introduced, invasive non-native mammals that prey on or compete with native wildlife and vegetation.
In Australia, sodium fluoroacetate was first used in rabbit control programmes in the early 1950s, where it is regarded as having "a long history of proven effectiveness". [ 31 ] It is seen as a critical component of the integrated pest-control programmes for rabbits , foxes , wild dogs, and feral pigs. Since 1994, broad-scale fox control using 1080 meat baits in Western Australia has significantly improved the population numbers of several native species and led, for the first time, to three species of mammals being taken off the state's endangered species list. In Australia, minor direct mortality of native animal populations from 1080 baits is regarded as acceptable by the regulatory bodies, compared to the predatory and competitive effects of those introduced species being managed using 1080. [ 32 ] 1080 is also used by the agricultural industry to destroy populations of Dingos , Australia's only pre-colonial mammalian apex predator, a practice condemned by numerous conservation groups and wildlife experts around the continent due to its far-reaching destabilisation of the natural balance of the ecosystem. [ 33 ]
Western Shield is a project to boost populations of endangered mammals in south-west Australia conducted by the Department of Environment and Conservation of Western Australia . The project entails distributing fluoroacetate-baited meat from the air to kill predators . Wild dogs and foxes will readily eat the baited meat. Cats pose a greater difficulty as they are generally not interested in scavenging. However, an Australian RSPCA -commissioned study criticized 1080, calling it an inhumane killer. [ 34 ] Some Western Australian herbivores (notably, the local subspecies of the tammar wallaby , Macropus eugenii derbianus , but not the subspecies M. e. eugenii of southern Australia and M. e. decres on Kangaroo Island ) have, by natural selection , developed partial immunity to the effects of fluoroacetate, [ 35 ] so that its use as a poison may reduce collateral damage to some native herbivores specific to that area.
In 2011, over 3,750 toxic baits containing 3 ml of 1080 were laid across 520 properties over 48,000 hectares (120,000 acres) between the Tasmanian settlements of Southport and Hobart as part of an ongoing attempt at the world's biggest invasive animal eradication operation – the eradication of red foxes [ 36 ] from the island state. The baits were spread at the rate of one per 10 hectares and were buried, to mitigate the risk to non-target wildlife species like Tasmanian devils . [ 37 ] Native animals are also targeted with 1080. [ 38 ] During May 2005 up to 200,000 Bennett's wallabies on King Island were intentionally killed in one of the largest coordinated 1080 poisonings seen in Tasmania. [ 39 ] [ 40 ]
In 2016, PAPP (para-amino propiophenone) became available for use, which the RSPCA has endorsed as an alternative to 1080, due in part to its ability to kill faster and cause less suffering, as well as having an antidote, which 1080 does not. [ 41 ] However, as of June 2023 [update] , 1080 was still being used in attempts to reduce feral cat populations. [ 42 ]
Worldwide, New Zealand is the largest user of sodium fluoroacetate. [ 17 ] This high usage is attributable to the fact that, apart from two species of bat, [ 43 ] New Zealand has no native land mammals, and some of those that have been introduced have had devastating effects on vegetation and native species.
1080 is used to control possums , rats , stoats , deer , and rabbits . [ 44 ] The largest users, despite some vehement opposition, [ 45 ] are OSPRI New Zealand and the Department of Conservation . [ 46 ]
Sodium fluoroacetate is used in the United States to kill coyotes . [ 47 ] Prior to 1972 when the EPA cancelled all uses, sodium fluoroacetate was used much more widely as a cheap [ 48 ] predacide and rodenticide ; in 1985, the restricted-use "toxic collar" approval was finalized. [ 49 ]
1080 is used as a rodenticide in Mexico, Japan, Korea, and Israel. [ 16 ] [ 50 ] In Israel 0.05% sodium fluoroacetate whole wheat grain baits are used to prevent heavy crop loss to field crops during mass outbreaks of the field rodents Microtus guentheri , Meriones tristrami and Mus musculus populations. [ 51 ]
Because 1080 is highly water-soluble, it will be dispersed and diluted in the environment by rain, stream water, and ground water. Sodium fluoroacetate at the concentrations found in the environment after standard baiting operations will break down in natural water containing living organisms, such as aquatic plants or micro-organisms. Water-monitoring surveys, conducted during the 1990s, have confirmed that significant contamination of waterways following aerial application of 1080 bait is possible, but unlikely. [ 52 ] Research by NIWA showed that 1080 deliberately placed in small streams for testing was undetectable at the placement site after 8 hours, as it washed downstream. Testing was not done downstream. [ 53 ]
In New Zealand, surface water is routinely monitored after aerial application of 1080, and water samples are collected immediately after application, when there is the highest possibility of detecting contamination. [ 54 ] Of 2442 water samples tested in New Zealand between 1990 and 2010, following aerial 1080 operations: 96.5% had no detectable 1080 at all and, of all the samples, only six were equal to, or above the Ministry of Health level for drinking water, and none of these came from drinking water supplies. [ 55 ] Of 592 samples taken from human or stock drinking supplies, only four contained detectable 1080 residues at 0.1ppb (1 sample) and 0.2 ppb (3 samples) – all well below the Ministry of Health level of 2 ppb.
In an experiment funded by the Animal Health Board and conducted by NIWA simulating the effects of rainfall on 1080 on a steep soil-covered hillside a few meters from a stream, it was found that 99.9% of the water containing 1080 leached straight into the soil (See 4.3 of [ 56 ] ) and did not flow over the ground to the stream as had been expected. The experiment also measured contamination of soil water, which was described as the water carried through the soil underground at short horizontal distances (0.5-3m), downhill toward the stream. The experiment did not measure contamination of deeper soil and ground water immediately beneath the site of application. [ 56 ]
The fate of 1080 in the soil has been established by research defining the degradation of naturally occurring fluoroacetate (Oliver, 1977). Sodium fluoroacetate is water-soluble, and residues from uneaten baits leach into the soil where they are degraded to non-toxic metabolites by soil microorganisms, including bacteria ( Pseudomonas ) and the common soil fungus ( Fusarium solani ) (David and Gardiner, 1966; Bong, Cole and Walker, 1979; Walker and Bong, 1981). [ 57 ]
Although it is now infrequent, individual aerial 1080 operations can still sometimes affect local bird populations if not carried out with sufficient care. In New Zealand, individuals from 19 species of native birds and 13 species of introduced birds have been found dead after aerial 1080 drops. Most of these recorded bird deaths were associated with only four operations in the 1970s that used poor-quality carrot baits with many small fragments. [ 58 ] On the other hand, many native New Zealand bird populations have been successfully protected by reducing predator numbers through aerial 1080 operations. Kōkako , blue duck , [ 59 ] New Zealand pigeon , [ 60 ] kiwi , [ 61 ] kaka , [ 62 ] New Zealand falcon , [ 63 ] tomtit , [ 64 ] South Island robin , [ 65 ] North Island robin , [ 66 ] New Zealand parakeets ( kākāriki ), and yellowhead [ 67 ] have all responded well to pest control programmes using aerial 1080 operations, with increased chick and adult survival, and increases in population size. In contrast, seven of 38 tagged kea , the endemic alpine parrot, were killed [ 68 ] during an aerial possum control operation on the West Coast in August 2011. Because of their omnivorous feeding habits and inquisitive behaviour, kea are known to be particularly susceptible to 1080 poison baits, as well as other environmental poisons like the zinc and lead used in the flashings of backcountry huts and farm buildings. [ 69 ] Recent research found that proximity to human-occupied sites where kea scrounge human food is inversely related to survival; the odds of survival increased by a factor of 6.9 for remote kea compared to those that lived near scrounging sites. High survival in remote areas is explained by innate neophobia and a short field-life of prefeed baits, which together preclude acceptance of poison baits as familiar food. [ 70 ]
Reptiles and amphibians are susceptible to 1080, although much less sensitive than mammals . [ 71 ] Amphibian and reptile species that have been tested in Australia are generally more tolerant to 1080 poison than are most other animals. [ 72 ] McIlroy (1992) calculated that even if lizards fed entirely on insects or other animals poisoned with 1080, they could never ingest enough poison to receive a lethal dose. [ 73 ] Laboratory trials in New Zealand simulating worst-case scenarios indicate that both Leiopelma archeyi ( Archey's frog ) and L. hochstetteri ( Hochstetter's frog ) can absorb 1080 from contaminated water, substrate, or prey. The chance of this occurring in the wild is ameliorated by a variety of factors, including frog ecology. Captive maintenance and contamination problems rendered parts of this study inconclusive. Further population monitoring is recommended to provide more conclusive evidence than provided by this single study. [ 74 ] In New Zealand, the secondary poisoning of feral cats and stoats following 1080 operations is likely to have a positive effect on the recovery of native skink and gecko populations. [ 75 ] [ 76 ] [ 77 ] : 257 Killing rabbits [ 78 ] and possums, [ 79 ] which compete for food with skinks and geckos, may also have benefits.
Fish generally have very low sensitivity to 1080. Toxicity tests have been conducted in the US on bluegill sunfish, rainbow trout , and the freshwater invertebrate Daphnia magna . Tests at different 1080 concentrations on sunfish (for four days) and Daphnia (two days) showed that 1080 is "practically non-toxic" (a US EPA classification) to both these species. Rainbow trout were also tested over four days at four concentrations ranging from 39 to 170 mg 1080 per litre. From these results an LC50 (the concentration of 1080 per litre of water which theoretically kills 50% of the test fish) can be calculated. The LC50 for rainbow trout was calculated to be 54 mg 1080/litre – far in excess of any known concentration of 1080 found in water samples following 1080 aerial operations. Thus 1080 is unlikely to cause mortality in freshwater fish. [ 80 ]
Insects are susceptible to 1080 poisoning. Some field trials in New Zealand have shown that insect numbers can be temporarily reduced within 20 cm of toxic baits, but numbers return to normal levels within six days of the bait being removed. [ 81 ] Other trials have found no evidence that insect communities are negatively affected. [ 82 ] Another New Zealand study showed that wētā , native ants, and freshwater crayfish excrete 1080 within one to two weeks. [ 83 ] There is also evidence that 1080 aerial operations in New Zealand can benefit invertebrate species. [ 84 ] Both possums and rats are a serious threat to endemic invertebrates in New Zealand, where around 90 per cent of spiders and insects are endemic and have evolved without predatory mammals. [ 85 ] In a study on the diet of brushtail possums, 47.5 per cent of possum faeces examined between January 1979 and June 1983 contained invertebrates, mostly insects. [ 86 ] One possum can eat up to 60 endangered native land snails ( Powelliphanta spp.) in one night. [ 87 ] | https://en.wikipedia.org/wiki/NaFC2H2O2 |
NaGISA ( Natural Geography in Shore Areas or Natural Geography of In-Shore Areas ) is an international collaborative effort aimed at inventorying, cataloguing, and monitoring biodiversity of the in-shore area . So named for the Japanese word "nagisa" ("where the land meets the sea"), it is an Apronym . NaGISA is the first project of the larger CoML effort ( Census of Marine Life ) to have global participation in actual field work. The actual procedures of this project involve inexpensive collection equipment (for easy universal participation). This equipment is used to photograph sampling sites, to actually take samples from the sites, and to process these samples. At each site throughout the world, samples are taken from the intertidal zone out to a depth of 10 meters (and optionally out to 20 meters depth). These samples are then processed (the organisms are isolated) and then analyzed and catalogued. The information (regarding the kind and number of organisms analyzed) is sent to the global headquarters of NaGISA- the University of Kyoto in Japan. All of this information is then collated on the Ocean Biogeographic Information System ( OBIS website ). The end goal of the larger CoML effort is to find what was , what is , and what will be in the world's oceans. For NaGISA the goal is to find this in the world's in-shore areas. [ 1 ] | https://en.wikipedia.org/wiki/NaGISA |
Sodium hydride is the chemical compound with the empirical formula Na H . This alkali metal hydride is primarily used as a strong yet combustible base in organic synthesis . NaH is a saline (salt-like) hydride , composed of Na + and H − ions, in contrast to molecular hydrides such as borane , silane , germane , ammonia , and methane . It is an ionic material that is insoluble in all solvents (other than molten sodium metal), consistent with the fact that H − ions do not exist in solution.
NaH is colorless, although samples generally appear grey. NaH is around 40% denser than Na (0.968 g/cm 3 ).
NaH, like LiH , KH , RbH , and CsH , adopts the NaCl crystal structure . In this motif, each Na + ion is surrounded by six H − centers in an octahedral geometry. The ionic radii of H − (146 pm in NaH) and F − (133 pm) are comparable, as judged by the Na−H and Na−F distances. [ 8 ]
A very unusual situation occurs in a compound dubbed "inverse sodium hydride", which contains H + and Na − ions. Na − is an alkalide , and this compound differs from ordinary sodium hydride in having a much higher energy content due to the net displacement of two electrons from hydrogen to sodium. A derivative of this "inverse sodium hydride" arises in the presence of the base [3 6 ]adamanzane . This molecule irreversibly encapsulates the H + and shields it from interaction with the alkalide Na − . [ 9 ] Theoretical work has suggested that even an unprotected protonated tertiary amine complexed with the sodium alkalide might be metastable under certain solvent conditions, though the barrier to reaction would be small and finding a suitable solvent might be difficult. [ 10 ]
Industrially, NaH is prepared by introducing molten sodium into mineral oil with hydrogen at atmospheric pressure and mixed vigorously at ~8000 rpm. The reaction is especially rapid at 250−300 °C.
The resultant suspension of NaH in mineral oil is often directly used, such as in the production of diborane . [ 11 ]
NaH is a base of wide scope and utility in organic chemistry. [ 12 ] As a superbase , it is capable of deprotonating a range of even weak Brønsted acids to give the corresponding sodium derivatives. Typical "easy" substrates contain O-H, N-H, S-H bonds, including alcohols , phenols , pyrazoles , and thiols .
NaH notably deprotonates carbon acids (i.e., C-H bonds) such as 1,3- dicarbonyls such as malonic esters . The resulting sodium derivatives can be alkylated. NaH is widely used to promote condensation reactions of carbonyl compounds via the Dieckmann condensation , Stobbe condensation , Darzens condensation , and Claisen condensation . Other carbon acids susceptible to deprotonation by NaH include sulfonium salts and DMSO . NaH is used to make sulfur ylides , which in turn are used to convert ketones into epoxides , as in the Johnson–Corey–Chaykovsky reaction .
NaH reduces certain main group compounds, but analogous reactivity is very rare in organic chemistry ( see below ). [ 13 ] Notably boron trifluoride reacts to give diborane and sodium fluoride : [ 14 ]
Si–Si and S–S bonds in disilanes and disulfides are also reduced.
A series of reduction reactions, including the hydrodecyanation of tertiary nitriles, reduction of imines to amines, and amides to aldehydes, can be effected by a composite reagent composed of sodium hydride and an alkali metal iodide (NaH⋅MI, M = Li, Na). [ 15 ]
Although not commercially significant sodium hydride has been proposed for hydrogen storage for use in fuel cell vehicles. In one experimental implementation, plastic pellets containing NaH are crushed in the presence of water to release the hydrogen. One challenge with this technology is the regeneration of NaH from the NaOH formed by hydrolysis. [ 16 ]
Sodium hydride is sold as a mixture of 60% sodium hydride (w/w) in mineral oil . Such a dispersion is safer to handle and weigh than pure NaH. The compound is often used in this form but the pure grey solid can be prepared by rinsing the commercial product with pentane or tetrahydrofuran, with care being taken because the waste solvent will contain traces of NaH and can ignite in air. Reactions involving NaH usually require air-free techniques .
NaH can ignite spontaneously in air . It also reacts vigorously with water or humid air to release hydrogen , which is very flammable, and sodium hydroxide (NaOH), a quite corrosive base . In practice, most sodium hydride is sold as a dispersion in mineral oil , which can be safely handled in air. [ 17 ] Although sodium hydride is widely used in DMSO , DMF or DMAc for SN2 type reactions there have been many cases of fires and/or explosions from such mixtures. [ 18 ] [ 19 ] | https://en.wikipedia.org/wiki/NaH |
Monosodium phosphate ( MSP ), also known as monobasic sodium phosphate and sodium dihydrogen phosphate , is an inorganic compound with the chemical formula Na H 2 P O 4 . It is a sodium salt of phosphoric acid . It consists of sodium cations ( Na + ) and dihydrogen phosphate anions ( H 2 PO − 4 ). One of many sodium phosphates , it is a common industrial chemical . The salt exists in an anhydrous form, as well as monohydrate and dihydrate ( NaH 2 PO 4 ·H 2 O and NaH 2 PO 4 ·2H 2 O respectively). [ 1 ]
The salt is obtained by partial neutralization of phosphoric acid .
The p K a of monosodium phosphate is 6.8-7.2 (depending on the physicochemical characteristics during p K a determination). [ 2 ]
Heating this salt above 169 °C gives disodium pyrophosphate :
When heated at 550 °C, anhydrous trisodium trimetaphosphate is formed: [ 3 ]
Phosphates are often used in foods and in water treatment. The pH of such formulations is adjusted by mixtures of various sodium phosphates , such as this salt. [ 1 ] It is added in animal feed for its nutritional value. [ 1 ] | https://en.wikipedia.org/wiki/NaH2PO4 |
Sodium formate , HCOONa, is the sodium salt of formic acid , HCOOH. It usually appears as a white deliquescent powder.
For commercial use, sodium formate is produced by absorbing carbon monoxide under pressure in solid sodium hydroxide at 130 °C and 6-8 bar pressure: [ 1 ]
Because of the low-cost and large-scale availability of formic acid by carbonylation of methanol and hydrolysis of the resulting methyl formate, sodium formate is usually prepared by neutralizing formic acid with sodium hydroxide . Sodium formate is also unavoidably formed as a by-product in the final step of the pentaerythritol synthesis and in the crossed Cannizzaro reaction of formaldehyde with the aldol reaction product trimethylol acetaldehyde [3-hydroxy-2,2-bis(hydroxymethyl)propanal]. [ 2 ]
In the laboratory, sodium formate can be prepared by neutralizing formic acid with sodium carbonate . It can also be obtained by reacting chloroform with an alcoholic solution of sodium hydroxide .
or by reacting sodium hydroxide with chloral hydrate .
The latter method is, in general, preferred to the former because the low aqueous solubility of CHCl 3 makes it easier to separate out from the sodium formate solution, by fractional crystallization , than the soluble NaCl would be.
Sodium formate crystallizes in a monoclinic crystal system with the lattice parameters a = 6,19 Å, b = 6,72 Å, c = 6,49 Å and β = 121,7°. [ 3 ]
On heating, sodium formate decomposes to form sodium oxalate and hydrogen. [ 4 ] The resulting sodium oxalate can be converted by further heating to sodium carbonate upon release of carbon monoxide: [ 5 ] [ 4 ]
As a salt of a weak acid ( formic acid ) and a strong base ( sodium hydroxide ) sodium formate reacts in aqueous solutions basic:
A solution of formic acid and sodium formate can thus be used as a buffer solution.
Sodium formate is slightly water-hazardous and inhibits some species of bacteria but is degraded by others.
Sodium formate is used in several fabric dyeing and printing processes. It is also used as a buffering agent for strong mineral acids to increase their pH , as a food additive (E237), and as a de-icing agent.
In structural biology , sodium formate can be used as a cryoprotectant for X-ray diffraction experiments on protein crystals, [ 6 ] which are typically conducted at a temperature of 100 K to reduce the effects of radiation damage .
Sodium formate plays a role in the synthesis of formic acid , it is converted by sulfuric acid via the following reaction equation:
The urticating hair of stinging nettles contain sodium formate as well as formic acid.
Solid sodium formate is used as a non-corrosive agent at airports for de-icing of runways in mix with corrosion inhibitors and other additives, which rapidly penetrate solid snow and ice layers, detach them from the asphalt or concrete and melt the ice rapidly. Sodium formate was also used as a road deicer in the city of Ottawa from 1987 to 1988. [ 7 ]
The high freezing point depression e.g. in comparison to the still frequently used urea (which is effective but problematic due to eutrophication ) effectively prevents the re-icing, even at temperatures below −15 °C. The thawing effect of the solid sodium formate can even be increased by moistening with aqueous potassium formate or potassium acetate solutions. The degradability of sodium formate is particularly advantageous with a chemical oxygen demand (COD) of 211 mg O 2 /g compared with the de-icing agents sodium acetate (740 mg O 2 /g) and urea with (> 2,000 mg O 2 /g). [ 8 ]
Saturated sodium formate solutions (as well as mixtures of other alkali metal formates such as potassium and cesium formate) are used as important drilling and stabilizing aids in gas and oil exploration because of their relatively high density. By mixing the corresponding saturated alkali metal formate solutions any densities between 1,0 and 2,3 g/cm 3 can be set. The saturated solutions are biocidal and long-term stable against microbial degradation. Diluted, on the other hand, they are fast and completely biodegradable. As alkali metal formates as drilling aids make it unnecessary to add solid fillers to increase the density (such as barytes ) and the formate solutions can be recovered and recycled at the drilling site, formates represent an important advance in exploration technology. [ 9 ] | https://en.wikipedia.org/wiki/NaHCO2 |
Sodium bicarbonate ( IUPAC name : sodium hydrogencarbonate [ 10 ] ), commonly known as baking soda or bicarbonate of soda (or simply “ bicarb ” especially in the UK) is a chemical compound with the formula NaHCO 3 . It is a salt composed of a sodium cation ( Na + ) and a bicarbonate anion ( HCO − 3 ). Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda ( sodium carbonate ). The natural mineral form is nahcolite , although it is more commonly found as a component of the mineral trona . [ 11 ]
As it has long been known and widely used, the salt has many different names such as baking soda, bread soda, cooking soda, brewing soda and bicarbonate of soda and can often be found near baking powder in stores. The term baking soda is more common in the United States, while bicarbonate of soda is more common in Australia, the United Kingdom, and New Zealand. [ 12 ] Abbreviated colloquial forms such as sodium bicarb , bicarb soda , bicarbonate , and bicarb are common. [ 13 ]
The prefix bi- in "bicarbonate" comes from an outdated naming system predating molecular knowledge. It is based on the observation that there is twice as much carbonate ( CO 2− 3 ) per sodium in sodium bicarbonate (NaHCO 3 ) as there is in sodium carbonate (Na 2 CO 3 ). [ 14 ] The modern chemical formulas of these compounds now express their precise chemical compositions which were unknown when the name bi-carbonate of potash was coined (see also: bicarbonate ).
In cooking, baking soda is primarily used in baking as a leavening agent . When it reacts with acid or is heated, carbon dioxide is released, which causes expansion of the batter and forms the characteristic texture and grain in cakes, quick breads , soda bread , and other baked and fried foods. When an acid is used, the acid–base reaction can be generically represented as follows: [ 15 ]
Acidic materials that induce this reaction include hydrogen phosphates , cream of tartar , lemon juice, yogurt , buttermilk , cocoa , and vinegar . Baking soda may be used together with sourdough , which is acidic, making a lighter product with a less acidic taste. [ 16 ] Since the reaction occurs slowly at room temperature, mixtures (cake batter, etc.) can be allowed to stand without rising until they are heated in the oven. [ citation needed ]
Heat can also by itself cause sodium bicarbonate to act as a raising agent in baking because of thermal decomposition , releasing carbon dioxide at temperatures above 80 °C (180 °F), as follows: [ 17 ]
When used this way on its own, without the presence of an acidic component (whether in the batter or by the use of a baking powder containing acid), only half the available CO 2 is released (one CO 2 molecule is formed for every two equivalents of NaHCO 3 ). Additionally, in the absence of acid, thermal decomposition of sodium bicarbonate also produces sodium carbonate , which is strongly alkaline and gives the baked product a bitter, soapy taste and a yellow color.
Baking powder , also sold for cooking, contains around 30% of bicarbonate, and various acidic ingredients that are activated by the addition of water, without the need for additional acids in the cooking medium. [ 18 ] [ 19 ] [ 20 ] Many forms of baking powder contain sodium bicarbonate combined with calcium acid phosphate , sodium aluminium phosphate , or cream of tartar . [ 21 ] Baking soda is alkaline; the acid used in baking powder avoids a metallic taste when the chemical change during baking creates sodium carbonate. [ 22 ]
It is often used in conjunction with other bottled water food additives to add taste. [ 23 ] Its European Union E number is E500. [ 24 ]
Sodium bicarbonate is one of the main components of the common "black snake" firework . The effect is caused by the thermal decomposition, which produces carbon dioxide gas to produce a long snake-like ash as a combustion product of the other main component, sucrose . [ 25 ] Sodium bicarbonate also delays combustion reactions through the release of carbon dioxide and water, both of which are flame retardants, when heated.
It has weak disinfectant properties [ 26 ] [ 27 ] and it may be an effective fungicide against some organisms. [ 28 ] As baking soda will absorb musty smells, it has become a reliable method for used booksellers when making books less malodorous. [ 29 ]
Sodium bicarbonate can be used to extinguish small grease or electrical fires by being thrown over the fire, as heating of sodium bicarbonate releases carbon dioxide. [ 30 ] However, it should not be applied to fires in deep fryers ; the sudden release of gas may cause the grease to splatter. [ 30 ] Sodium bicarbonate is used in BC dry chemical fire extinguishers as an alternative to the more corrosive monoammonium phosphate in ABC extinguishers. The alkaline nature of sodium bicarbonate makes it the only dry chemical agent, besides Purple-K , that was used in large-scale fire suppression systems installed in commercial kitchens. [ 31 ]
Sodium bicarbonate has several fire-extinguishing mechanisms that act simultaneously. It decomposes into water and carbon dioxide when heated, an endothermic reaction that deprives the fire of heat. In addition, it forms intermediates that can scavenge the free radicals which are responsible for the propagation of fire . [ 32 ] With grease fires specifically, it also has a mild saponification effect, producing a soapy foam that can help smother the fire. [ 31 ]
Sodium bicarbonate reacts spontaneously with acids, releasing CO 2 gas as a reaction product. It is commonly used to neutralize unwanted acid solutions or acid spills in chemical laboratories. [ 33 ] It is not appropriate to use sodium bicarbonate to neutralize base [ 34 ] even though it is amphoteric , reacting with both acids and bases. [ 35 ]
Sodium bicarbonate is taken as a sports supplement to improve muscular endurance. [ 36 ] Studies conducted mostly in males have shown that sodium bicarbonate is most effective in enhancing performance in short-term, high-intensity activities. [ 37 ]
Sodium bicarbonate can prevent the growth of fungi when applied on leaves, although it will not kill the fungus. Excessive amounts of sodium bicarbonate can cause discolouration of fruits (two percent solution) and chlorosis (one percent solution). [ 38 ] Sodium bicarbonate is also commonly used as a free choice dietary supplement in sheep to help prevent bloat.
Sodium bicarbonate mixed with water can be used as an antacid to treat acid indigestion and heartburn . [ 39 ] [ 40 ] Its reaction with stomach acid produces salt , water, and carbon dioxide :
A mixture of sodium bicarbonate and polyethylene glycol such as PegLyte, [ 41 ] dissolved in water and taken orally, is an effective gastrointestinal lavage preparation and laxative prior to gastrointestinal surgery, gastroscopy , etc. [ citation needed ]
Intravenous sodium bicarbonate in an aqueous solution is sometimes used for cases of acidosis , or when insufficient sodium or bicarbonate ions are in the blood. [ 42 ] In cases of respiratory acidosis, the infused bicarbonate ion drives the carbonic acid/bicarbonate buffer of plasma to the left, and thus raises the pH. For this reason, sodium bicarbonate is used in medically supervised cardiopulmonary resuscitation . Infusion of bicarbonate is indicated only when the blood pH is markedly low (< 7.1–7.0). [ 43 ]
HCO 3 − is used for treatment of hyperkalemia , as it will drive K + back into cells during periods of acidosis. [ 44 ] Since sodium bicarbonate can cause alkalosis , it is sometimes used to treat aspirin overdoses. Aspirin requires an acidic environment for proper absorption, and a basic environment will diminish aspirin absorption in cases of overdose. [ 45 ] Sodium bicarbonate has also been used in the treatment of tricyclic antidepressant overdose . [ 46 ] It can also be applied topically as a paste, with three parts baking soda to one part water, to relieve some kinds of insect bites and stings (as well as accompanying swelling). [ 47 ]
Some alternative practitioners, such as Tullio Simoncini , have promoted baking soda as a cancer cure, which the American Cancer Society has warned against due to both its unproven effectiveness and potential danger in use. [ 48 ] Edzard Ernst has called the promotion of sodium bicarbonate as a cancer cure "one of the more sickening alternative cancer scams I have seen for a long time". [ 49 ]
Sodium bicarbonate can be added to local anaesthetics , to speed up the onset of their effects and make their injection less painful. [ 50 ] It is also a component of Moffett's solution , used in nasal surgery. [ 51 ]
It has been proposed that acidic diets weaken bones. [ 52 ] One systematic meta-analysis of the research shows no such effect. [ 53 ] Another also finds that there is no evidence that alkaline diets improve bone health, but suggests that there "may be some value" to alkaline diets for other reasons. [ 54 ]
Antacid (such as baking soda) solutions have been prepared and used by protesters to alleviate the effects of exposure to tear gas during protests. [ failed verification ] [ 55 ]
Similarly to its use in baking, sodium bicarbonate is used together with a mild acid such as tartaric acid as the excipient in effervescent tablets: when such a tablet is dropped in a glass of water, the carbonate leaves the reaction medium as carbon dioxide gas (HCO 3 − + H + → H 2 O + CO 2 ↑ or, more precisely, HCO 3 − + H 3 O + → 2 H 2 O + CO 2 ↑). This makes the tablet disintegrate, leaving the medication suspended and/or dissolved in the water together with the resulting salt (in this example, sodium tartrate ). [ 56 ]
Sodium bicarbonate is also used as an ingredient in some mouthwashes. It has anticaries and abrasive properties. [ 57 ] It works as a mechanical cleanser on the teeth and gums, neutralizes the production of acid in the mouth, and also acts as an antiseptic to help prevent infections. [ 58 ] [ 59 ] Sodium bicarbonate in combination with other ingredients can be used to make a dry or wet deodorant . [ 60 ] [ 61 ] Sodium bicarbonate may be used as a buffering agent , combined with table salt, when creating a solution for nasal irrigation . [ 62 ]
It is used in eye hygiene to treat blepharitis . This is done by adding a teaspoon of sodium bicarbonate to cool water that was recently boiled followed by gentle scrubbing of the eyelash base with a cotton swab dipped in the solution. [ 63 ] [ 64 ]
Sodium bicarbonate is used as a cattle feed supplement, in particular as a buffering agent for the rumen . [ 65 ]
Sodium bicarbonate is used in a process to remove paint and corrosion called sodablasting . As a blasting medium, sodium bicarbonate is used to remove surface contamination from softer and less resilient substrates such as aluminium, copper, or timber that could be damaged by silica sand abrasive media. [ 66 ]
A manufacturer recommends a paste made from baking soda with minimal water as a gentle scouring powder. [ 30 ] Such a paste can be useful in removing surface rust because the rust forms a water-soluble compound when in a concentrated alkaline solution. [ 67 ] Cold water should be used since hot-water solutions can corrode steel. [ 68 ] Sodium bicarbonate attacks the thin protective oxide layer that forms on aluminium, making it unsuitable for cleaning this metal. [ 69 ] A solution in warm water will remove the tarnish from silver when the silver is in contact with a piece of aluminium foil . [ 69 ] [ 70 ] Baking soda is commonly added to washing machines as a replacement for water softener and to remove odors from clothes. When diluted with warm water, it is also almost as effective in removing heavy tea and coffee stains from cups as sodium hydroxide .
During the Manhattan Project to develop the nuclear bomb in the early 1940s, the chemical toxicity of uranium was an issue. Uranium oxides were found to stick very well to cotton cloth and did not wash out with soap or laundry detergent . However, the uranium would wash out with a 2% solution of sodium bicarbonate. Clothing can become contaminated with toxic dust of depleted uranium (DU), which is very dense, hence it is used for counterweights in a civilian context and in armour-piercing projectiles. DU is not removed by normal laundering; washing with about 6 ounces (170 g) of baking soda in 2 gallons (7.5 L) of water will help wash it out. [ 71 ]
It is often claimed that baking soda is an effective odor remover [ 72 ] [ better source needed ] and recommended that an open box be kept in the refrigerator to absorb odor. [ 73 ] This idea was promoted by the leading U.S. brand of baking soda, Arm & Hammer , in an advertising campaign starting in 1972. [ 74 ] Though this campaign is considered a classic of marketing, leading within a year to more than half of American refrigerators containing a box of baking soda, [ 75 ] [ 76 ] there is little evidence that it is effective in this application. [ 77 ] [ 78 ]
An educational science experiment known as the "Baking Soda and Vinegar Volcano" uses the acid-base reaction with vinegar acid to mimic a volcanic eruption. The rapid production of CO 2 causes the liquid to foam up and overflow its container. Other ingredients such as dish soap and food coloring can be added to enhance the visual effect. [ 79 ] If this reaction is performed inside of a closed vessel (such as a bottle) with no way for gas to escape, it can cause an explosion if the pressure is high enough.
Sodium bicarbonate is an amphoteric compound. [ 35 ] Aqueous solutions are mildly alkaline due to the formation of carbonic acid and hydroxide ion: [ 35 ]
Sodium bicarbonate can sometimes be used as a mild neutralization agent and a safer alternative to strong bases like sodium hydroxide . [ 80 ] Reaction of sodium bicarbonate and an acid produces a salt and carbonic acid, which readily decomposes to carbon dioxide and water: [ 80 ]
Sodium bicarbonate reacts with acetic acid (found in vinegar), producing sodium acetate , water, and carbon dioxide :
Sodium bicarbonate reacts with bases such as sodium hydroxide to form carbonates:
At temperatures from 80–100 °C (176–212 °F), sodium bicarbonate gradually decomposes into sodium carbonate , water, and carbon dioxide. The conversion is faster at 200 °C (392 °F): [ 81 ]
Most bicarbonates undergo this dehydration reaction . Further heating converts the carbonate into the oxide (above 850 °C/1,560 °F): [ 81 ]
The generation of carbon dioxide and water partially explain the fire-extinguishing properties of NaHCO 3 , [ 31 ] although other factors like heat absorption and radical scavenging are more significant. [ 32 ]
In nature, sodium bicarbonate occurs almost exclusively as either nahcolite or trona . Trona is more common, as nahcolite is more soluble in water and the chemical equilibrium between the two minerals favors trona. [ 11 ] Significant nahcolite deposits are in the United States, Botswana and Kenya, Uganda, Turkey, and Mexico. [ 82 ] The biggest trona deposits are in the Green River basin in Wyoming. [ 83 ]
Nahcolite is sometimes found as a component of oil shale . [ 84 ]
If kept cool ( room temperature ) and dry (an airtight container is recommended to keep out moist air), sodium bicarbonate can be kept without a significant amount of decomposition for at least two or three years. [ 85 ] [ 86 ] [ 87 ] [ 88 ]
The word natron has been in use in many languages throughout modern times (in the forms of anatron , natrum and natron ) and originated (like Spanish , French and English natron as well as ' sodium ') via Arabic naṭrūn (or anatrūn ; cf. the Lower Egyptian “Natrontal” Wadi El Natrun , where a mixture of sodium carbonate and sodium hydrogen carbonate for the dehydration of mummies was used [ 89 ] ) from Greek nítron (νίτρον) (Herodotus; Attic lítron (λίτρον) ), which can be traced back to ancient Egyptian ntr . The Greek nítron (soda, saltpeter) was also used in Latin (sal) nitrum and in German Salniter (the source of Nitrogen , Nitrat etc.). [ 90 ] [ 91 ] The word saleratus , from Latin sal æratus (meaning "aerated salt"), was widely used in the 19th century for both sodium bicarbonate and potassium bicarbonate . [ 92 ]
In 1791, French chemist Nicolas Leblanc produced sodium carbonate (also known as soda ash). Pharmacist Valentin Rose the Younger is credited with the discovery of sodium bicarbonate in 1801 in Berlin. In 1846, two American bakers, John Dwight and Austin Church , established the first factory in the United States to produce baking soda from sodium carbonate and carbon dioxide . [ 93 ]
Saleratus , potassium or sodium bicarbonate, is mentioned in the novel Captains Courageous by Rudyard Kipling as being used extensively in the 1800s in commercial fishing to prevent freshly caught fish from spoiling. [ 94 ]
In 1919, US Senator Lee Overman declared that bicarbonate of soda could cure the Spanish flu . In the midst of the debate on 26 January 1919, he interrupted the discussion to announce the discovery of a cure. "I want to say, for the benefit of those who are making this investigation," he reported, "that I was told by a judge of a superior court in the mountain country of North Carolina they have discovered a remedy for this disease." The purported cure implied a critique of modern science and an appreciation for the simple wisdom of simple people. "They say that common baking soda will cure the disease," he continued, "that they have cured it with it, that they have no deaths up there at all; they use common baking soda, which cures the disease." [ 95 ]
Sodium bicarbonate is produced industrially from sodium carbonate : [ 96 ]
It is produced on the scale of about 100,000 tonnes/year (as of 2001) [ dubious – discuss ] [ 97 ] with a worldwide production capacity of 2.4 million tonnes per year (as of 2002). [ 98 ] Commercial quantities of baking soda are also produced by a similar method: soda ash, mined in the form of the ore trona , is dissolved in water and treated with carbon dioxide. Sodium bicarbonate precipitates as a solid from this solution. [ citation needed ]
Regarding the Solvay process , sodium bicarbonate is an intermediate in the reaction of sodium chloride , ammonia , and carbon dioxide . The product however shows low purity (75pc). [ citation needed ]
Although of no practical value, NaHCO 3 may be obtained by the reaction of carbon dioxide with an aqueous solution of sodium hydroxide: [ citation needed ]
Naturally occurring deposits of nahcolite (NaHCO 3 ) are found in the Eocene -age (55.8–33.9 Mya) Green River Formation , Piceance Basin in Colorado . Nahcolite was deposited as beds during periods of high evaporation in the basin. It is commercially mined using common underground mining techniques such as bore, drum, and longwall mining in a fashion very similar to coal mining. [ citation needed ]
It is also produced by solution mining, pumping heated water through nahcolite beds and crystallizing the dissolved nahcolite through a cooling crystallization process.
Since nahcolite is sometimes found in shale , it can be produced as a co-product of shale oil extraction , where it is recovered by solution mining. [ 84 ]
Sodium bicarbonate, as "bicarbonate of soda", was a frequent source of punch lines for Groucho Marx in Marx Brothers movies. In Duck Soup , Marx plays the leader of a nation at war. In one scene, he receives a message from the battlefield that his general is reporting a gas attack, and Groucho tells his aide: "Tell him to take a teaspoonful of bicarbonate of soda and a half a glass of water." [ 99 ] In A Night at the Opera , Groucho's character addresses the opening night crowd at an opera by saying of the lead tenor: "Signor Lassparri comes from a very famous family. His mother was a well-known bass singer. His father was the first man to stuff spaghetti with bicarbonate of soda, thus causing and curing indigestion at the same time." [ 100 ]
In the Joseph L. Mankewicz classic All About Eve , the Max Fabian character ( Gregory Ratoff ) has an extended scene with Margo Channing ( Bette Davis ) in which, suffering from heartburn, he requests and then drinks bicarbonate of soda, eliciting a prominent burp. Channing promises to always keep a box of bicarb with Max's name on it. | https://en.wikipedia.org/wiki/NaHCO3 |
Sodium bisulfite (or sodium bisulphite , sodium hydrogen sulfite ) is a chemical mixture with the approximate chemical formula NaHSO 3 . Sodium bisulfite is not a real compound, [ 2 ] but a mixture of salts that dissolve in water to give solutions composed of sodium and bisulfite ions. It appears in form of white or yellowish-white crystals with an odor of sulfur dioxide . Sodium bisulfite is used in a variety industries such as a food additive with E number E222 in the food industry. It is a reducing agent in the cosmetic and in the bleaching applications. [ 3 ] [ 4 ] [ 5 ]
Sodium bisulfite solutions can be prepared by treating a solution of suitable base, such as sodium hydroxide or sodium bicarbonate with sulfur dioxide .
Attempts to crystallize the product yield sodium metabisulfite (also called sodium disulfite ), Na 2 S 2 O 5 . [ 6 ]
Upon dissolution of the metabisulfite in water, bisulfite is regenerated:
Sodium bisulfite is formed during the Wellman-Lord process . [ 7 ]
Sodium bisulfite functions as a hair-waving/straightening agent. [ 8 ] As of 1998, sodium bisulfite was used in 58 cosmetic products including hair conditioners, moisturizers, and hair dyes. [ 9 ]
Sodium bisulfite is used to prevent discoloration, bleach food starches, and delay spoilage of the product. In the US, EPA , FDA , and American Conference of Governmental Industrial Hygienists established a working place threshold limit value for sulfur dioxide of 2ppm averaged over 8 hours, and a 3-hour level of 5ppm. Even with this threshold established, the FDA recognized sodium bisulfite as "generally recognized as safe" compound. [ 3 ]
Sulfites in food can be assayed by the Monier-Williams type procedure, [ 10 ] HPLC after extraction, and Flow Injection analysis. [ 5 ]
Sodium bisulfite is used as an antichlor in the textile industry. [ 3 ] [ 4 ] Antichlors are very useful in the textile industry because bleaching of compounds using chlorine is a standard practice.
The International Agency for Research on Cancer concluded that there was inadequate evidence that sodium bisulfite was carcinogenic . [ 3 ] Under specific conditions such as acidity and concentration level, sodium bisulfite was able to cause negative alterations to the genome such as catalyzing transamination , and to induce sister-chromatid exchanges suggesting possible genotoxicity . [ 11 ] In a study using Osbourne-Mendel strain rats, it was concluded that oral toxicity was not significant if the consumed concentration was less than 0.1% (615 ppm as SO 2 ). [ 12 ] A study by Servalli, Lear, and Cottree in 1984 found that sodium bisulfite did not produce membrane fusion in hepatic and murine glial cells and human fibroblasts , so there is no oral toxicity. These clinical studies concluded that sodium bisulfite was safe to use in cosmetic formulations. [ 3 ]
The concentrations of sodium bisulfite that could be dangerous are well beyond the concentrations discussed in the cosmetic and food industry.. [ 4 ] [ 13 ]
The World Health Organization Expert Committee on Food Additives concluded that 0-0.7mg of sulfur dioxide equivalent/kg of body weight per day will cause no harm to an individual consuming this compound as a food additive. Sulfites exhibit no genotoxicity and carcinogenicity. [ 5 ] | https://en.wikipedia.org/wiki/NaHSO3 |
Sodium bisulfate , also known as sodium hydrogen sulfate , [ a ] is the sodium salt of the bisulfate anion , with the molecular formula NaHSO 4 . Sodium bisulfate is an acid salt formed by partial neutralization of sulfuric acid by an equivalent of sodium base, typically in the form of either sodium hydroxide (lye) or sodium chloride (table salt). It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic . Solutions of sodium bisulfate are acidic, with a 1M solution having a pH of slightly below 1.
Sodium bisulfate is produced as an intermediate in the Mannheim process , an industrial process involving the reaction of sodium chloride and sulfuric acid : [ 1 ]
The process for the formation of sodium bisulfate is highly exothermic. The liquid sodium bisulfate is sprayed and cooled so that it forms a solid bead. The hydrogen chloride gas is dissolved in water to produce hydrochloric acid as a useful coproduct of the reaction.
Sodium bisulfate can be generated as a byproduct of the production of many other mineral acids via the reaction of their sodium salts with an excess of sulfuric acid :
The acids HX produced have a lower boiling point than the reactants and are separated from the reaction mixture by distillation.
Hydrated sodium bisulfate dehydrates at 58 °C (136 °F) at which point it separates from the water molecule attached to it. Once cooled again, it is freshly hygroscopic. Heating sodium bisulfate to 280 °C (536 °F) produces sodium pyrosulfate , another colorless salt: [ 1 ]
Sodium bisulfate is used primarily to lower pH. It is also used in metal finishing, cleaning products , [ 2 ] and to lower the pH of water for effective chlorination in swimming pools and hot tubs. [ 3 ] Sodium bisulfate is also AAFCO approved as a general-use feed additive, including use in poultry feed [ 4 ] and companion animal food. [ 5 ] It is used as a urine acidifier to reduce urinary stones in cats. [ 6 ]
It is highly toxic to certain echinoderms , but fairly harmless to most other life forms; so it is used in controlling outbreaks of crown-of-thorns starfish .
Sodium bisulfate was the primary active ingredient in the toilet bowl cleaners Vanish and Sani-Flush , both now discontinued. [ 7 ]
In the textiles industry, it is sometimes applied to velvet cloth made with a silk backing and a pile of cellulose-based fiber (rayon, cotton, hemp, etc.) to create "burnout velvet": the sodium bisulfate, when applied to such a fabric and heated, causes the cellulose-based fibers to become brittle and flake away, leaving burned-out areas in the finished material, usually in attractive patterns. [ 8 ]
Sodium bisulfate is the active ingredient in some granular poultry litter treatments used to control ammonia. [ 9 ] Sodium bisulfate has also been shown to significantly reduce the concentration of Campylobacter and Salmonella in chicken houses. [ 10 ]
Sodium bisulfate is sometimes used as the active ingredient in flocculant tablets, a step in soil and water quality test kits. [ 11 ]
Sodium bisulfate is used as a food additive to leaven cake mixes (make them rise) [ 12 ] as well as being used in meat and poultry processing and most recently in browning prevention of fresh-cut produce. [ 13 ] Sodium bisulfate is considered generally recognized as safe (GRAS) by the FDA and has been named to the EPA Safer Choice [ 14 ] Safer Chemicals Ingredients List. The food-grade product also meets the requirements set out in the Food Chemicals Codex . It is denoted by E number E514ii in the EU and is also approved for use in Australia, New Zealand, Canada, and Mexico. [ 15 ] where it is listed as additive 514. Food grade sodium bisulfate is used in a variety of food products, including beverages, dressings, sauces, and fillings. It has many synonyms including [ 16 ] bisulfate of soda, sodium acid sulfate, mono sodium hydrogen sulfate, sodium hydrogen sulfate, sodium hydrosulfate, and sulfuric acid sodium salt (1:1).
Sodium bisulfate lowers the pH without creating a sour taste, and has been used in the place of citric, malic, or phosphoric acids that are commercially available, [ 9 ] and it can also be used as an anti-browning agent. [ 17 ]
The "bi" refers to the presence of the hydrogen. | https://en.wikipedia.org/wiki/NaHSO4 |
Sodium iodide ( chemical formula NaI ) is an ionic compound formed from the chemical reaction of sodium metal and iodine . Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na + ) and iodide anions (I − ) in a crystal lattice . It is used mainly as a nutritional supplement and in organic chemistry . It is produced industrially as the salt formed when acidic iodides react with sodium hydroxide . [ 11 ] It is a chaotropic salt .
Sodium iodide, as well as potassium iodide , is commonly used to treat and prevent iodine deficiency . Iodized table salt contains 10 ppm iodide . [ 11 ]
Sodium iodide is used for conversion of alkyl chlorides into alkyl iodides . This method, the Finkelstein reaction , [ 13 ] relies on the insolubility of sodium chloride in acetone to drive the reaction: [ 14 ]
Some radioactive iodide salts of sodium, including Na 125 I and Na 131 I , have radiopharmaceutical uses for thyroid cancer and hyperthyroidism or as radioactive tracer in imaging (see Isotopes of iodine > Radioiodines I-123, I-124, I-125, and I-131 in medicine and biology ).
Sodium iodide activated with thallium , NaI(Tl), when subjected to ionizing radiation , emits photons (i.e., scintillate ) and is used in scintillation detectors , traditionally in nuclear medicine , geophysics , nuclear physics , and environmental measurements. NaI(Tl) is the most widely used scintillation material. The crystals are usually coupled with a photomultiplier tube , in a hermetically sealed assembly, as sodium iodide is hygroscopic . Fine-tuning of some parameters (i.e., radiation hardness , afterglow , transparency ) can be achieved by varying the conditions of the crystal growth . Crystals with a higher level of doping are used in X-ray detectors with high spectrometric quality. Sodium iodide can be used both as single crystals and as polycrystals for this purpose. The wavelength of maximum emission is 415 nm. [ 15 ]
António Egas Moniz searched for a radiocontrast agent for cerebral angiography . [ 16 ] After experiments on rabbits and dogs he settled upon sodium iodide as the best medium. [ 16 ]
Sodium iodide exhibits high solubility in some organic solvents, unlike sodium chloride or even bromide:
Iodides (including sodium iodide) are detectably oxidized by atmospheric oxygen (O 2 ) to molecular iodine (I 2 ). I 2 and I − complex to form the triiodide complex, which has a yellow color, unlike the white color of sodium iodide. Water accelerates the oxidation process, and iodide can also produce I 2 by photooxidation, therefore for maximum stability sodium iodide should be stored under dark, low temperature, low humidity conditions. | https://en.wikipedia.org/wiki/NaI |
Sodium hypoiodite is an inorganic chemical used as an oxidant in various organic chemical reactions. It causes iodination of nitrogen atoms, such 1 H -benzotriazole to give 1-iodo-1 H -benzotriazole and an imine to give the analogous iodoimine. [ 1 ] It oxidatively cleaves methyl ketones to give iodoform . [ 2 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NaIO |
Sodium iodate ( Na I O 3 ) is the sodium salt of iodic acid . Sodium iodate is an oxidizing agent . It has several uses.
It can be prepared by reacting a sodium-containing base such as sodium hydroxide with iodic acid , for example:
It can also be prepared by adding iodine to a hot, concentrated solution of sodium hydroxide or sodium carbonate :
Sodium iodate can be oxidized to sodium periodate in water solutions by hypochlorites or other strong oxidizing agents:
The main use of sodium iodate in everyday life is in iodised salt . The other compounds which are used in iodised table salt are potassium iodate , potassium iodide , and sodium iodide . Sodium iodate comprises 15 to 50 mg per kilogram of applicable salt.
Sodium iodate is also used as a dough conditioner to strengthen the dough .
Iodates combined with organic compounds form an explosive mixture. [ citation needed ] | https://en.wikipedia.org/wiki/NaIO3 |
Sodium periodate is an inorganic salt, composed of a sodium cation and the periodate anion . It may also be regarded as the sodium salt of periodic acid . Like many periodates, it can exist in two different forms: sodium meta periodate (formula NaIO 4 ) and sodium ortho periodate (normally Na 2 H 3 IO 6 , but sometimes the fully reacted salt Na 5 IO 6 ). Both salts are useful oxidising agents. [ 2 ]
Classically, periodate was produced in the form of sodium hydrogen periodate ( Na 3 H 2 IO 6 ). [ 3 ] This commercially available, but can also be produced by the oxidation of iodates with chlorine and sodium hydroxide . [ 3 ] [ 4 ] Or, similarly, from iodides by oxidation with bromine and sodium hydroxide:
Modern industrial scale production involves the electrochemical oxidation of iodates, on a lead dioxide ( PbO 2 ) anode, with the following standard electrode potential :
Sodium metaperiodate can be prepared by the dehydration of sodium hydrogen periodate with nitric acid .
Sodium metaperiodate (NaIO 4 ) forms tetragonal crystals ( space group I 4 1 / a ) consisting of slightly distorted IO − 4 ions with average I–O bond distances of 1.775 Å; the Na + ions are surrounded by 8 oxygen atoms at distances of 2.54 and 2.60 Å. [ 6 ]
Sodium hydrogen periodate (Na 2 H 3 IO 6 ) forms orthorhombic crystals (space group Pnnm). Iodine and sodium atoms are both surrounded by an octahedral arrangement of 6 oxygen atoms; however the NaO 6 octahedron is strongly distorted. IO 6 and NaO 6 groups are linked via common vertices and edges. [ 7 ]
Powder diffraction indicates that Na 5 IO 6 crystallises in the monoclinic system (space group C2/m). [ 8 ]
Sodium periodate can be used in solution to open saccharide rings between vicinal diols leaving two aldehyde groups. This process is often used in labeling saccharides with fluorescent molecules or other tags such as biotin . Because the process requires vicinal diols, periodate oxidation is often used to selectively label the 3′-ends of RNA ( ribose has vicinal diols) instead of DNA as deoxyribose does not have vicinal diols.
NaIO 4 is used in organic chemistry to cleave diols to produce two aldehydes . [ 9 ]
In 2013 the US Army announced that it would replace environmentally harmful chemicals barium nitrate and potassium perchlorate with sodium metaperiodate for use in their tracer ammunition . [ 10 ] | https://en.wikipedia.org/wiki/NaIO4 |
Sodium permanganate is the inorganic compound with the formula Na MnO 4 . It is closely related to the more commonly encountered potassium permanganate , but it is generally less desirable, because it is more expensive to produce. It is mainly available as the monohydrate . This salt absorbs water from the atmosphere and has a low melting point. Being about 15 times more soluble than KMnO 4 , sodium permanganate finds some applications where very high concentrations of MnO 4 − are sought.
Sodium permanganate cannot be prepared analogously to the route to KMnO 4 because the required intermediate manganate salt, Na 2 MnO 4 , does not form. Thus less direct routes are used including conversion from KMnO 4 . [ 1 ]
Sodium permanganate behaves similarly to potassium permanganate . It dissolves readily in water to give deep purple solutions, evaporation of which gives prismatic purple-black glistening crystals of the monohydrate NaMnO 4 ·H 2 O. The potassium salt does not form a hydrate . Because of its hygroscopic nature, it is less useful in analytical chemistry than its potassium counterpart.
It can be prepared by the reaction of manganese dioxide with sodium hypochlorite:
Because of its high solubility, its aqueous solutions are used as a drilled hole debris remover and etchant in printed circuitry , with a limited utility though. [ 1 ] It is gaining popularity in water treatment for taste, odor, and zebra mussel control. [ 2 ] The V-2 rocket used it in combination with hydrogen peroxide to drive a steam turbopump . [ 3 ]
As an oxidizer, sodium permanganate is used in environmental remediation of soil and groundwater contaminated with chlorinated solvents using the remediation technology in situ chemical oxidation, also referred to as ISCO. [ 4 ] | https://en.wikipedia.org/wiki/NaMnO4 |
Natrophilite is a mineral with the chemical formula Na Mn P O 4 . In a pure form it has a yellow coloration. Its crystals are orthorhombic to dipyramidal. It is transparent to translucent . It is not radioactive . Natrophilite is rated 4.5 to 5 on the Mohs Scale .
This article about a specific phosphate mineral is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NaMnPO4 |
In computing , NaN ( / n æ n / ), standing for Not a Number , is a particular value of a numeric data type (often a floating-point number ) which is undefined as a number, such as the result of 0/0 . Systematic use of NaNs was introduced by the IEEE 754 floating-point standard in 1985, along with the representation of other non-finite quantities such as infinities .
In mathematics , the result of 0 / 0 is typically not defined as a number [ a ] and may therefore be represented by NaN in computing systems.
The square root of a negative number is not a real number , and is therefore also represented by NaN in compliant computing systems. NaNs may also be used to represent missing values in computations. [ 1 ] [ 2 ]
Two separate kinds of NaNs are provided, termed quiet NaNs and signaling NaNs . Quiet NaNs are used to propagate errors resulting from invalid operations or values. Signaling NaNs can support advanced features such as mixing numerical and symbolic computation or other extensions to basic floating-point arithmetic.
In floating-point calculations, NaN is not the same as infinity , although both are typically handled as special cases in floating-point representations of real numbers as well as in floating-point operations. An invalid operation is also not the same as an arithmetic overflow (which would return an infinity or the largest finite number in magnitude) or an arithmetic underflow (which would return the smallest normal number in magnitude, a subnormal number , or zero ).
In the IEEE 754 binary interchange formats, NaNs are encoded with the exponent field filled with ones (like infinity values), and some non-zero number in the trailing significand field (to make them distinct from infinity values); this allows the definition of multiple distinct NaN values, depending on which bits are set in the trailing significand field, but also on the value of the leading sign bit (but applications are not required to provide distinct semantics for those distinct NaN values).
For example, an IEEE 754 single precision (32-bit) NaN would be encoded as
where s is the sign (most often ignored in applications) and the x sequence represents a non-zero number (the value zero encodes infinities). In practice, the most significant bit from x is used to determine the type of NaN: " quiet NaN " or " signaling NaN " (see details in Encoding ). The remaining bits encode a payload (most often ignored in applications).
Floating-point operations other than ordered comparisons normally propagate a quiet NaN ( qNaN ). Most floating-point operations on a signaling NaN ( sNaN ) signal the invalid-operation exception ; the default exception action is then the same as for qNaN operands and they produce a qNaN if producing a floating-point result.
The propagation of quiet NaNs through arithmetic operations allows errors to be detected at the end of a sequence of operations without extensive testing during intermediate stages. For example, if one starts with a NaN and adds 1 five times in a row, each addition results in a NaN, but there is no need to check each calculation because one can just note that the final result is NaN. However, depending on the language and the function, NaNs can silently be removed from a chain of calculations where one calculation in the chain would give a constant result for all other floating-point values. For example, the calculation x 0 may produce the result 1, even where x is NaN, so checking only the final result would obscure the fact that a calculation before the x 0 resulted in a NaN. In general, then, a later test for a set invalid flag is needed to detect all cases where NaNs are introduced [ 3 ] (see Function definition below for further details).
In section 6.2 of the old IEEE 754-2008 standard, there are two anomalous functions (the maxNum and minNum functions, which return the maximum and the minimum, respectively, of two operands that are expected to be numbers) that favor numbers — if just one of the operands is a NaN then the value of the other operand is returned. The IEEE 754-2019 revision has replaced these functions as they are not associative (when a signaling NaN appears in an operand). [ 4 ] [ 5 ]
Comparisons are specified by the IEEE 754 standard to take into account possible NaN operands. [ 6 ] When comparing two real numbers, or extended real numbers (as in the IEEE 754 floating-point formats), the first number may be either less than, equal to, or greater than the second number. This gives three possible relations. But when at least one operand of a comparison is NaN, this trichotomy does not apply, and a fourth relation is needed: unordered . In particular, two NaN values compare as unordered, not as equal.
As specified, the predicates associated with the <, ≤, =, ≥, > mathematical symbols (or equivalent notation in programming languages) return false on an unordered relation. So, for instance, NOT ( x < y ) is not logically equivalent to x ≥ y : on unordered, i.e. when x or y is NaN, the former returns true while the latter returns false. However, ≠ is defined as the negation of =, thus it returns true on unordered.
From these rules, comparing x with itself, x ≠ x or x = x , can be used to test whether x is NaN or non-NaN.
The comparison predicates are either signaling or non-signaling on quiet NaN operands; the signaling versions signal the invalid-operation exception for such comparisons (i.e., by default, this just sets the corresponding status flag in addition to the behavior of the non-signaling versions). The equality and inequality predicates are non-signaling. The other standard comparison predicates associated with the above mathematical symbols are all signaling if they receive a NaN operand. The standard also provides non-signaling versions of these other predicates. The predicate isNaN( x ) determines whether a value is a NaN and never signals an exception, even if x is a signaling NaN.
The IEEE floating-point standard requires that NaN ≠ NaN hold. In contrast, the 2022 private standard of posit arithmetic has a similar concept, NaR (Not a Real), where NaR = NaR holds. [ 7 ]
There are three kinds of operations that can return NaN: [ 8 ]
NaNs may also be explicitly assigned to variables, typically as a representation for missing values. Prior to the IEEE standard, programmers often used a special value (such as −99999999) to represent undefined or missing values, but there was no guarantee that they would be handled consistently or correctly. [ 1 ]
NaNs are not necessarily generated in all the above cases. If an operation can produce an exception condition and traps are not masked then the operation will cause a trap instead. [ 9 ] If an operand is a quiet NaN, and there is also no signaling NaN operand, then there is no exception condition and the result is a quiet NaN. Explicit assignments will not cause an exception even for signaling NaNs.
In general, quiet NaNs, or qNaNs, do not raise any additional exceptions, as they propagate through most operations. But the invalid-operation exception is signaled by some operations that do not return a floating-point value, such as format conversions or certain comparison operations.
Signaling NaNs, or sNaNs, are special forms of a NaN that, when consumed by most operations, should raise the invalid operation exception and then, if appropriate, be "quieted" into a qNaN that may then propagate. They were introduced in IEEE 754 . There have been several ideas for how these might be used:
When encountered, a trap handler could decode the sNaN and return an index to the computed result. In practice, this approach is faced with many complications. The treatment of the sign bit of NaNs for some simple operations (such as absolute value ) is different from that for arithmetic operations. Traps are not required by the standard. [ citation needed ]
IEEE 754-2019 recommends the operations getPayload , setPayload , and setPayloadSignaling be implemented, [ 10 ] standardizing the access to payloads to streamline application use. [ 11 ] According to the IEEE 754-2019 background document, this recommendation should be interpreted as "required for new implementations, with reservation for backward compatibility". [ 12 ]
In IEEE 754 interchange formats, NaNs are identified by specific, pre-defined bit patterns unique to NaNs. The sign bit does not matter. For the binary formats, NaNs are represented with the exponent field filled with ones (like infinity values), and some non-zero number in the trailing significand field (to make them distinct from infinity values). The original IEEE 754 standard from 1985 ( IEEE 754-1985 ) only described binary floating-point formats, and did not specify how the signaling/quiet state was to be tagged. In practice, the most significant bit of the trailing significand field determined whether a NaN is signaling or quiet. Two different implementations, with reversed meanings, resulted:
The former choice has been preferred as it allows the implementation to quiet a signaling NaN by just setting the signaling/quiet bit to 1. The reverse is not possible with the latter choice because setting the signaling/quiet bit to 0 could yield an infinity. [ 13 ]
The 2008 and 2019 revisions of the IEEE 754 standard make formal requirements and recommendations for the encoding of the signaling/quiet state.
For IEEE 754-2008 conformance, the meaning of the signaling/quiet bit in recent MIPS processors is now configurable via the NAN2008 field of the FCSR register. This support is optional in MIPS Release 3 and required in Release 5. [ 17 ]
The state of the remaining bits of the trailing significand field are not defined by the standard. These bits encode a value called the 'payload' of the NaN. For the binary formats, the encoding is unspecified. For the decimal formats, the usual encoding of unsigned integers is used. If an operation has a single NaN input and propagates it to the output, the result NaN's payload should be that of the input NaN (this is not always possible for binary formats when the signaling/quiet state is encoded by an is_signaling flag, as explained above). If there are multiple NaN inputs, the result NaN's payload should be from one of the input NaNs; the standard does not specify which.
A number of systems have the concept of a "canonical NaN", where one specific NaN value is chosen to be the only possible qNaN generated by floating-point operations not having a NaN input. The value is usually chosen to be a quiet NaN with an all-zero payload and an arbitrarily-defined sign bit.
Using a limited amount of NaN representations allows the system to use other possible NaN values for non-arithmetic purposes, the most important being "NaN-boxing", i.e. using the payload for arbitrary data. [ 24 ] (This concept of "canonical NaN" is not the same as the concept of a "canonical encoding" in IEEE 754.)
There are differences of opinion about the proper definition for the result of a numeric function that receives a quiet NaN as input. One view is that the NaN should propagate to the output of the function in all cases to propagate the indication of an error. Another view, and the one taken by the ISO C99 and IEEE 754-2008 standards in general, is that if the function has multiple arguments and the output is uniquely determined by all the non-NaN inputs (including infinity), then that value should be the result. Thus for example the value returned by hypot(±∞, qNaN) and hypot(qNaN, ±∞) is +∞.
The problem is particularly acute for the exponentiation function pow( x , y ) = x y . The expressions 0 0 , ∞ 0 and 1 ∞ are considered indeterminate forms when they occur as limits (just like ∞ × 0), and the question of whether zero to the zero power should be defined as 1 has divided opinion.
If the output is considered as undefined when a parameter is undefined, then pow(1, qNaN) should produce a qNaN. However, math libraries have typically returned 1 for pow(1, y ) for any real number y , and even when y is an infinity . Similarly, they produce 1 for pow( x , 0) even when x is 0 or an infinity. The rationale for returning the value 1 for the indeterminate forms was that the value of functions at singular points can be taken as a particular value if that value is in the limit the value [ clarification needed ] for all but a vanishingly small part of a ball around the limit value of the parameters. [ citation needed ] The 2008 version of the IEEE 754 standard says that pow(1, qNaN) and pow(qNaN, 0) should both return 1 since they return 1 whatever else is used instead of quiet NaN. Moreover, ISO C99, and later IEEE 754-2008, chose to specify pow(−1, ±∞) = 1 instead of qNaN; the reason of this choice is given in the C rationale: [ 25 ] "Generally, C99 eschews a NaN result where a numerical value is useful. ... The result of pow(−2, ∞) is +∞, because all large positive floating-point values are even integers."
To satisfy those wishing a more strict interpretation of how the power function should act, the 2008 standard defines two additional power functions: pown( x , n ) , where the exponent must be an integer, and powr( x , y ) , which returns a NaN whenever a parameter is a NaN or the exponentiation would give an indeterminate form .
Most fixed-size integer formats cannot explicitly indicate invalid data. In such a case, when converting NaN to an integer type, the IEEE 754 standard requires that the invalid-operation exception be signaled. For example in Java , such operations throw instances of java.lang.ArithmeticException . [ 26 ] In C , they lead to undefined behavior , but if annex F is supported, the operation yields an "invalid" floating-point exception (as required by the IEEE standard) and an unspecified value.
Perl 's Math::BigInt package uses "NaN" for the result of strings that do not represent valid integers. [ 27 ]
Different operating systems and programming languages may have different string representations of NaN.
Since, in practice, encoded NaNs have a sign, a quiet/signaling bit and optional 'diagnostic information' (sometimes called a payload ), these will occasionally be found in string representations of NaNs, too. Some examples are:
Not all languages admit the existence of multiple NaNs. For example, ECMAScript only uses one NaN value throughout. | https://en.wikipedia.org/wiki/NaN |
Sodium nitrite is an inorganic compound with the chemical formula Na N O 2 . It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic . From an industrial perspective, it is the most important nitrite salt. It is a precursor to a variety of organic compounds, such as pharmaceuticals, dyes, and pesticides, but it is probably best known as a food additive used in processed meats and (in some countries) in fish products. [ 4 ]
The main use of sodium nitrite is for the industrial production of organonitrogen compounds. It is a reagent for conversion of amines into diazo compounds, which are key precursors to many dyes, such as diazo dyes . Nitroso compounds are produced from nitrites. These are used in the rubber industry. [ 4 ]
It is used in a variety of metallurgical applications, for phosphatizing and detinning. [ 4 ]
Sodium nitrite is an effective corrosion inhibitor and is used as an additive in industrial greases, [ 5 ] as an aqueous solution in closed loop cooling systems, and in a molten state as a heat transfer medium. [ 6 ]
Sodium nitrite is used to speed up the curing of meat, [ 7 ] inhibit the germination of Clostridium botulinum spores, and also impart an attractive pink color. [ 8 ] [ 9 ] Nitrite reacts with the meat myoglobin to cause color changes, first converting to nitrosomyoglobin (bright red), then, on heating, to nitrosohemochrome (a pink pigment). [ 10 ]
Historically, salt has been used for the preservation of meat. The salt-preserved meat product was usually brownish-gray in color. When sodium nitrite is added with the salt, the meat develops a red, then pink color, which is associated with cured meats such as ham, bacon, hot dogs, and bologna. [ 11 ]
In the early 1900s, irregular curing was commonplace. This led to further research surrounding the use of sodium nitrite as an additive in food, standardizing the amount present in foods to minimize the amount needed while maximizing its food additive role. [ 12 ] Through this research, sodium nitrite has been found to give taste and color to the meat and inhibit lipid oxidation that leads to rancidity, with varying degrees of effectiveness for controlling growth of disease-causing microorganisms . [ 12 ] The ability of sodium nitrite to address the above-mentioned issues has led to production of meat with extended storage life and has improved desirable color and taste. According to scientists working for the meat industry, [ 13 ] nitrite has improved food safety . [ 12 ] This view is disputed in the light of the possible carcinogenic effects caused by adding nitrites to meat. [ 7 ]
Nitrite has the E number E250. Potassium nitrite (E249) is used in the same way. It is approved for usage in the European Union, [ 14 ] [ 15 ] USA, [ 16 ] and Australia and New Zealand. [ 17 ]
In meat processing, sodium nitrite is never used in a pure state but always mixed with common salt . This mixture is known as nitrited salt, curing salt or nitrited curing salt. In Europe, nitrited curing salt contains between 99.1% and 99.5% common salt and between 0.5% and 0.9% nitrite. In the US, nitrited curing salt is dosed at 6.25% [ 18 ] and must be remixed with salt before use. [ 19 ]
The appearance and taste of meat is an important component of consumer acceptance. [ 12 ] Sodium nitrite is responsible for the desirable red color (or shaded pink) of meat. [ 12 ] Very little nitrite is needed to induce this change. [ 12 ] It has been reported that as little as 2 to 14 parts per million (ppm) is needed to induce this desirable color change. [ 20 ] However, to extend the lifespan of this color change, significantly higher levels are needed. [ 20 ] The mechanism responsible for this color change is the formation of nitrosylating agents by nitrite, which has the ability to transfer nitric oxide that subsequently reacts with myoglobin to produce the cured meat color. [ 20 ] The unique taste associated with cured meat is also affected by the addition of sodium nitrite. [ 12 ] However, the mechanism underlying this change in taste is still not fully understood. [ 20 ]
In conjunction with salt and pH levels, sodium nitrite reduces the ability of Clostridium botulinum spores to grow to the point of producing toxin. [ 9 ] [ 21 ] Some dry-cured meat products are manufactured without nitrites. For example, Parma ham , which has been produced without nitrite since 1993, was reported in 2018 to have caused no cases of botulism. This is because the interior of the muscle is sterile and the surface is exposed to oxygen. [ 7 ] Other manufacture processes do not assure these conditions, and reduction of nitrite results in toxin production. [ 22 ]
Sodium nitrite has shown varying degrees of effectiveness for controlling growth of other spoilage or disease causing microorganisms. [ 12 ] Although the inhibitory mechanisms are not well known, its effectiveness depends on several factors including residual nitrite level, pH , salt concentration, reductants present and iron content. [ 20 ] The type of bacteria also affects sodium nitrite's effectiveness. [ 20 ] It is generally agreed that sodium nitrite is not effective for controlling Gram-negative enteric pathogens such as Salmonella and Escherichia coli . [ 20 ]
Other food additives (such as lactate and sorbate ) provide similar protection against bacteria, but do not provide the desired pink color. [ 23 ] [ 24 ] [ 25 ] [ 26 ]
Sodium nitrite is also able to effectively delay the development of oxidative rancidity . [ 20 ] Lipid peroxidation is considered to be a major reason for the deterioration of quality of meat products (rancidity and unappetizing flavors). [ 20 ] Sodium nitrite acts as an antioxidant in a mechanism similar to the one responsible for the coloring effect. [ 20 ] Nitrite reacts with heme proteins and metal ions, neutralizing free radicals by nitric oxide (one of its byproducts). [ 20 ] Neutralization of these free radicals terminates the cycle of lipid oxidation that leads to rancidity. [ 20 ]
Sodium nitrite is used as a medication together with sodium thiosulfate to treat cyanide poisoning . [ 29 ] It is recommended only in severe cases of cyanide poisoning and has largely been replaced by use of hydroxocobalamin , [ 30 ] a form of vitamin B12 , but given in much higher doses than needed nutritionally. [ 31 ] In those who have both cyanide poisoning and carbon monoxide poisoning sodium thiosulfate by itself is usually recommended if the facility does not have sufficient hydroxycobalamin . [ 32 ] [ 33 ] It is given by slow injection into a vein . [ 29 ]
NaNO 2 side effects are chiefly related to creation of methemoglobinemia and vasodilation. Side effects can include low blood pressure , headache , shortness of breath , loss of consciousness , and vomiting. [ 29 ] Greater care should be taken in people with underlying heart disease. [ 29 ] The patient's levels of methemoglobin should be regularly checked during treatment. [ 29 ] While not well studied during pregnancy, there is some evidence of potential harm to the baby. [ 34 ] Sodium nitrite works by creating methemoglobin, where the iron atom at the center of the heme group is in the oxidized ferric ( Fe 3+ ) state, which binds with cyanide with greater affinity than its binding to the cytochrome C oxidase , and thus removes it from blocking the metabolic function of mitochondria . [ 34 ]
Sodium nitrite came into medical use in the 1920s and 1930s. [ 35 ] [ 36 ] It is on the World Health Organization's List of Essential Medicines . [ 37 ]
Several academic publications in 2020 and 2021 have discussed the toxicity of sodium nitrite, and an apparent recent increase in suicides using sodium nitrite which had been ordered online. [ 38 ] The usage of sodium nitrite as a suicide method has been heavily discussed on suicide forums, primarily Sanctioned Suicide . [ 39 ]
Sodium nitrite was also the focal-point of the McCarthy et al. v Amazon lawsuit alleging that Amazon knowingly assisted in the deaths of healthy children by selling them "suicide kits" as Amazon's " frequently bought together " feature recommended buying sodium nitrite, an antiemetic , and a suicide instruction book together. [ 40 ] This lawsuit was dismissed in June 2023. [ 41 ] The online marketplace eBay has globally prohibited the sale of sodium nitrite since 2019. [ 42 ] A Canadian distributor of sodium nitrite was prosecuted in 2023 for assisting suicide. [ 43 ] [ 44 ] That same year, legislation was introduced in the United States with the aim of deeming sodium nitrite products with a sodium nitrite concentration of greater than 10% by volume to be banned consumer products under the Consumer Product Safety Act . [ 45 ]
In cases of suspected suicide involving sodium nitrite, it is critical that responding individuals administer immediate intravenous methylene blue . [ 46 ] [ 47 ] [ 48 ] Methylene blue is the antidote to the methemoglobinemia caused by intentional ingestion of sodium nitrite as a suicide agent. [ 49 ]
Sodium nitrite is toxic. [ 50 ] The LD 50 in rats is 180 mg/kg and in humans LD Lo is 71 mg/kg. [ 51 ] The mechanism by which sodium nitrite causes death is methemoglobinemia . [ 52 ] The oftentimes severe methemoglobinemia found in sodium nitrite poisoning cases results in systemic hypoxia , metabolic acidosis , and cyanosis . [ 53 ] The reported [ 54 ] signs of sodium nitrite poisoning are as follows:
Symptoms of [nitrite] poisoning can vary depending on the amount and duration of the exposure. Those with very mild methemoglobinemia might not have any symptoms at all, or might appear a little pale and feel tired. Moderate-to-severe poisoning is associated with cyanosis (blueness of the skin), confusion, loss of consciousness, seizures, abnormal heart rhythms, and death.
With prompt action, sodium nitrite poisoning is reversible using an antidote, methylene blue . [ 47 ] It has been reported [ 55 ] that sodium nitrite poisoning can also be detected post-mortem:
Postmortem detection of [methemoglobinemia] is typically established via screening techniques such as scene evidence suggesting fatal consumption of a toxic salt in addition to the characteristic grey-purple lividity observed upon the body. The diagnosis can be established via postmortem blood testing demonstrating elevated methemoglobin saturation. Additionally, we have confirmed that postmortem MRI in cases of [methemoglobinemia] demonstrates a T1-bright (hyperintense) signal of the blood; both within intracardiac blood on chest MRIs and postmortem blood samples in tubes.
Death by sodium nitrite ingestion can happen at lower doses than the previously known LD Lo . [ 56 ] [ 57 ] Sodium nitrite has been used for homicide [ 58 ] [ 59 ] and suicide. [ 60 ] [ 61 ] To prevent accidental intoxication, sodium nitrite (blended with salt) sold as a food additive in the US is dyed bright pink to avoid mistaking it for plain salt or sugar. In other countries, nitrited curing salt is not dyed but is strictly regulated. [ 62 ]
Nitrites do not occur naturally in vegetables in significant quantities, [ 63 ] but deliberate fermentation of celery juice , for instance, with a naturally high level of nitrates, can produce nitrite levels sufficient for commercial meat curing. [ 64 ] Boiling vegetables does not affect nitrite levels. [ 65 ]
The presence of nitrite in animal tissue is a consequence of metabolism of nitric oxide , an important neurotransmitter. [ 66 ] Nitric oxide can be created de novo from nitric oxide synthase utilizing arginine or from ingested nitrite. [ 67 ]
Due to sodium nitrite's high level of toxicity to swine ( Sus scrofa ) it is now being developed in Australia to control feral pigs and wild boar . [ 68 ] [ 69 ] The sodium nitrite induces methemoglobinemia in swine, i.e. it reduces the amount of oxygen that is released from hemoglobin, so the animal will feel faint and pass out, and then die in a humane manner after first being rendered unconscious. [ 70 ] The Texas Parks and Wildlife Department operates a research facility at Kerr Wildlife Management Area , where they examine feral pig feeding preferences and bait tactics to administer sodium nitrite. [ 71 ]
Carcinogenicity is the ability or tendency of a chemical to induce tumors, increase their incidence or malignancy, or shorten the time of tumor occurrence. [ 72 ]
Adding nitrites to meat has been shown to generate known carcinogens such as nitrosamines ; the World Health Organization (WHO) advises that 50 g (1.8 oz) of "processed meats" a day would raise the risk of getting bowel cancer by 18% over a lifetime, and eating larger amounts raises the risk more. The World Health Organization's review of more than 400 studies concluded, in 2015, that there was sufficient evidence that "processed meats" caused cancer, particularly colon cancer; [ 7 ] the WHO's International Agency for Research on Cancer (IARC) classified "processed meats" as carcinogenic to humans ( Group 1 ); "processed meat" meaning meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation.). [ 7 ] [ 73 ]
Nitrosamines can be formed during the curing process used to preserve meats, when sodium nitrite-treated meat is cooked, and also from the reaction of nitrite with secondary amines under acidic conditions (such as occurs in the human stomach). Dietary sources of nitrosamines include US cured meats preserved with sodium nitrite as well as the dried salted fish eaten in Japan. In the 1920s, a significant change in US meat curing practices resulted in a 69% decrease in average nitrite content. This event preceded the beginning of a dramatic decline in gastric cancer mortality. [ 74 ] Around 1970, it was found that ascorbic acid (vitamin C), an antioxidant , inhibits nitrosamine formation. [ 75 ] Consequently, the addition of at least 550 ppm of ascorbic acid is required in meats manufactured in the United States. Manufacturers sometimes instead use erythorbic acid , a cheaper but equally effective isomer of ascorbic acid. Additionally, manufacturers may include α-tocopherol (vitamin E) to further inhibit nitrosamine production. α-Tocopherol, ascorbic acid, and erythorbic acid all inhibit nitrosamine production by their oxidation-reduction properties. Ascorbic acid, for example, forms dehydroascorbic acid when oxidized , which when in the presence of nitrosonium , a potent nitrosating agent formed from sodium nitrite, reduces the nitrosonium into nitric oxide. [ 76 ] The nitrosonium ion formed in acidic nitrite solutions is commonly [ 77 ] [ 78 ] mislabeled nitrous anhydride , an unstable nitrogen oxide that cannot exist in vitro. [ 79 ]
Ingesting nitrite under conditions that result in endogenous nitrosation has been classified as "probably carcinogenic to humans" by International Agency for Research on Cancer (IARC). [ 80 ] [ 81 ]
Sodium nitrite consumption has also been linked to the triggering of migraines in individuals who already experience them. [ 82 ]
One study has found a correlation between highly frequent ingestion of meats cured with pink salt and the COPD form of lung disease . [ 83 ] [ 84 ] The study's researchers suggest that the high amount of nitrites in the meats was responsible; however, the team did not prove the nitrite theory. Additionally, the study does not prove that nitrites or cured meat caused higher rates of COPD, merely a link. The researchers did adjust for many of COPD's risk factors, but they commented they cannot rule out all possible unmeasurable causes or risks for COPD. [ 85 ] [ 86 ]
Industrial production of sodium nitrite follows one of two processes, the reduction of nitrate salts, or the oxidation of lower nitrogen oxides .
One method uses molten sodium nitrate as the salt, and lead which is oxidized, while a more modern method uses scrap iron filings to reduce the nitrate. [ 4 ] [ 87 ]
A more commonly used method involves the general reaction of nitrogen oxides in alkaline aqueous solution, with the addition of a catalyst . The exact conditions depend on which nitrogen oxides are used, and what the oxidant is, as the conditions need to be carefully controlled to avoid over oxidation of the nitrogen atom. [ 4 ]
Sodium nitrite has also been produced by reduction of nitrate salts by exposure to heat, light, ionizing radiation, metals, hydrogen, and electrolytic reduction. [ 88 ]
In the laboratory, sodium nitrite can be used to destroy excess sodium azide . [ 89 ] [ 90 ]
Above 330 °C sodium nitrite decomposes (in air) to sodium oxide , nitric oxide and nitrogen dioxide . [ 91 ]
Sodium nitrite can also be used in the production of nitrous acid :
The nitrous acid then, under normal conditions, decomposes:
The resulting nitrogen dioxide hydrolyzes to a mixture of nitric and nitrous acids:
In organic synthesis isotope enriched sodium nitrite- 15 N can be used instead of normal sodium nitrite as their reactivity is nearly identical in most reactions.
The obtained products carry isotope 15 N and hence nitrogen NMR can be efficiently carried out. [ 92 ] | https://en.wikipedia.org/wiki/NaNO2 |
Sodium nitrate is the chemical compound with the formula Na N O 3 . This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile ) [ 4 ] [ 5 ] to distinguish it from ordinary saltpeter, potassium nitrate . The mineral form is also known as nitratine , nitratite or soda niter .
Sodium nitrate is a white deliquescent solid very soluble in water . It is a readily available source of the nitrate anion (NO 3 − ), which is useful in several reactions carried out on industrial scales for the production of fertilizers , pyrotechnics , smoke bombs and other explosives , glass and pottery enamels , food preservatives (esp. meats), and solid rocket propellant . It has been mined extensively for these purposes.
The first shipment of saltpeter to Europe arrived in England from Peru in 1820 or 1825, right after that country's independence from Spain, but did not find any buyers and was dumped at sea in order to avoid customs toll. [ 6 ] [ 7 ] With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons). [ 7 ] Chile fought the War of the Pacific (1879–1884) against the allies Peru and Bolivia and took over their richest deposits of saltpeter. In 1919, Ralph Walter Graystone Wyckoff determined its crystal structure using X-ray crystallography .
The largest accumulations of naturally occurring sodium nitrate are found in Chile and Peru , where nitrate salts are bound within mineral deposits called caliche ore. [ 8 ] Nitrates accumulate on land through marine-fog precipitation and sea-spray oxidation/desiccation followed by gravitational settling of airborne NaNO 3 , KNO 3 , NaCl, Na 2 SO 4 , and I, in the hot-dry desert atmosphere. [ 9 ] El Niño/La Niña extreme aridity/torrential rain cycles favor nitrates accumulation through both aridity and water solution/remobilization/transportation onto slopes and into basins; capillary solution movement forms layers of nitrates; pure nitrate forms rare veins. For more than a century, the world supply of the compound was mined almost exclusively from the Atacama desert in northern Chile until, at the turn of the 20th century, German chemists Fritz Haber and Carl Bosch developed a process for producing ammonia from the atmosphere on an industrial scale (see Haber process ). With the onset of World War I , Germany began converting ammonia from this process into a synthetic Chilean saltpeter , which was as practical as the natural compound in production of gunpowder and other munitions. By the 1940s, this conversion process resulted in a dramatic decline in demand for sodium nitrate procured from natural sources.
Chile still has the largest reserves of caliche , with active mines in such locations as Valdivia , María Elena and Pampa Blanca, and there it used to be called white gold . [ 4 ] [ 5 ] Sodium nitrate, potassium nitrate , sodium sulfate and iodine are all obtained by the processing of caliche. The former Chilean saltpeter mining communities of Humberstone and Santa Laura were declared UNESCO World Heritage sites in 2005.
Sodium nitrate is also synthesized industrially by neutralizing nitric acid with sodium carbonate or sodium bicarbonate :
or also by neutralizing it with sodium hydroxide (however, this reaction is very exothermic):
or by mixing stoichiometric amounts of ammonium nitrate and sodium hydroxide , sodium bicarbonate or sodium carbonate :
Most sodium nitrate is used in fertilizers, where it supplies a water-soluble form of nitrogen. Its use, which is mainly outside of high-income countries, is attractive since it does not alter the pH of the soil . Another major use is as a complement to ammonium nitrate in explosives. Molten sodium nitrate and its solutions with potassium nitrate have good thermal stability (up to 600 °C) and high heat capacities . These properties are suitable for thermally annealing metals and for storing thermal energy in solar applications. [ 10 ]
Sodium nitrate is also a food additive used as a preservative and color fixative in cured meats and poultry; it is listed under its INS number 251 or E number E251. It is approved for use in the EU, [ 11 ] US [ 12 ] and Australia and New Zealand. [ 13 ] Sodium nitrate should not be confused with sodium nitrite , which is also a common food additive and preservative used, for example, in deli meats.
Sodium nitrate has also been investigated as a phase-change material for thermal energy recovery, owing to its relatively high melting enthalpy of 178 J/g. [ 14 ] [ 15 ] Examples of the applications of sodium nitrate used for thermal energy storage include solar thermal power technologies and direct steam generating parabolic troughs . [ 14 ]
Sodium nitrate is used in a steel coating process in which it forms a surface of magnetite layer. [ 16 ]
Studies have shown a link between increased levels of nitrates and increased deaths from certain diseases including Alzheimer's disease , diabetes mellitus , stomach cancer , and Parkinson's disease : possibly through the damaging effect of nitrosamines on DNA; however, little has been done to control for other possible causes in the epidemiological results. [ 17 ] Nitrosamines, formed in cured meats containing sodium nitrate and nitrite, have been linked to gastric cancer and esophageal cancer . [ 18 ] Sodium nitrate and nitrite are associated with a higher risk of colorectal cancer . [ 19 ]
Substantial evidence in recent decades, facilitated by an increased understanding of pathological processes and science, exists in support of the theory that processed meat increases the risk of colon cancer and that this is due to the nitrate content. A small amount of the nitrate added to meat as a preservative breaks down into nitrite, in addition to any nitrite that may also be added. The nitrite then reacts with protein-rich foods (such as meat) to produce carcinogenic NOCs ( nitroso compounds). NOCs can be formed either when meat is cured or in the body as meat is digested. [ 20 ]
However, several things complicate the otherwise straightforward understanding that "nitrates in food raise the risk of cancer". Processed meats have no fiber, vitamins, or phytochemical antioxidants [ citation needed ] , are high in sodium, may contain high fat, and are often fried or cooked at a temperature sufficient to degrade protein into nitrosamines. Nitrates are key intermediates and effectors in the primary vasculature signaling which is necessary for all mammals to survive. [ 21 ] | https://en.wikipedia.org/wiki/NaNO3 |
Sodium superoxide is the inorganic compound with the formula Na O 2 . [ 1 ] This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen.
NaO 2 is prepared by treating sodium peroxide with oxygen at high pressures: [ 2 ]
It can also be prepared by careful oxygenation of a solution of sodium in cryogenic liquid ammonia :
Although the existence of a sodium oxide higher than peroxide was speculated since 19th century, it was not until 1948 when American chemists were able to definitely synthesize it by the latter method. [ 3 ]
It is also produced, along with sodium peroxide , when sodium is stored under inappropriate conditions (e.g. in dirty or partially halogenated solvents) [ citation needed ] .
The product is paramagnetic , as expected for a salt of the O − 2 anion . It hydrolyses readily to give a mixture of sodium hydroxide, oxygen and hydrogen peroxide. [ 4 ] It crystallizes in the NaCl motif.
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NaO2 |
Sodium ethoxide, also referred to as sodium ethanolate , is the ionic , organic compound with the formula CH 3 CH 2 ONa , C 2 H 5 O Na , or NaOEt (Et = ethyl ). It is a white solid, although impure samples appear yellow or brown. It dissolves in polar solvents such as ethanol . It is commonly used as a strong base . [ 2 ]
Few procedures have been reported to prepare the anhydrous solid. Instead the material is typically prepared in a solution with ethanol. It is commercially available and as a solution in ethanol. It is easily prepared in the laboratory by treating sodium metal with absolute ethanol : [ 3 ]
The reaction of sodium hydroxide with anhydrous ethanol suffers from incomplete conversion to the ethoxide, but can still produce dry NaOEt by precipitation using acetone, [ 4 ] or by drying using additional NaOH. [ 5 ]
The crystal structure of sodium ethoxide has been determined by X-ray crystallography . It consists of layers of alternating Na + and O − centres with disordered ethyl groups covering the top and bottom of each layer. The ethyl layers pack back-to-back resulting in a lamellar structure . The reaction of sodium and ethanol sometimes forms other products such as the disolvate CH 3 CH 2 ONa·2 CH 3 CH 2 OH . Its crystal structure has been determined, although the structure of other phases in the CH 3 CH 2 ONa/CH 3 CH 2 OH system remain unknown. [ 6 ]
Sodium ethoxide is commonly used as a base in the Claisen condensation [ 7 ] and malonic ester synthesis . [ 8 ] Sodium ethoxide may either deprotonate the α-position of an ester molecule, forming an enolate , or the ester molecule may undergo a nucleophilic substitution called transesterification . If the starting material is an ethyl ester, trans-esterification is irrelevant since the product is identical to the starting material. In practice, the alcohol/alkoxide solvating mixture must match the alkoxy components of the reacting esters to minimize the number of different products.
Many alkoxides are prepared by salt metathesis from sodium ethoxide.
Sodium ethoxide is prone to reaction with both water and carbon dioxide in the air . [ 9 ] This leads to degradation of stored samples over time, even in solid form. The physical appearance of degraded samples may not be obvious, but samples of sodium ethoxide gradually turn dark on storage. It has been reported that even newly-obtained commercial batches of sodium ethoxide show variable levels of degradation, and responsible as a major source of irreproducibility when used in Suzuki reactions . [ 9 ]
In moist air, CH 3 CH 2 ONa hydrolyses rapidly to sodium hydroxide (NaOH). The conversion is not obvious and typical samples of CH 3 CH 2 ONa are contaminated with NaOH.
In moisture -free air, solid sodium ethoxide can form sodium ethyl carbonate from fixation of carbon dioxide from the air. Further reactions lead to degradation into a variety of other sodium salts and diethyl ether . [ 9 ]
This instability can be prevented by storing sodium ethoxide under an inert atmosphere (e.g., N 2 ).
Sodium ethoxide is a strong base , and is therefore corrosive. | https://en.wikipedia.org/wiki/NaOCH2CH3 |
Sodium hydroxide , also known as lye and caustic soda , [ 1 ] [ 2 ] is an inorganic compound with the formula NaOH . It is a white solid ionic compound consisting of sodium cations Na + and hydroxide anions OH − .
Sodium hydroxide is a highly corrosive base and alkali that decomposes lipids and proteins at ambient temperatures and may cause severe chemical burns . It is highly soluble in water , and readily absorbs moisture and carbon dioxide from the air . It forms a series of hydrates NaOH· n H 2 O . [ 13 ] The monohydrate NaOH·H 2 O crystallizes from water solutions between 12.3 and 61.8 °C. The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the anhydrous compound.
As one of the simplest hydroxides, sodium hydroxide is frequently used alongside neutral water and acidic hydrochloric acid to demonstrate the pH scale to chemistry students. [ 14 ]
Sodium hydroxide is used in many industries: in the making of wood pulp and paper , textiles , drinking water , soaps and detergents , and as a drain cleaner . Worldwide production in 2022 was approximately 83 million tons. [ 15 ]
Pure sodium hydroxide is a colorless crystalline solid that melts at 318 °C (604 °F) without decomposition and boils at 1,388 °C (2,530 °F). It is highly soluble in water, with a lower solubility in polar solvents such as ethanol and methanol . [ 16 ] Sodium hydroxide is insoluble in ether and other non-polar solvents.
Similar to the hydration of sulfuric acid, dissolution of solid sodium hydroxide in water is a highly exothermic reaction [ 17 ] where a large amount of heat is liberated, posing a threat to safety through the possibility of splashing. The resulting solution is usually colorless and odorless. As with other alkaline solutions, it feels slippery with skin contact due to the process of saponification that occurs between NaOH and natural skin oils.
Concentrated (50%) aqueous solutions of sodium hydroxide have a characteristic viscosity , 78 m Pa ·s, that is much greater than that of water (1.0 mPa·s) and near that of olive oil (85 mPa·s) at room temperature. The viscosity of aqueous NaOH , as with any liquid chemical, is inversely related to its temperature, i.e., its viscosity decreases as temperature increases, and vice versa. The viscosity of sodium hydroxide solutions plays a direct role in its application as well as its storage. [ 16 ]
Sodium hydroxide can form several hydrates NaOH· n H 2 O , which result in a complex solubility diagram that was described in detail by Spencer Umfreville Pickering in 1893. [ 18 ] The known hydrates and the approximate ranges of temperature and concentration (mass percent of NaOH) of their saturated water solutions are: [ 13 ]
Early reports refer to hydrates with n = 0.5 or n = 2/3, but later careful investigations failed to confirm their existence. [ 20 ]
The only hydrates with stable melting points are NaOH·H 2 O (65.10 °C) and NaOH·3.5H 2 O (15.38 °C). The other hydrates, except the metastable ones NaOH·3H 2 O and NaOH·4H 2 O (β) can be crystallized from solutions of the proper composition, as listed above. However, solutions of NaOH can be easily supercooled by many degrees, which allows the formation of hydrates (including the metastable ones) from solutions with different concentrations. [ 13 ] [ 20 ]
For example, when a solution of NaOH and water with 1:2 mole ratio (52.6% NaOH by mass) is cooled, the monohydrate normally starts to crystallize (at about 22 °C) before the dihydrate. However, the solution can easily be supercooled down to −15 °C, at which point it may quickly crystallize as the dihydrate. When heated, the solid dihydrate might melt directly into a solution at 13.35 °C; however, once the temperature exceeds 12.58 °C it often decomposes into solid monohydrate and a liquid solution. Even the n = 3.5 hydrate is difficult to crystallize, because the solution supercools so much that other hydrates become more stable. [ 13 ]
A hot water solution containing 73.1% (mass) of NaOH is a eutectic that solidifies at about 62.63 °C as an intimate mix of anhydrous and monohydrate crystals. [ 21 ] [ 20 ]
A second stable eutectic composition is 45.4% (mass) of NaOH, that solidifies at about 4.9 °C into a mixture of crystals of the dihydrate and of the 3.5-hydrate. [ 13 ]
The third stable eutectic has 18.4% (mass) of NaOH. It solidifies at about −28.7 °C as a mixture of water ice and the heptahydrate NaOH·7H 2 O . [ 18 ] [ 22 ]
When solutions with less than 18.4% NaOH are cooled, water ice crystallizes first, leaving the NaOH in solution. [ 18 ]
The α form of the tetrahydrate has density 1.33 g/cm 3 . It melts congruously at 7.55 °C into a liquid with 35.7% NaOH and density 1.392 g/cm 3 , and therefore floats on it like ice on water. However, at about 4.9 °C it may instead melt incongruously into a mixture of solid NaOH·3.5H 2 O and a liquid solution. [ 19 ]
The β form of the tetrahydrate is metastable, and often transforms spontaneously to the α form when cooled below −20 °C. [ 19 ] Once initiated, the exothermic transformation is complete in a few minutes, with a 6.5% increase in volume of the solid. The β form can be crystallized from supercooled solutions at −26 °C, and melts partially at −1.83 °C. [ 19 ]
The "sodium hydroxide" of commerce is often the monohydrate (density 1.829 g/cm 3 ). Physical data in technical literature may refer to this form, rather than the anhydrous compound.
NaOH and its monohydrate form orthorhombic crystals with the space groups Cmcm ( oS8 ) and Pbca (oP24), respectively. The monohydrate cell dimensions are a = 1.1825, b = 0.6213, c = 0.6069 nm . The atoms are arranged in a hydrargillite -like layer structure, with each sodium atom surrounded by six oxygen atoms, three each from hydroxide ions and three from water molecules. The hydrogen atoms of the hydroxyls form strong bonds with oxygen atoms within each O layer. Adjacent O layers are held together by hydrogen bonds between water molecules. [ 23 ]
Sodium hydroxide reacts with protic acids to produce water and the corresponding salts. For example, when sodium hydroxide reacts with hydrochloric acid , sodium chloride is formed:
In general, such neutralization reactions are represented by one simple net ionic equation:
This type of reaction with a strong acid releases heat, and hence is exothermic . Such acid–base reactions can also be used for titrations . However, sodium hydroxide is not used as a primary standard because it is hygroscopic and absorbs carbon dioxide from air.
Sodium hydroxide also reacts with acidic oxides , such as sulfur dioxide . Such reactions are often used to " scrub " harmful acidic gases (like SO 2 and H 2 S ) produced in the burning of coal and thus prevent their release into the atmosphere. For example,
Glass reacts slowly with aqueous sodium hydroxide solutions at ambient temperatures to form soluble silicates . Because of this, glass joints and stopcocks exposed to sodium hydroxide have a tendency to "freeze". Flasks and glass-lined chemical reactors are damaged by long exposure to hot sodium hydroxide, which also frosts the glass. Sodium hydroxide does not attack iron at room temperature, since iron does not have amphoteric properties (i.e., it only dissolves in acid, not base).
Nevertheless, at high temperatures (e.g. above 500 °C), iron can react endothermically with sodium hydroxide to form iron(III) oxide , sodium metal, and hydrogen gas. [ 24 ] This is due to the lower enthalpy of formation of iron(III) oxide (−824.2 kJ/mol) compared to sodium hydroxide (−500 kJ/mol) and positive entropy change of the reaction, which implies spontaneity at high temperatures ( ΔST > ΔH , ΔG < 0 ) and non-spontaneity at low temperatures ( ΔST < ΔH , ΔG > 0 ). Consider the following reaction between molten sodium hydroxide and finely divided iron filings:
A few transition metals , however, may react quite vigorously with sodium hydroxide under milder conditions.
In 1986, an aluminium road tanker in the UK was mistakenly used to transport 25% sodium hydroxide solution, [ 25 ] causing pressurization of the contents and damage to tankers. The pressurization is due to the hydrogen gas which is produced in the reaction between sodium hydroxide and aluminium:
Unlike sodium hydroxide, which is soluble, the hydroxides of most transition metals are insoluble, and therefore sodium hydroxide can be used to precipitate transition metal hydroxides. The following colours are observed:
Zinc and lead salts dissolve in excess sodium hydroxide to give a clear solution of Na 2 ZnO 2 or Na 2 PbO 2 .
Aluminium hydroxide is used as a gelatinous flocculant to filter out particulate matter in water treatment . Aluminium hydroxide is prepared at the treatment plant from aluminium sulfate by reacting it with sodium hydroxide or bicarbonate.
Sodium hydroxide can be used for the base-driven hydrolysis of esters (also called saponification ), amides and alkyl halides . [ 16 ] However, the limited solubility of sodium hydroxide in organic solvents means that the more soluble potassium hydroxide (KOH) is often preferred. Touching a sodium hydroxide solution with bare hands, while not recommended, produces a slippery feeling. This happens because oils on the skin such as sebum are converted to soap.
Despite solubility in propylene glycol it is unlikely to replace water in saponification due to propylene glycol's primary reaction with fat before reaction between sodium hydroxide and fat.
Sodium hydroxide is industrially produced, first as a 32% solution, and then evaporated to a 50% solution by variations of the electrolytic chloralkali process . [ 26 ] Chlorine gas is the main product from this process. [ 27 ] [ 26 ] Solid sodium hydroxide is obtained from this solution by the evaporation of water. Solid sodium hydroxide is most commonly sold as flakes, prills , and cast blocks. [ 28 ]
In 2022, world production was estimated at 83 million dry tonnes of sodium hydroxide, and demand was estimated at 51 million tonnes. [ 28 ] In 1998, total world production was around 45 million tonnes . North America and Asia each contributed around 14 million tonnes, while Europe produced around 10 million tonnes. In the United States, the major producer of sodium hydroxide is Olin , which has annual production around 5.7 million tonnes from sites at Freeport, Texas ; Plaquemine, Louisiana ; St. Gabriel, Louisiana ; McIntosh, Alabama ; Charleston, Tennessee ; Niagara Falls, New York ; and Bécancour, Canada . Other major US producers include Oxychem , Westlake , Shintek, and Formosa . All of these companies use the chloralkali process . [ 29 ]
Historically, sodium hydroxide was produced by treating sodium carbonate with calcium hydroxide (slaked lime) in a metathesis reaction which takes advantage of the fact that sodium hydroxide is soluble, while calcium carbonate is not. This process was called causticizing. [ 30 ]
The sodium carbonate for this reaction was produced by the Leblanc process in the early 19th century, or the Solvay process in the late 19th century. The conversion of sodium carbonate to sodium hydroxide was superseded entirely by the chloralkali process , which produces sodium hydroxide in a single process.
Sodium hydroxide is also produced by combining pure sodium metal with water. The byproducts are hydrogen gas and heat, often resulting in a flame.
This reaction is commonly used for demonstrating the reactivity of alkali metals in academic environments; however, it is not used commercially aside from a reaction within the mercury cell chloralkali process where sodium amalgam is reacted with water.
Sodium hydroxide is a popular strong base used in industry. Sodium hydroxide is used in the manufacture of sodium salts and detergents, pH regulation, and organic synthesis. In bulk, it is most often handled as an aqueous solution , [ 31 ] since solutions are cheaper and easier to handle.
Sodium hydroxide is used in many scenarios where it is desirable to increase the alkalinity of a mixture, or to neutralize acids. For example, in the petroleum industry, sodium hydroxide is used as an additive in drilling mud to increase alkalinity in bentonite mud systems, to increase the mud viscosity , and to neutralize any acid gas (such as hydrogen sulfide and carbon dioxide ) which may be encountered in the geological formation as drilling progresses. Another use is in salt spray testing where pH needs to be regulated. Sodium hydroxide is used with hydrochloric acid to balance pH. The resultant salt, NaCl, is the corrosive agent used in the standard neutral pH salt spray test.
Poor quality crude oil can be treated with sodium hydroxide to remove sulfurous impurities in a process known as caustic washing . Sodium hydroxide reacts with weak acids such as hydrogen sulfide and mercaptans to yield non-volatile sodium salts, which can be removed. The waste which is formed is toxic and difficult to deal with, and the process is banned in many countries because of this. In 2006, Trafigura used the process and then dumped the waste in Ivory Coast . [ 32 ] [ 33 ]
Other common uses of sodium hydroxide include:
Sodium hydroxide is also widely used in pulping of wood for making paper or regenerated fibers. Along with sodium sulfide , sodium hydroxide is a key component of the white liquor solution used to separate lignin from cellulose fibers in the kraft process . It also plays a key role in several later stages of the process of bleaching the brown pulp resulting from the pulping process. These stages include oxygen delignification, oxidative extraction, and simple extraction, all of which require a strong alkaline environment with a pH > 10.5 at the end of the stages.
In a similar fashion, sodium hydroxide is used to digest tissues, as in a process that was used with farm animals at one time. This process involved placing a carcass into a sealed chamber, then adding a mixture of sodium hydroxide and water (which breaks the chemical bonds that keep the flesh intact). This eventually turns the body into a liquid with a dark brown color, [ 36 ] [ 37 ] and the only solids that remain are bone hulls, which can be crushed between one's fingertips. [ 38 ]
Sodium hydroxide is frequently used in the process of decomposing roadkill dumped in landfills by animal disposal contractors. [ 37 ] Due to its availability and low cost, it has been used by criminals to dispose of corpses. Italian serial killer Leonarda Cianciulli used this chemical to turn dead bodies into soap. [ 39 ] In Mexico, a man who worked for drug cartels admitted disposing of over 300 bodies with it. [ 40 ]
Sodium hydroxide is a dangerous chemical due to its ability to hydrolyze protein. If a dilute solution is spilled on the skin, burns may result if the area is not washed thoroughly and for several minutes with running water. Splashes in the eye can be more serious and can lead to blindness. [ 41 ]
Strong bases attack aluminium . Sodium hydroxide reacts with aluminium and water to release hydrogen gas. The aluminium takes an oxygen atom from sodium hydroxide, which in turn takes an oxygen atom from water, and releases two hydrogen atoms. The reaction thus produces hydrogen gas and sodium aluminate . In this reaction, sodium hydroxide acts as an agent to make the solution alkaline, which aluminium can dissolve in.
Sodium aluminate is an inorganic chemical that is used as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as NaAlO 2 , Na 3 AlO 3 , Na[Al(OH) 4 ] , Na 2 O·Al 2 O 3 or Na 2 Al 2 O 4 . Formation of sodium tetrahydroxoaluminate(III) or hydrated sodium aluminate is given by: [ 42 ]
This reaction can be useful in etching , removing anodizing, or converting a polished surface to a satin-like finish, but without further passivation such as anodizing or alodining the surface may become degraded, either under normal use or in severe atmospheric conditions.
In the Bayer process , sodium hydroxide is used in the refining of alumina containing ores ( bauxite ) to produce alumina ( aluminium oxide ) which is the raw material used to produce aluminium via the electrolytic Hall-Héroult process . Since the alumina is amphoteric , it dissolves in the sodium hydroxide, leaving impurities less soluble at high pH such as iron oxides behind in the form of a highly alkaline red mud .
Other amphoteric metals are zinc and lead which dissolve in concentrated sodium hydroxide solutions to give sodium zincate and sodium plumbate respectively.
Sodium hydroxide is traditionally used in soap making ( cold process soap, saponification ). [ 43 ] It was made in the nineteenth century for a hard surface rather than liquid product because it was easier to store and transport.
For the manufacture of biodiesel , sodium hydroxide is used as a catalyst for the transesterification of methanol and triglycerides. This only works with anhydrous sodium hydroxide, because combined with water the fat would turn into soap , which would be tainted with methanol . NaOH is used more often than potassium hydroxide because it is cheaper and a smaller quantity is needed. Due to production costs, NaOH, which is produced using common salt is cheaper than potassium hydroxide. [ 44 ]
Sodium hydroxide is an ingredient used in some skin care and cosmetic products, such as facial cleansers, creams, lotions, and makeup. It is typically used in low concentration as a pH balancer , due its highly alkaline nature. [ 45 ]
Food uses of sodium hydroxide include washing or chemical peeling of fruits and vegetables , chocolate and cocoa processing, caramel coloring production, poultry scalding, soft drink processing, and thickening ice cream . [ 46 ] Olives are often soaked in sodium hydroxide for softening; pretzels and German lye rolls are glazed with a sodium hydroxide solution before baking to make them crisp. Owing to the difficulty in obtaining food grade sodium hydroxide in small quantities for home use, sodium carbonate is often used in place of sodium hydroxide. [ 47 ] It is known as E number E524.
Specific foods processed with sodium hydroxide include:
Sodium hydroxide is frequently used as an industrial cleaning agent where it is often called "caustic". It is added to water, heated, and then used to clean process equipment, storage tanks, etc. It can dissolve grease , oils , fats and protein -based deposits. It is also used for cleaning waste discharge pipes under sinks and drains in domestic properties. Surfactants can be added to the sodium hydroxide solution in order to stabilize dissolved substances and thus prevent redeposition. A sodium hydroxide soak solution is used as a powerful degreaser on stainless steel and glass bakeware. It is also a common ingredient in oven cleaners.
A common use of sodium hydroxide is in the production of parts washer detergents . Parts washer detergents based on sodium hydroxide are some of the most aggressive parts washer cleaning chemicals. The sodium hydroxide-based detergents include surfactants, rust inhibitors and defoamers. A parts washer heats water and the detergent in a closed cabinet and then sprays the heated sodium hydroxide and hot water at pressure against dirty parts for degreasing applications. Sodium hydroxide used in this manner replaced many solvent-based systems in the early 1990s [ citation needed ] when trichloroethane was outlawed by the Montreal Protocol . Water and sodium hydroxide detergent-based parts washers are considered to be an environmental improvement over the solvent-based cleaning methods.
Sodium hydroxide is used in the home as a type of drain openers to unblock clogged drains, usually in the form of a dry crystal or as a thick liquid gel. The alkali reacts with greases to produce water soluble soap and glycerol . It also hydrolyzes proteins , such as those found in hair , which may block waste water pipes. Dissolving sodium hydroxide in water is an exothermic reaction producing considerable quantities of heat which assists in speeding up the reactions with grease and other organic matter. Such alkaline drain cleaners and their acidic versions are highly corrosive and should be handled with great caution.
Sodium hydroxide is used in some relaxers to straighten hair . However, because of the high incidence and intensity of chemical burns, manufacturers of chemical relaxers use other alkaline chemicals in preparations available to consumers. Sodium hydroxide relaxers are still available, but they are used mostly by professionals.
A solution of sodium hydroxide in water was traditionally used as the most common paint stripper on wooden objects. Its use has become less common, because it can damage the wood surface, raising the grain and staining the colour.
Sodium hydroxide is sometimes used during water purification to raise the pH of water supplies. Increased pH makes the water less corrosive to plumbing and reduces the amount of lead, copper and other toxic metals that can dissolve into drinking water. [ 49 ] [ 50 ]
Sodium hydroxide has been used for detection of carbon monoxide poisoning , with blood samples of such patients turning to a vermilion color upon the addition of a few drops of sodium hydroxide. [ 51 ] Today, carbon monoxide poisoning can be detected by CO oximetry .
Sodium hydroxide is used in some cement mix plasticisers. This helps homogenise cement mixes, preventing segregation of sands and cement, decreases the amount of water required in a mix and increases workability of the cement product, be it mortar, render or concrete.
Like other corrosive acids and alkalis , a few drops of sodium hydroxide solutions can readily decompose proteins and lipids in living tissues via amide hydrolysis and ester hydrolysis , which consequently cause chemical burns and may induce permanent blindness upon contact with eyes. [ 1 ] [ 2 ] Solid alkali can also express its corrosive nature if there is water, such as water vapor. Thus, protective equipment , like rubber gloves , safety clothing and eye protection , should always be used when handling this chemical or its solutions. The standard first aid measures for alkali spills on the skin is, as for other corrosives, irrigation with large quantities of water. Washing is continued for at least ten to fifteen minutes.
Moreover, dissolution of sodium hydroxide is highly exothermic , and the resulting heat may cause heat burns or ignite flammables. It also produces heat when reacted with acids.
Sodium hydroxide is mildly corrosive to glass , which can cause damage to glazing or cause ground glass joints to bind. [ 52 ] Sodium hydroxide is corrosive to several metals, like aluminium which reacts with the alkali to produce flammable hydrogen gas on contact. [ 53 ]
Sodium hydroxide's toxicity level for fish etc. is around 20—200 mg/l and associated with increased pH value. However as it is quickly neutralised and does not accumulate, its effect on the environment is usually easily handled. [ 54 ]
Careful storage is needed when handling sodium hydroxide for use, especially bulk volumes. Following proper NaOH storage guidelines and maintaining worker/environment safety is always recommended given the chemical's burn hazard.
Sodium hydroxide is often stored in bottles for small-scale laboratory use, within intermediate bulk containers (medium volume containers) for cargo handling and transport, or within large stationary storage tanks with volumes up to 100,000 gallons for manufacturing or waste water plants with extensive NaOH use. Common materials that are compatible with sodium hydroxide and often utilized for NaOH storage include: polyethylene ( HDPE , usual, XLPE , less common), carbon steel , polyvinyl chloride (PVC), stainless steel , and fiberglass reinforced plastic (FRP, with a resistant liner). [ 16 ]
Sodium hydroxide must be stored in airtight containers to preserve its normality as it will absorb water and carbon dioxide from the atmosphere.
Sodium hydroxide was first prepared by soap makers. [ 55 ] : p45 A procedure for making sodium hydroxide appeared as part of a recipe for making soap in an Arab book of the late 13th century: Al-mukhtara' fi funun min al-suna' (Inventions from the Various Industrial Arts), which was compiled by al-Muzaffar Yusuf ibn 'Umar ibn 'Ali ibn Rasul (d. 1295), a king of Yemen . [ 56 ] [ 57 ]
The recipe called for passing water repeatedly through a mixture of alkali (Arabic: al-qily , where qily is ash from saltwort plants, which are rich in sodium; hence alkali was impure sodium carbonate ) [ 58 ] and quicklime ( calcium oxide , CaO), whereby a solution of sodium hydroxide was obtained. European soap makers also followed this recipe. When in 1791 the French chemist and surgeon Nicolas Leblanc (1742–1806) patented a process for mass-producing sodium carbonate , natural "soda ash" (impure sodium carbonate that was obtained from the ashes of plants that are rich in sodium) [ 55 ] : p36 was replaced by this artificial version. [ 55 ] : p46 However, by the 20th century, the electrolysis of sodium chloride had become the primary method for producing sodium hydroxide. [ 59 ] | https://en.wikipedia.org/wiki/NaOH |
Sodium hypoiodite is an inorganic chemical used as an oxidant in various organic chemical reactions. It causes iodination of nitrogen atoms, such 1 H -benzotriazole to give 1-iodo-1 H -benzotriazole and an imine to give the analogous iodoimine. [ 1 ] It oxidatively cleaves methyl ketones to give iodoform . [ 2 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NaOI |
Sodium methoxide is the simplest sodium alkoxide . With the formula CH 3 ONa , it is a white solid, which is formed by the deprotonation of methanol . It is a widely used reagent in industry and the laboratory. It is also a dangerously caustic base .
Sodium methoxide is prepared by treating methanol with sodium:
The reaction is so exothermic that ignition is possible. The resulting solution, which is colorless, is often used as a source of sodium methoxide, but the pure material can be isolated by evaporation followed by heating to remove residual methanol.
As a solid, sodium methoxide is polymeric , with sheet-like arrays of Na + centers, each bonded to four oxygen centers. [ 3 ]
The structure, and hence the basicity, of sodium methoxide in solution depends on the solvent. It is a significantly stronger base in DMSO where it is more fully ionized and free of hydrogen bonding . [ 4 ]
Sodium methoxide is a routinely used base in organic chemistry, applicable to the synthesis of numerous compounds ranging from pharmaceuticals to agrichemicals . [ 4 ] As a base, it is employed in dehydrohalogenations and various condensations . [ 5 ] It is also a nucleophile for the production of methyl ethers . [ 6 ]
Sodium methoxide is used as an initiator of anionic addition polymerization with ethylene oxide , forming a polyether with high molecular weight. [ 7 ] Biodiesel is prepared from vegetable oils and animal fats (fatty acid triglycerides) by transesterification with methanol to give fatty acid methyl esters (FAMEs). Sodium methoxide acts as a catalyst for this reaction, but will combine with any free fatty acids present in the oil/fat feedstock to form soap byproducts. [ citation needed ]
The solid hydrolyzes in water to give methanol and sodium hydroxide . Indeed, samples of sodium methoxide are often contaminated with sodium hydroxide, which is difficult to detect. The compound absorbs carbon dioxide from the air to form methanol and sodium carbonate , thus diminishing the alkalinity of the base. [ citation needed ]
Commercial batches of sodium methoxide show variable levels of degradation, and were a major source of irreproducibility when used in Suzuki reactions . [ 8 ]
Sodium methoxide is highly caustic and reacts with water to give methanol , which is toxic and volatile.
The ratings for this substance vary widely. | https://en.wikipedia.org/wiki/NaOMe |
In materials science , Nabarro–Herring creep ( NH creep ) is a mechanism of deformation of crystalline materials (and amorphous materials [ 1 ] ) that occurs at low stresses and held at elevated temperatures in fine-grained materials. In Nabarro–Herring creep, atoms diffuse through the crystals, and the rate of creep varies inversely with the square of the grain size so fine-grained materials creep faster than coarser-grained ones. [ 2 ] [ 3 ] NH creep is solely controlled by diffusional mass transport . [ 1 ]
This type of creep results from the diffusion of vacancies from regions of high chemical potential at grain boundaries subjected to normal tensile stresses to regions of lower chemical potential where the average tensile stresses across the grain boundaries are zero. Self-diffusion within the grains of a polycrystalline solid can cause the solid to yield to an applied shear stress , the yielding being caused by a diffusional flow of matter within each crystal grain away from boundaries where there is a normal pressure and toward those where there is a normal tension. [ 4 ] Atoms migrating in the opposite direction account for the creep strain ( ε NH ). The creep strain rate is derived in the next section. NH creep is more important in ceramics than metals as dislocation motion is more difficult to effect in ceramics. [ 1 ]
Source: [ 1 ]
The Nabarro–Herring creep rate, ε ˙ N H {\displaystyle {\dot {\varepsilon }}_{\rm {NH}}} , can be derived by considering an individual rectangular grain (in a single or polycrystal). [ 1 ] Two opposing sides have a compressive stress applied and the other two have a tensile stress applied. The atomic volume is decreased by compression and increased by tension. Under this change, the activation energy to form a vacancy is altered by ± σ Ω {\displaystyle \pm \sigma \Omega } . The atomic volume is Ω {\displaystyle \Omega } and the stress is σ {\displaystyle \sigma } . The plus and minus indication is an increase or decrease in the activation energy due to the tensile and compressive stresses, respectively. The fraction of vacancy concentrations in the compressive ( N ν C {\displaystyle N_{\nu }^{C}} ) and tensile ( N ν T {\displaystyle N_{\nu }^{T}} ) regions are given as:
In these equations Q f {\displaystyle Q_{f}} is the vacancy formation energy, k {\displaystyle k} is the Boltzmann constant , and T {\displaystyle T} is the absolute temperature . These vacancy concentrations are maintained at the lateral and horizontal surfaces in the grain. These net concentrations drive vacancies to the compressive regions from the tensile ones which causes grain elongation in one dimension and grain compression in the other. This is creep deformation caused by a flux of vacancy motion.
The vacancy flux , J ν {\displaystyle J_{\nu }} , associated with this motion is given by:
where D ν {\displaystyle D_{\nu }} is the vacancy diffusivity. This is given as:
where D 0 ν {\displaystyle D_{0\nu }} is the diffusivity when 0 vacancies are present and Q m {\displaystyle Q_{m}} is the vacancy motion energy. The term δ N ν δ x {\displaystyle {\tfrac {\delta N_{\nu }}{\delta x}}} is the vacancy concentration gradient. The term δ x {\displaystyle \delta x} is proportional to the grain size d {\displaystyle d} and δ N ν = N ν T − N ν C {\displaystyle \delta N_{\nu }=N_{\nu }^{T}-N_{\nu }^{C}} . If we multiply J ν {\displaystyle J_{\nu }} by d 2 {\displaystyle d^{2}} we obtain:
where δ V δ t {\displaystyle {\tfrac {\delta V}{\delta t}}} is the volume changed per unit time during creep deformation. The change in volume can be related to the change in length along the tensile axis as δ V ≈ d 2 δ d {\displaystyle \delta V\approx d^{2}\delta d} . Using the relationship between δ V {\displaystyle \delta V} and δ d {\displaystyle \delta d} the NH creep rate is given by:
This equation can be greatly simplified. The lattice self-diffusion coefficient is given by:
As previously stated, NH creep occurs at low stresses and high temperatures. In this range σ Ω << k T {\displaystyle \sigma \Omega <<kT} . For small x {\displaystyle x} , exp ( ± x ) ≈ 1 ± x {\displaystyle \exp(\pm x)\approx 1\pm x} . Thus we can re-write ε ˙ N H {\displaystyle {\dot {\varepsilon }}_{\rm {NH}}} as:
where A N H {\displaystyle A_{\rm {NH}}} is a constant that absorbs the approximations in the derivation.
Alternatively, this can be derived in a different method where the constant A n {\displaystyle A_{n}} has different dimensions. In this case, the NH creep rate ε ˙ {\displaystyle {\dot {\varepsilon }}} is given by: [ 5 ]
Coble creep is closely related to Nabarro–Herring creep and is controlled by diffusion as well. Unlike Nabarro–Herring creep, mass transport occurs by diffusion along the surface of single crystals or the grain boundaries in a polycrystal. [ 1 ] For a general expression of creep rate, the comparison between Nabarro–Herring and Coble creep can be presented as follows: [ 6 ]
G is the shear modulus . The diffusivity is obtained form the tracer diffusivity, D ∗ {\displaystyle D^{*}} . The dimensionless constant A n {\displaystyle A_{n}} depends intensively on the geometry of grains. The parameters A {\displaystyle A} , n {\displaystyle n} and p {\displaystyle p} are dependent on creep mechanisms. Nabbaro–Herring creep does not involve the motion of dislocations. It predominates over high-temperature dislocation-dependent mechanisms only at low stresses, and then only for fine-grained materials. Nabarro–Herring creep is characterized by creep rates that increase linearly with the stress and inversely with the square of grain diameter.
In contrast, in Coble creep atoms diffuse along grain boundaries and the creep rate varies inversely with the cube of the grain size. [ 2 ] Lower temperatures favor Coble creep and higher temperatures favor Nabbaro–Herring creep because the activation energy for vacancy diffusion within the lattice is typically larger than that along the grain boundaries, thus lattice diffusion slows down relative to grain boundary diffusion with decreasing temperature. [ 2 ] | https://en.wikipedia.org/wiki/Nabarro–Herring_creep |
The nabla is a triangular symbol resembling an inverted Greek delta : [ 1 ] ∇ {\displaystyle \nabla } or ∇. The name comes, by reason of the symbol's shape, from the Hellenistic Greek word νάβλα for a Phoenician harp , [ 2 ] [ 3 ] and was suggested by the encyclopedist William Robertson Smith in an 1870 letter to Peter Guthrie Tait . [ 2 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The nabla symbol is available in standard HTML as ∇ and in LaTeX as \nabla . In Unicode , it is the character at code point U+2207, or 8711 in decimal notation, in the Mathematical Operators block.
As an operator, it is often called del .
The differential operator given in Cartesian coordinates { x , y , z } {\displaystyle \{x,y,z\}} on three-dimensional Euclidean space by
was introduced in 1831 by the Irish mathematician and physicist William Rowan Hamilton , who called it ◁. [ 8 ] (The unit vectors { i , j , k } {\displaystyle \{\mathbf {i} ,\mathbf {j} ,\mathbf {k} \}} were originally right versors in Hamilton's quaternions .) The mathematics of ∇ received its full exposition at the hands of P. G. Tait . [ 9 ] [ 10 ]
After receiving Smith's suggestion, Tait and James Clerk Maxwell referred to the operator as nabla in their extensive private correspondence; most of these references are of a humorous character. C. G. Knott's Life and Scientific Work of Peter Guthrie Tait (p. 145): [ 5 ]
It was probably this reluctance on the part of Maxwell to use the term Nabla in serious writings which prevented Tait from introducing the word earlier than he did. The one published use of the word by Maxwell is in the title to his humorous Tyndallic Ode, which is dedicated to the "Chief Musician upon Nabla", that is, Tait.
William Thomson (Lord Kelvin) introduced the term to an American audience in an 1884 lecture; [ 2 ] the notes were published in Britain and the U.S. in 1904. [ 11 ]
The name is acknowledged, and criticized, by Oliver Heaviside in 1891: [ 12 ]
The fictitious vector ∇ given by
is very important. Physical mathematics is very largely the mathematics of ∇. The name Nabla seems, therefore, ludicrously inefficient.
Heaviside and Josiah Willard Gibbs (independently) are credited with the development of the version of vector calculus most popular today. [ 13 ]
The influential 1901 text Vector Analysis , written by Edwin Bidwell Wilson and based on the lectures of Gibbs, advocates the name "del": [ 14 ]
This symbolic operator ∇ was introduced by Sir W. R. Hamilton and is now in universal employment. There seems, however, to be no universally recognized name for it, although owing to the frequent occurrence of the symbol some name is a practical necessity. It has been found by experience that the monosyllable del is so short and easy to pronounce that even in complicated formulae in which ∇ occurs a number of times, no inconvenience to the speaker or listener arises from the repetition. ∇ V is read simply as "del V ".
This book is responsible for the form in which the mathematics of the operator in question is now usually expressed—most notably in undergraduate physics, and especially electrodynamics, textbooks.
The nabla is used in vector calculus as part of three distinct differential operators: the gradient (∇), the divergence (∇⋅), and the curl (∇×). The last of these uses the cross product and thus makes sense only in three dimensions; the first two are fully general. They were all originally studied in the context of the classical theory of electromagnetism, and contemporary university physics curricula typically treat the material using approximately the concepts and notation found in Gibbs and Wilson's Vector Analysis .
The symbol is also used in differential geometry to denote a connection .
A symbol of the same form, though presumably not genealogically related, appears in other areas, e.g.:
My dear Sir, The name I propose for ∇ is, as you will remember, Nabla... In Greek the leading form is ναβλᾰ... As to the thing it is a sort of harp and is said by Hieronymus and other authorities to have had the figure of ∇ (an inverted Δ).
We can represent cases of this form, cases where it is indeterminate whether in fiction f : a = b , as follows:
(A) ∇[ f a = b ] f . | https://en.wikipedia.org/wiki/Nabla_symbol |
NacNac is a class of anionic bidentate ligands . 1,3-Di ketimines are often referred to as "HNacNac", a modification of the abbreviation H acac used for 1,3- diketones . These species can exist as a mixture of tautomers . [ 1 ]
Acetylacetone and related 1,3-diketones condense with primary alkyl- or aryl amines resulting in replacement of the carbonyl oxygen atoms with NR groups, where R = aryl , alkyl . To prepare 1,3-diketimines from bulky amines, e.g. 2,4,6-trimethylanilines , prolonged reaction times are required. 2,6-Diisopropylaniline is a common bulky building block.
Deprotonation of HNacNac compounds affords anionic bidentate ligands that form a variety of coordination complexes . [ 2 ] Some derivatives with large R groups can be used to stabilize low valent main group and transition metal complexes. [ 3 ] Unlike the situation for the acetylacetonates , the steric properties of the coordinating atoms in NacNac − ligands is adjustable by changes in the R substituent. Attachment to a metal center is usually carried out by initial deprotonation of HNacNac with n -butyllithium ; the lithium derivative is then treated with a metal chloride to eliminate lithium chloride . In some cases, HNacNacs also serve as charge-neutral 1,3-diimine ligands.
NacNac ligands are diimine analogues of acetylacetonate ligands . An intermediate class of ligands are derived from monoimino-ketones. [ 5 ] [ 6 ] The first Dipp-NacNac ligand was synthesized by Dr. Francis S. Mair in 1998. [ 7 ] | https://en.wikipedia.org/wiki/NacNac |
Sodium chloride / ˌ s oʊ d i ə m ˈ k l ɔːr aɪ d / , [ 8 ] commonly known as edible salt , is an ionic compound with the chemical formula NaCl , representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic , and occurs as the mineral halite . In its edible form, it is commonly used as a condiment and food preservative . Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses . Another major application of sodium chloride is deicing of roadways in sub-freezing weather.
In addition to the many familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing. [ 9 ]
Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production. [ 10 ]
It is the starting point for the chloralkali process , the industrial process to produce chlorine and sodium hydroxide , according to the chemical equation
This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from the sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include PVC thermoplastics production, disinfectants, and solvents.
Sodium hydroxide is extensively used in many different industries enabling production of paper, soap, aluminum, and more.
Sodium chloride is used in the Solvay process to produce sodium carbonate and calcium chloride . Sodium carbonate, in turn, is used to produce glass , sodium bicarbonate , and dyes , as well as a myriad of other chemicals. In the Mannheim process , sodium chloride is used for the production of sodium sulfate and hydrochloric acid .
Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt is an important component of drilling fluids in well drilling. [ 11 ] It is used to flocculate and increase the density of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum. [ 9 ] Salt is also used to increase the curing of concrete in cemented casings. [ 10 ]
In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, [ 12 ] to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to increase yield in dyebaths and make the colors look sharper. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes. [ 10 ]
For use in the pulp and paper industry , it is used to manufacture sodium chlorate , which is then reacted with sulfuric acid and a reducing agent such as methanol to manufacture chlorine dioxide , a bleaching chemical that is widely used to bleach wood pulp .
In tanning and leather treatment, salt is added to animal hides to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides. [ 10 ]
In rubber manufacture, salt is used to make buna , neoprene , and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified latex made from chlorinated butadiene . [ 10 ] [ 9 ]
Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load. [ 10 ]
Hard water contains calcium and magnesium ions that interfere with action of soap and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use ion-exchange resins to remove ions that cause the hardness. These resins are generated and regenerated using sodium chloride. [ 10 ] [ 9 ]
The second major application of salt is for deicing and anti-icing of roads, both in grit bins and spread by winter service vehicles . In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated solution of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For deicing, mixtures of brine and salt are used, sometimes with additional agents such as calcium chloride and/or magnesium chloride . The use of salt or brine becomes ineffective below −10 °C (14 °F).
Salt for deicing in the United Kingdom predominantly comes from a single mine in Winsford in Cheshire . Prior to distribution it is mixed with <100 ppm of sodium ferrocyanide as an anticaking agent , which enables rock salt to flow freely out of the gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on the road longer, the treatment did not have to be repeated several times, saving time and money. [ 10 ]
In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is −21.12 °C (−6.02 °F) for 23.31 wt% of salt. Freezing near this concentration is however so slow that the eutectic point of −22.4 °C (−8.3 °F) can be reached with about 25 wt% of salt. [ 13 ]
Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their osmoregulation ability. [ 14 ] The omnipresence of salt in coastal areas poses a problem in any coating application, because trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal salt concentrations on surfaces are dependent on the authority and application. The IMO regulation is mostly used and sets salt levels to a maximum of 50 mg/m 2 soluble salts measured as sodium chloride. These measurements are done by means of a Bresle test . Salinization (increasing salinity, aka freshwater salinization syndrome ) and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways. [ 15 ]
In highway de-icing, salt has been associated with corrosion of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. Surface runoff , vehicle spraying, and windblown salt also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage, the spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied. [ 10 ] A 2009 study found that approximately 70% of the road salt being applied in the Minneapolis-St Paul metro area is retained in the local watershed. [ 16 ]
Some agencies are substituting beer , molasses , and beet juice instead of road salt. [ 17 ] Airlines utilize more glycol and sugar rather than salt-based solutions for deicing. [ 18 ]
Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder, fermentation -control additive, texture-control agent, and color developer. The salt consumption in the food industry is subdivided, in descending order of consumption, into other food processing, meat packers, canning , baking, dairy, and grain mill products. Salt is added to promote color development in bacon, ham and other processed meat products. As a preservative, salt inhibits the growth of bacteria. Salt acts as a binder in sausages to form a binding gel made up of meat, fat, and moisture. Salt also acts as a flavor enhancer and as a tenderizer . [ 10 ]
It is used as a cheap and safe desiccant because of its hygroscopic properties, making salting an effective method of food preservation historically; the salt draws water out of bacteria through osmotic pressure , keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest. Many microorganisms cannot live in a salty environment: water is drawn out of their cells by osmosis . For this reason salt is used to preserve some foods, such as bacon, fish, or cabbage.
In many dairy industries, salt is added to cheese as a color-, fermentation-, and texture-control agent. The dairy subsector includes companies that manufacture creamery butter, condensed and evaporated milk, frozen desserts, ice cream, natural and processed cheese, and specialty dairy products. In canning, salt is primarily added as a flavor enhancer and preservative . It also is used as a carrier for other ingredients, dehydrating agent, enzyme inhibitor and tenderizer. In baking, salt is added to control the rate of fermentation in bread dough. It also is used to strengthen the gluten (the elastic protein-water complex in certain doughs) and as a flavor enhancer, such as a topping on baked goods. The food-processing category also contains grain mill products. These products consist of milling flour and rice and manufacturing cereal breakfast food and blended or prepared flour. Salt is also used a seasoning agent in products such as potato chips, pretzels , and cat and dog food. [ 10 ]
Sodium chloride is used in veterinary medicine as emesis -causing agent. It is given as warm saturated solution. Emesis can also be caused by pharyngeal placement of small amount of plain salt or salt crystals.
For watering plants to use sodium chloride ( NaCl ) as a fertilizer, moderate concentration is used to avoid potential toxicity: 1–3 grams (0.035–0.106 oz) per liter is generally safe and effective for most plants. [ 19 ] [ 20 ] [ 21 ]
Sodium chloride is used together with water as one of the primary solutions for intravenous therapy . Nasal spray often contains a saline solution.
Sodium chloride is also available as an oral tablet and is taken to treat low sodium levels. [ 22 ]
Sodium chloride is the principal extinguishing agent in dry-powder fire extinguishers that are used on combustible metal fires, for metals such as magnesium, zirconium, titanium, and lithium (Class D extinguishers). The salt forms an oxygen-excluding crust that smothers the fire. [ 23 ]
Since at least medieval times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of shampoo and toothpaste and is commonly used to deice driveways, parking lots, and walkways.
Sodium chloride crystals have a transmittance of at least 90% (through 1 mm) for infrared light having wavelengths in the range 0.2– 18 μm . [ 24 ] They were used in optical components such as windows and lenses, where few non-absorbing alternatives existed in that spectral range. While inexpensive, NaCl crystals are soft and hygroscopic – when exposed to the water in ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum-sealed areas, or short-term uses such as prototyping. Materials that are mechanically stronger and less sensitive to moisture, such as zinc selenide and chalcogenide glasses , more widely used than NaCl.
In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular octahedron . In the language of close-packing , the larger chloride ions (167 pm in size [ 25 ] ) are arranged in a cubic array whereas the smaller sodium ions (116 pm [ 25 ] ) fill all the cubic gaps (octahedral voids) between them. This same basic structure is found in many other compounds and is commonly known as the NaCl structure or rock salt crystal structure. It can be represented as a face-centered cubic (fcc) lattice with a two-atom basis or as two interpenetrating face centered cubic lattices. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the fcc unit cell edge.
Solid sodium chloride has a melting point of 801 °C and liquid sodium chloride boils at 1465 °C. Atomic-resolution real-time video imaging allows visualization of the initial stage of crystal nucleation of sodium chloride. [ 26 ]
The Thermal conductivity of sodium chloride as a function of temperature has a maximum of 2.03 W/(cm K) at 8 K (−265.15 °C; −445.27 °F) and decreases to 0.069 at 314 K (41 °C; 106 °F). It also decreases with doping . [ 27 ]
From cold (sub-freezing) solutions, salt crystallises with water of hydration as hydrohalite (the dihydrate NaCl·2 H 2 O ). [ 29 ]
In 2023, it was discovered that under pressure, sodium chloride can form the hydrates NaCl·8.5H 2 O and NaCl·13H 2 O. [ 30 ]
The attraction between the Na + and Cl − ions in the solid is so strong that only highly polar solvents like water dissolve NaCl well.
When dissolved in water, the sodium chloride framework disintegrates as the Na + and Cl − ions become surrounded by polar water molecules. These solutions consist of metal aquo complex with the formula [Na(H 2 O) 8 ] + , with the Na–O distance of 250 pm . The chloride ions are also strongly solvated, each being surrounded by an average of six molecules of water. [ 31 ] Solutions of sodium chloride have very different properties from pure water. The eutectic point is −21.12 °C (−6.02 °F) for 23.31% mass fraction of salt, and the boiling point of saturated salt solution is near 108.7 °C (227.7 °F). [ 13 ]
The pH of a sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl − ion, which is the conjugate base of the strong acid HCl . In other words, NaCl has no effect on system pH [ 32 ] in diluted solutions where the effects of ionic strength and activity coefficients are negligible.
Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different stoichiometries have been discovered; five new compounds were predicted (e.g., Na 3 Cl , Na 2 Cl , Na 3 Cl 2 , NaCl 3 , and NaCl 7 ). The existence of some of them has been experimentally confirmed at high pressures and other conditions: cubic and orthorhombic NaCl 3 , two-dimensional metallic tetragonal Na 3 Cl and exotic hexagonal NaCl. [ 34 ] This indicates that compounds violating chemical intuition are possible, in simple systems under non-ambient conditions. [ 35 ]
Salt is found in the Earth's crust as the mineral halite (rock salt), and a tiny amount exists as suspended sea salt particles in the atmosphere. [ 36 ] These particles are the dominant cloud condensation nuclei far out at sea, which allow the formation of clouds in otherwise non-polluted air . [ 37 ]
Salt is currently mass-produced by evaporation of seawater or brine from brine wells and salt lakes . Mining of rock salt is also a major source. China is the world's main supplier of salt. [ 10 ] In 2017, world production was estimated at 280 million tonnes , the top five producers (in million tonnes) being China (68.0), United States (43.0), India (26.0), Germany (13.0), and Canada (13.0). [ 38 ] Salt is also a byproduct of potassium mining. | https://en.wikipedia.org/wiki/Nacl |
C H 1 , C L : constant domains of antibody fragment
Nacolomab tafenatox is a mouse monoclonal antibody . [ 1 ] [ 2 ] The antibody itself, nacolomab, is fused with enterotoxin A from Staphylococcus aureus (which is reflected by 'tafenatox' in the drug's name). [ 1 ]
This monoclonal antibody –related article is a stub . You can help Wikipedia by expanding it .
This antineoplastic or immunomodulatory drug article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nacolomab_tafenatox |
Nacrite Al 2 Si 2 O 5 ( OH ) 4 is a clay mineral that is polymorphous (or polytypic ) with kaolinite . [ 4 ] [ 5 ] It crystallizes in the monoclinic system. X-ray diffraction analysis is required for positive identification.
Nacrite was first described in 1807 for an occurrence in Saxony , Germany . The name is from nacre in reference to the dull luster of the surface of nacrite masses scattering light with slight iridescences resembling those of the mother of pearls secreted by oysters .
This article about materials science is a stub . You can help Wikipedia by expanding it .
This article about a specific silicate mineral is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nacrite |
Nadcap (formerly NADCAP , the National Aerospace and Defense Contractors Accreditation Program) is a global cooperative accreditation program for aerospace engineering , defense and related industries.
The Nadcap program is administered by the Performance Review Institute (PRI). Nadcap was established in 1990 by SAE International . Nadcap's membership consists of "prime contractors" who coordinate with aerospace accredited suppliers to develop industry-wide audit criteria for special processes and products. Through PRI, Nadcap provides independent certification of manufacturing processes for the industry. [ 1 ] PRI has its headquarters in Warrendale, Pennsylvania with branch offices for Nadcap located in London , Beijing , and Nagoya . [ 2 ]
The Nadcap program provides accreditation for special processes in the aerospace and defense industry.
These include:
PRI schedules an audit and assigns an industry approved auditor who will conduct the audit using an industry agreed checklist. At the end of the audit, any non-conformity issues will be raised through a non-conformance report. PRI will administer and close out the non-conformance reports with the Supplier. Upon completion PRI will present the audit pack to a 'special process Task Group’ made up of members from industry who will review it and vote on its acceptability for approval.
The Nadcap subscribers include:
Nadcap meetings are held several times a year in different locations worldwide. For example, the 2017 meetings were held in New Orleans , LA , USA in February, Berlin ( Germany ) in June; and Pittsburgh ( Pennsylvania ). During these meetings there are open Task Group meetings and other workshops (with participation of Primes, Suppliers, and PRI staff). These meetings are used to discuss the program development and changes to audit criteria among other topics. Agendas and minutes are posted on the PRI website. [ 3 ]
During the Nadcap meetings, training classes are provided on different topics such as: | https://en.wikipedia.org/wiki/Nadcap |
The nadir [ a ] [ b ] is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
The direction opposite of the nadir is the zenith .
Although it entered English via other European languages, the word “nadir” is ultimately an Arabic loanword . It comes from the Arabic word “nazir”, meaning “opposite to”. More specifically, it originated from the Arabic phrase “nazir as-samt”, meaning “[the] opposite direction”. [ 2 ]
Hebrew (whether ancient or modern ) is a related language to Arabic, as they are both Semitic languages . [ 3 ] Hebrew also has a word “nadir” (נדיר), but with a somewhat different meaning: it is an adjective meaning “rare”. [ 4 ] However, the same word also has a specialized usage to match its meaning in other languages like English. [ 5 ]
Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous terms. Specifically, in astronomy , geophysics and related sciences (e.g., meteorology ), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location.
The term can also be used to represent the lowest point that a celestial object reaches along its apparent daily path around a given point of observation (i.e. the object's lower culmination ). This can be used to describe the position of the Sun , but it is only technically accurate for one latitude at a time and only possible at the low latitudes . The Sun is said to be at the nadir at a location when it is at the zenith at the location's antipode and is 90° below the horizon.
Nadir also refers to the downward-facing viewing geometry of an orbiting satellite , [ 6 ] such as is employed during remote sensing of the atmosphere , as well as when an astronaut faces the Earth while performing a spacewalk . A nadir image is a satellite image or aerial photo of the Earth taken vertically . A satellite ground track represents its orbit projected to nadir on to Earth's surface.
Generally in medicine, nadir is used to indicate the progression to the lowest point of a clinical symptom (e.g. fever patterns) or a laboratory count. In oncology , the term nadir is used to represent the lowest level of a blood cell count while a patient is undergoing chemotherapy . [ 7 ] A diagnosis of neutropenic nadir after chemotherapy typically lasts 7–10 days. [ 8 ]
The word is also used figuratively to mean a low point, such as with a person's spirits , [ 9 ] the quality of an activity or profession, [ 10 ] or the nadir of American race relations . [ 11 ] | https://en.wikipedia.org/wiki/Nadir |
Nadir and Occultation for MArs Discovery ( NOMAD ) is a 3-channel spectrometer on board the ExoMars Trace Gas Orbiter (TGO) launched to Mars orbit on 14 March 2016.
NOMAD is designed to perform high-sensitivity orbital identification of atmospheric components, concentration and temperature, their sources, loss, and cycles. It measures the sunlight reflected from the surface and atmosphere of Mars, and it analyses its wavelength spectrum to identify the components of the Martian atmosphere that may suggest a biological source . The Principal Investigator is Ann Carine Vandaele, from the Belgian Institute for Space Aeronomy , Belgium.
NOMAD is one of four science instruments on board the European ExoMars TGO orbiter. This spectrometer consists of three separate channels: solar occultation (SO), limb nadir and occultation (LNO), and ultraviolet and visible spectrometer (UVIS). The first two channels work in the infrared (2.2 to 4.3 μm); the third channel (UVIS) works in the UV-visible range (0.2 to 0.65 μm), which is able to measure ozone , sulphuric acid , and perform aerosol studies. [ 5 ] [ 6 ] Measurements are carried out during solar occultation , i.e. the instrument points toward the sunset as the orbiter moves toward or away the dark side of Mars. It also measures in nadir mode, i.e. looking directly at the sunlight reflected from the surface and atmosphere of Mars. [ 6 ] [ 7 ]
Since 9 April 2018, [ 3 ] NOMAD is measuring the existing atmospheric concentrations of gases, their temperature and total densities. [ 8 ] Atmospheric methane concentrations below 1 ppb can be detected. [ 8 ] [ 9 ] [ 10 ] These measurements will also facilitate investigations in the production and loss processes for the cycles of water , carbon, and dust. [ 8 ]
NOMAD development and fabrication was carried out by OIP Sensor Systems at Belgium, in collaboration with partners in Spain, the United Kingdom, Italy, US, and Canada. [ 5 ] [ 6 ] Its development was based on the SPICAV spectrometer flown on Venus Express . [ 10 ]
NOMAD will map the composition and distribution of Mars' atmospheric trace gases and isotopes in unprecedented detail. The specific objectives are: [ 11 ]
To achieve these objectives, NOMAD covers a spectral region from UV, visible, and infrared that reveals the signatures of the following molecules and isotopologues:
CO 2 (including 13 CO 2 , 17 OCO, 18 OCO, C 18 O 2 ), CO (including 13 CO, C 18 O), H 2 O (including HDO ), NO 2 , N 2 O, O 3 , CH 4 (including 13 CH 4 , CH 3 D), C 2 H 2 , C 2 H 4 , C 2 H 6 , H 2 CO, HCN, OCS, SO 2 , HCl, HO 2 , and H 2 S. [ 8 ]
In particular, the detection of the different methane (CH 4 ) isotopologues ( 13 CH 4 , CH 3 D) will be key to help determine whether they are of geological ( serpentinisation , clathrates ) or a biological source. [ 8 ] In addition, NOMAD can detect formaldehyde ( H 2 CO ) which is a photochemical product of methane, as well as nitrous oxide ( N 2 O ) and hydrogen sulfide ( H 2 S ) which are potential atmospheric biosignatures . [ 8 ] SO 2 , a gas related to volcanism may reveal present or recent volcanic activity on Mars . [ 8 ] | https://en.wikipedia.org/wiki/Nadir_and_Occultation_for_Mars_Discovery |
In differential geometry , a Nadirashvili surface is an immersed complete bounded minimal surface in R 3 with negative curvature. The first example of such a surface was constructed by Nikolai Nadirashvili [ de ] in Nadirashvili (1996) . This simultaneously answered a question of Hadamard about whether there was an immersed complete bounded surface in R 3 with negative curvature, and a question of Eugenio Calabi and Shing-Tung Yau about whether there was an immersed complete bounded minimal surface in R 3 .
Hilbert (1901) harvtxt error: no target: CITEREFHilbert1901 ( help ) showed that a complete immersed surface in R 3 cannot have constant negative curvature, and Efimov (1963) show that the curvature cannot be bounded above by a negative constant. So Nadirashvili's surface necessarily has points where the curvature is arbitrarily close to 0. | https://en.wikipedia.org/wiki/Nadirashvili_surface |
Naegleria gruberi is a species of Naegleria . It is famous for its ability to change from an amoeba , which lacks a cytoplasmic microtubule cytoskeleton , to a flagellate , which has an elaborate microtubule cytoskeleton, including flagella. This "transformation" includes de novo synthesis of basal bodies (or centrioles).
It was first characterized in 1899, [ 1 ] and the genome sequence published in 2010. [ 2 ] [ 3 ]
Naegleria gruberi is a non-pathogenic biosafety level 1 organism, although it is related to the deadly Naegleria fowleri . [ 4 ]
Naegleria gruberi is a free-living organism that can be extracted from wet soil and freshwater [ 2 ] The strain NEG-M is the only Naegleria species that has a fully sequenced genome. Naegleria belongs to the Jakobids, Euglenozoans, and Heteroloboseans (JEH) group. The Naegleria genome sequence has indicated that the amoeboflagellate contains actin and microtubule cytoskeletons, mitotic and meiotic machinery, and several transcription factors. Naegleria' s mitochondrial genome encodes some components of a mitochondrial c and c1 maturation system. [ 5 ] [ 6 ]
Naegleria's mitochondria resemble the evolutionary intermediate thought to have occurred within the ancestor of all eukaryotes, because of its presence of mitochondrial Fe-hydrogenase and complete aerobic respiration system. The Naegleria genome is able to oxidize glucose, various amino acids and fatty acids through the Krebs cycle. [ 5 ]
The ancestor of existing eukaryotes have been thought to contain a fair number of introns. Nearly 36% of Naegleria genes are assumed to contain at least one intron and 17% contain multiple introns. The position of the introns are conserved, indicating that they are ancient. [ 5 ]
Naegleria amoeba undergo a closed mitosis, in which the nuclear envelope doesn't break down, but still proceeds through the typical stages. The multitubulin hypothesis predicts that eukaryotes contain multiple tublin genes with distinct properties. Naegleria uses different tubulins for mitosis and flagellar assembly. [ 5 ]
Observations suggest that Naegleria is primarily an asexual organism that reproduces by division of its amoebae to produce substantial clonal populations. However, analysis of the genome strain NEG-M revealed that it is a composite of two distinct haplotypes having arisen from an interbreeding population. Therefore, Naegleria is likely to be able to undergo genetic exchange. The NEG-M strain is the heterozygous result of a past mating of two strains, and it appears genetically equipped to mate again. However, further studies still need to be performed. [ 5 ] | https://en.wikipedia.org/wiki/Naegleria_gruberi |
Naenara is a North Korean intranet web browser software developed by the Korea Computer Center for use of the national Kwangmyong intranet. It is developed from a version of Mozilla Firefox and is distributed with the Linux -based operating system Red Star OS that North Korea developed due to licensing and security issues with Microsoft Windows . [ 3 ]
Naenara is a modified version of Mozilla Firefox . [ 4 ] Red Star OS and Naenara were developed by the Korea Computer Center that states on its web page that it seeks to develop Linux-based software for use. [ 5 ]
Naenara can be used to browse approximately 1,000 to 5,500 websites in the national Kwangmyong intranet. [ 6 ]
When Naenara is run, it tries to contact an IP address at http://10.76.1.11/ . [ 1 ] The default search engine for the browser is Google Korea. [ 3 ]
This Internet-related article is a stub . You can help Wikipedia by expanding it .
This North Korea -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Naenara_(browser) |
Nafion is a brand name for a sulfonated tetrafluoroethylene based fluoropolymer - copolymer synthesized in 1962 by Dr. Donald J. Connolly at the DuPont Experimental Station in Wilmington Delaware (U.S. Patent 3,282,875). Additional work on the polymer family was performed in the late 1960s by Dr. Walther Grot of DuPont . [ 1 ] Nafion is a brand of the Chemours company. It is the first of a class of synthetic polymers with ionic properties that are called ionomers . Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene ( PTFE ) backbone. [ 2 ] [ 3 ] [ 4 ] Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent chemical and mechanical stability in the harsh conditions of this application.
The chemical basis of Nafion's ion-conductive properties remain a focus of extensive research. [ 2 ] Ion conductivity of Nafion increases with the level of hydration. Exposure of Nafion to a humidified environment or liquid water increases the amount of water molecules associated with each sulfonic acid group. The hydrophilic nature of the ionic groups attract water molecules, which begin to solvate the ionic groups and dissociate the protons from the -SO 3 H ( sulfonic acid ) group. The dissociated protons "hop" from one acid site to another through mechanisms facilitated by the water molecules and hydrogen bonding . [ 2 ] Upon hydration, Nafion phase-separates at nanometer length scales resulting in formation of an interconnected network of hydrophilic domains which allow movement of water and cations , but the membranes do not conduct electrons and minimally conduct anions due to permselectivity (charge-based exclusion). Nafion can be manufactured with or exchanged to alternate cation forms for different applications (e.g. lithiated for Li-ion batteries) and at different equivalent weights (EWs), alternatively considered as ion-exchange capacities (IECs), to achieve a range of cationic conductivities with trade-offs to other physicochemical properties such as water uptake and swelling.
Nafion can be produced as both a powder resin and a copolymer . It has various chemical configurations and thus several chemical names in the IUPAC system. Nafion-H, for example, includes the following systematic names:
The molecular weight of Nafion is variable due to differences in processing and solution morphology. [ 3 ] [ 4 ] The structure of a Nafion unit illustrates the variability of the material; for example, the most basic monomer contains chain variation between the ether groups (the z subscript). Conventional methods of determining molecular weight such as light scattering and gel permeation chromatography are not applicable because Nafion is insoluble, although the molecular weight has been estimated at 10 5 –10 6 Da. [ 3 ] [ 4 ] Instead, the equivalent weight (EW) and material thickness are used to describe most commercially available membranes. The EW is the number of grams of dry Nafion per mole of sulfonic acid groups when the material is in the acid form. [ 4 ] Nafion membranes are commonly categorized in terms of their EW and thickness. [ 2 ] [ 5 ] For example, Nafion 117 indicates an extrusion-cast membrane with 1100 g/mol EW and 0.007 inches (7 thou) in thickness. [ 5 ] In contrast to equivalent weight, conventional ion-exchange resins are usually described in terms of their ion exchange capacity (IEC), which is the multiplicative inverse or reciprocal of the equivalent weight, i.e., IEC = 1000/EW.
Nafion derivatives are first synthesized by the copolymerization of tetrafluoroethylene (TFE) (the monomer in Teflon) and a derivative of a perfluoro (alkyl vinyl ether) with sulfonyl acid fluoride. The latter reagent can be prepared by the pyrolysis of its respective oxide or carboxylic acid to give the olefinated structure. [ 6 ]
The resulting product is an -SO 2 F-containing thermoplastic that is extruded into films. Hot aqueous NaOH converts these sulfonyl fluoride (-SO 2 F) groups into sulfonate groups (-SO 3 − Na + ). This form of Nafion, referred to as the neutral or salt form, is finally converted to the acid form containing the sulfonic acid (-SO 3 H) groups. Nafion can be dispersed into solution by heating in aqueous alcohol at 250 °C in an autoclave for subsequent casting into thin films or use as polymeric binder in electrodes. By this process, Nafion can be used to generate composite films, coat electrodes , or repair damaged membranes. [ 3 ]
The combination of the stable PTFE backbone with the acidic sulfonic groups gives Nafion its characteristics: [ 2 ] [ 7 ]
The morphology of Nafion membranes is a matter of continuing study to allow for greater control of its properties. Other properties such as water management, hydration stability at high temperatures, electro-osmotic drag , as well as the mechanical, thermal, and oxidative stability, are affected by the Nafion structure. A number of models have been proposed for the morphology of Nafion to explain its unique transport properties. [ 2 ]
The first model for Nafion, called the cluster-channel or cluster-network model , consisted of an equal distribution of sulfonate ion clusters (also described as 'inverted micelles ' [ 4 ] ) with a 40 Å (4 nm ) diameter held within a continuous fluorocarbon lattice. Narrow channels about 10 Å (1 nm) in diameter interconnect the clusters, which explains the transport properties. [ 3 ] [ 4 ] [ 12 ]
The difficulty in determining the exact structure of Nafion stems from inconsistent solubility and crystalline structure among its various derivatives. Advanced morphological models have included a core-shell model where the ion-rich core is surrounded by an ion poor shell, a rod model where the sulfonic groups arrange into crystal-like rods, and a sandwich model where the polymer forms two layers whose sulfonic groups attract across an aqueous layer where transport occurs. [ 4 ] Consistency between the models include a network of ionic clusters; the models differ in the cluster geometry and distribution. Although no model has yet been determined fully correct, some scientists have demonstrated that as the membrane hydrates, Nafion's morphology transforms from the cluster-channel model to a rod-like model. [ 4 ]
A cylindrical-water channel model [ 13 ] was also proposed based on simulations of small-angle X-ray scattering data and solid state nuclear magnetic resonance studies. In this model, the sulfonic acid functional groups self-organize into arrays of hydrophilic water channels, each ~ 2.5 nm in diameter, through which small ions can be easily transported. Interspersed between the hydrophilic channels are hydrophobic polymer backbones that provide the observed mechanical stability. Many recent studies, however, favored a phase-separated nanostructure consisting of locally-flat, or ribbon-like, hydrophilic domains based on evidence from direct-imaging studies [ 14 ] and more comprehensive analysis of the structure and transport properties. [ 2 ] [ 15 ]
Nafion's properties make it suitable for a broad range of applications. Nafion has found use in fuel cells , electrochemical devices, chlor-alkali production, metal-ion recovery, water electrolysis , plating , surface treatment of metals, batteries, sensors , Donnan dialysis cells , drug release, gas drying or humidification, and superacid catalysis for the production of fine chemicals. [ 3 ] [ 4 ] [ 7 ] [ 16 ] Nafion is also often cited for theoretical potential (i.e., thus far untested) in a number of fields. With consideration of Nafion's wide functionality, only the most significant will be discussed below.
Chlorine and sodium/potassium hydroxide are among the most produced commodity chemicals in the world. Modern production methods produce Cl 2 and NaOH/KOH from the electrolysis of brine using a Nafion membrane between half-cells. Before the use of Nafion, industries used mercury containing sodium amalgam to separate sodium metal from cells or asbestos diaphragms to allow for transfer of sodium ions between half cells; both technologies were developed in the latter half of the 19th century. The disadvantages of these systems is worker safety and environmental concerns associated with mercury and asbestos, economical factors also played a part, and in the diaphragm process chloride contamination of the hydroxide product. Nafion was the direct result of the chlor-alkali industry addressing these concerns; Nafion could tolerate the high temperatures, high electrical currents, and corrosive environment of the electrolytic cells. [ 3 ] [ 4 ] [ 7 ]
The figure to the right shows a chlor-alkali cell where Nafion functions as a membrane between half cells. The membrane allows sodium ions to transfer from one cell to the other with minimal electrical resistance. The membrane was also reinforced with additional membranes to prevent gas product mixing and minimize back transfer of Cl − and − OH ions. [ 3 ]
Although fuel cells have been used since the 1960s as power supplies for satellites, recently they have received renewed attention for their potential to efficiently produce clean energy from hydrogen. Nafion was found effective as a membrane for proton exchange membrane (PEM) fuel cells by permitting hydrogen ion transport while preventing electron conduction. Solid Polymer Electrolytes, which are made by connecting or depositing electrodes (usually noble metal) to both sides of the membrane, conduct the electrons through an energy requiring process and rejoin the hydrogen ions to react with oxygen and produce water. [ 3 ] Fuel cells are expected to find strong use in the transportation industry.
Nafion, as a superacid , has potential as a catalyst for organic synthesis . Studies have demonstrated catalytic properties in alkylation , isomerization , oligomerization , acylation , ketalization , esterification , hydrolysis of sugars and ethers , and oxidation . New applications are constantly being discovered. [ 16 ] These processes, however, have not yet found strong commercial use. Several examples are shown below:
Nafion-H gives efficient conversion whereas the alternative method, which employs Friedel-Crafts synthesis , can promote polyalkylation: [ 17 ]
The amount of Nafion-H needed to catalyze the acylation of benzene with aroyl chloride is 10–30% less than the Friedel-Crafts catalyst: [ 17 ]
Nafion-H increases reaction rates of protection via dihydropyran or o-trialkylsilation of alcohols, phenol, and carboxylic acids. [ 16 ]
Nafion can catalyze a 1,2-hydride shift . [ 16 ]
It is possible to immobilize enzymes within the Nafion by enlarging pores with lipophilic salts. Nafion maintains a structure and pH to provide a stable environment for the enzymes. Applications include catalytic oxidation of adenine dinucleotides . [ 16 ]
Nafion has found use in the production of sensors , with application in ion-selective, metallized, optical, and biosensors . What makes Nafion especially interesting is its demonstration in biocompatibility . Nafion has been shown to be stable in cell cultures as well as the human body, and there is considerable research towards the production of higher sensitivity glucose sensors. [ 3 ]
Nafion surfaces show an exclusion zone against bacteria colonization. [ 18 ] Moreover, layer-by-layer coatings comprising Nafion show excellent antimicrobial properties. [ 19 ]
The SpaceX Dragon 2 human-rated spacecraft uses Nafion membranes to dehumidify the cabin air. One side of the membrane is exposed to the cabin atmosphere, the other to the vacuum of space. This results in dehumidification since Nafion is permeable to water molecules but not air. This saves power and complexity since cooling is not required (as needed with a condensing dehumidifier), and the removed water is rejected to space with no additional mechanism needed. [ 20 ]
Normal Nafion will dehydrate (thus lose proton conductivity) when the temperature is above ~80 °C. This limitation troubles the design of fuel cells because higher temperatures are desirable for better efficiency and CO tolerance of the platinum catalyst. Silica and zirconium phosphate can be incorporated into Nafion water channels through in situ chemical reactions to increase the working temperature to above 100 °C. [ citation needed ] | https://en.wikipedia.org/wiki/Nafion |
Nafovanny in Vietnam is the largest captive-breeding primate facility in the world. It supplies crab-eating Macaques ( Macaca fascicularis ) to animal testing laboratories.
Nafovanny was set up in 1994 by Vanny Chian Technology, a Hong Kong company, according to Reuters . [ 2 ]
Criticism of the project was expressed by Dr. John Wedderburn, a former member of the RSPCA 's ruling council: "It is terrible, terrible. There is no end to the ingenuity of man when it comes to making money and being cruel." Daniel Chen, a director of Vanny Chain Technology responded "We have not got a problem with that because what we are doing is very humane and it is for the welfare of human beings." [ 2 ]
Nafovanny consists of two main farms in Long Thanh , Vietnam. [ 3 ] According to the British Union for the Abolition of Vivisection (BUAV), the facility also maintains satellite breeding farms on the Cambodian border, in which the BUAV alleges wild monkeys may also be held. The existence of these farms is not referenced in the company's brochure, according to the BUAV. [ 4 ]
The British Home Office has said it has no knowledge of Nafovanny satellite farms. However, it also said that "This decision was premised upon the contractual arrangements having been entered into in good-faith whilst Nafovanny was still considered to be an acceptable source, and animals already selected for onward supply to the UK. The view was taken that proper provision would be made for the welfare of these animals prior to their being shipped to the UK – and that this could be verified from the records and findings on arrival." [ 5 ]
The British government approved Nafovanny to export primates to British laboratories in 1999. [ 4 ] The British Animal Scientific Procedures Inspectorate visited Nafovanny in March 2005 and identified "shortcomings in animal accommodation and care", but since then, the government has "received assurances and evidence that significant improvements have been made". [ 6 ]
According to Viet Nam News , 3,000 Nafovanny macaques were exported to the U.S. for testing purposes in 2000. [ 7 ] The International Primate Protection League reported that Nafovanny exported 1,440 macaques to the United States in 2013. [ 8 ] | https://en.wikipedia.org/wiki/Nafovanny |
Naftalan or Naphtalan is a type of crude oil . It is named after Naftalan, Azerbaijan , where it is found. It is known for its use in alternative medicine .
Naftalan crude oil is too heavy for normal export uses (unlike Azerbaijan's plentiful Caspian Sea oil): it contains about 50 percent cycloalkanes (naphthenic hydrocarbons). [ 1 ]
In Azerbaijan, people using the oil generally sit in a bath and are covered in oil up to their necks. There are numerous petroleum spas in the city of Naftalan itself. [ 2 ] [ 3 ] As a result, it has become a destination for health tourism . [ 4 ]
Naftalan oil has been used since antiquity and was noted by Marco Polo . [ 5 ] Its chemistry has been studied from the 1870s. [ 6 ] Treatment centres were established in Azerbaijan and were visited by people from the Soviet Union . [ 7 ] Its therapeutic effects have been studied since the 1890s. [ 8 ]
After the oil boom at the turn of the 20th century, the Baku naftalan started to be extracted in higher volumes, and exported to Germany. [ 9 ] [ 10 ] After the borders were closed following the 1917 Russian Revolution , it fell into oblivion in the West . It still attracted some attention in the Soviet Union, when the Azerbaijan Medical University opened a small health resort that was in full operation by 1936. [ 7 ] [ 9 ] [ 11 ] In the 1930s, academician T. G. Pashayev started to try to isolate naphthalan from industrial paraffin and naphthenic oils and proposed the term, though more current research indicates that the term "earth mineral oil" is more appropriate for what he described in his paper published in Moscow in 1959. [ 12 ]
During the 20th century, a large number of academic papers were published by Soviet researchers about the topic. [ 13 ] Nevertheless, in Europe the results from the Naphthalan Health Resort in Azerbaijan were largely rejected because the idea of the application of native oil to human subjects was not acceptable. [ 14 ]
In the 1970s, the School of Medicine, University of Zagreb conducted its own research to compare the kinds of oil found near Baku and near Križ , Croatia . After two years, in 1978, they concluded that the oil they analyzed was not carcinogenic, after testing at INA labs and at the Ruđer Bošković Institute , and conducting a trial with 770 patients. [ 13 ] In 1989 the Naftalan Special Hospital for Medical Rehabilitation was founded in Ivanić Grad . [ 13 ] Their use of naphtalan oil is restricted to a refined distillate, devoid of tar, aromatic content and other undesired substances, in an effort to minimize the rate of contraindications and side effects. [ 14 ] This hospital later conducted a 10-year follow-up and observation of 10,000 of their patients and respective associated data, and reportedly observed a number of therapeutic effects. [ 15 ]
As recently as 2006, the New York Times published an article referring to naftalan as mostly naphthalene , which would be carcinogenic to humans. [ 2 ] In 2009, The Independent described one of the spas, repeating the claim about the composition of the oil. [ 16 ]
Naftalan oil is a type of heavy crude oil , a dense and viscous mixture with components including aromatics , naphthenes , asphaltenes and resins . [ 1 ] In particular it contains naphthenic acids , an oil industry term for a group of carboxylic acids which can be up to 3 percent of the oil by weight. [ 17 ] [ 18 ] Purified oil used in some treatments contains mainly polycyclic hydrocarbons, with the most pure having a transparent white to lemon-yellow color and napthenic content up to 98.5 percent. [ 19 ] [ 20 ]
Early studies of the oil's chemistry and therapeutic properties involved partially purified material, a naptha used as an ointment which was compared favourably to Vaseline . It was applied to wounds and burns. [ 21 ]
Spas in Naftalan, Azerbaijan use the crude oil for whole-body bathing, [ 3 ] [ 7 ] a procedure which has been described by the British documentary photographer Chloe Dewe Mathews . [ 22 ] [ 23 ] A typical single bathing session lasts ten minutes. [ 24 ] Health tourism is now a major industry in Azerbaijan. [ 4 ]
The purified oil, which is a mixture of cycloalkanes , is used in combination with mineral waters for balneotherapy . [ 19 ] : 206 [ 20 ]
The concept of using heavy crude oil in spa treatments has led to a Canadian proposal to create a "bitumen spa" on the same principles as the Naftalan ones. [ 25 ] | https://en.wikipedia.org/wiki/Naftalan_oil |
Naga fireballs ( Thai : บั้งไฟพญานาค ; RTGS : bang fai phaya nak ), also known as bung fai phaya nak or "Mekong lights" and formerly "ghost lights", [ 1 ] are a phenomenon said to be seen annually on the Mekong River . Glowing balls are alleged to naturally rise from the water high into the air. [ 2 ] The balls are said to be reddish and to range in size from smaller sparkles up to the size of basketballs. They quickly rise up to a couple of hundred metres before disappearing. The number of fireballs reported varies between tens and thousands per night. [ 3 ] The phenomenon is locally attributed to phaya nak , a giant serpent ( Nāga ) said to live in the Mekong. [ 1 ]
The fireballs are most often reported around the night of Wan Ok Phansa at the end of Buddhist Lent in late-October. [ 3 ] Naga fireballs have been reported over an approximately 250 km (160 mi) long section of the Mekong River centered approximately on Phon Phisai in the Phon Phisai District . Fireballs have also been reported rising from smaller rivers, lakes and ponds in the region. The fireballs were called "ghost lights" by locals until the mid-1980s, when the local council officially named them "phaya nak lights". In 2018, one observer noted that while the light phenomenon is "hundreds of years old", the new name Phaya Nak lights is only about 35 years old." [ 1 ] [ 4 ]
Although the fireballs are regularly seen on the river during the Phayanak Festival, a 2002 iTV documentary showed Lao soldiers firing tracer rounds into the air across the river from the festival. Skeptic Brian Dunning suggests that it would be impossible for anyone across the half-mile river to hear a gunshot because it would take 2.5 seconds for the sound to travel to the spectators, and by then the crowd watching would have already noticed the light and started cheering, drowning out any sound to reach them. [ 5 ] Thai biologist Jessada Denduangboripant analysed footage of a Naga fireball event and concluded that the effect was caused by the firing of flare guns from the other side of the river. [ 6 ] [ 7 ] A 2021 official investigation by Lao authorities during a COVID-19 lockdown and curfew, concluded "In response to the news in foreign media, I would like to state that it is extremely unlikely that anyone could have fired weapons or flare ammunition without our knowledge on that night. We ensured a heavy police presence through the night and did not encounter any incidents". [ 8 ]
Some individuals have attempted to explain the phenomenon scientifically. One explanation is that the fireball is a result of flammable phosphine gas generated by the marshy environment. [ 9 ] Dunning writes that such fireballs are very unlikely to spontaneously ignite, and would not stay lit when at the speeds the fireballs travel, and that there is no science that can explain "the Naga Fireballs to be naturally produced burning gas bubbles." [ 5 ]
A similar explanation involves a phenomenon seen in plasma physics : free-floating plasma orbs [ 10 ] created when surface electricity (e.g., from a capacitor) is discharged into a solution. However, these are produced under controlled conditions during plasma ball experiments using high voltage capacitors, microwave oscillators, or microwave ovens , rather than naturally occurring. [ 11 ] [ 12 ] | https://en.wikipedia.org/wiki/Naga_fireball |
In algebra , Nagata's conjecture states that Nagata's automorphism of the polynomial ring k [ x , y , z ] is wild . The conjecture was proposed by Nagata ( 1972 ) and proved by Ualbai U. Umirbaev and Ivan P. Shestakov ( 2004 ).
Nagata's automorphism is given by
where Δ = x z + y 2 {\displaystyle \Delta =xz+y^{2}} .
For the inverse, let ( a , b , c ) = ϕ ( x , y , z ) {\displaystyle (a,b,c)=\phi (x,y,z)} Then z = c {\displaystyle z=c} and Δ = b 2 + a c {\displaystyle \Delta =b^{2}+ac} .
With this y = b − Δ c {\displaystyle y=b-\Delta c} and x = a + 2 Δ y + Δ 2 z {\displaystyle x=a+2\Delta y+\Delta ^{2}z} . | https://en.wikipedia.org/wiki/Nagata's_conjecture |
In topology , the Nagata–Smirnov metrization theorem characterizes when a topological space is metrizable . The theorem states that a topological space X {\displaystyle X} is metrizable if and only if it is regular , Hausdorff and has a countably locally finite (that is, 𝜎-locally finite) basis .
A topological space X {\displaystyle X} is called a regular space if every non-empty closed subset C {\displaystyle C} of X {\displaystyle X} and a point p not contained in C {\displaystyle C} admit non-overlapping open neighborhoods.
A collection in a space X {\displaystyle X} is countably locally finite (or 𝜎-locally finite) if it is the union of a countable family of locally finite collections of subsets of X . {\displaystyle X.}
Unlike Urysohn's metrization theorem , which provides only a sufficient condition for metrizability, this theorem provides both a necessary and sufficient condition for a topological space to be metrizable. The theorem is named after Junichi Nagata and Yuriĭ Mikhaĭlovich Smirnov , whose (independent) proofs were published in 1950 [ 1 ] and 1951, [ 2 ] respectively.
This topology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nagata–Smirnov_metrization_theorem |
In mathematics , the Nagell–Lutz theorem is a result in the diophantine geometry of elliptic curves , which describes rational torsion points on elliptic curves over the integers. It is named for Trygve Nagell and Élisabeth Lutz .
Suppose that the equation
defines a non-singular cubic curve E with integer coefficients a , b , c , and let D be the discriminant of the cubic polynomial on the right side:
If P = ( x , y ) {\displaystyle P=(x,y)} is a rational point of finite order on E , for the elliptic curve group law , then:
The Nagell–Lutz theorem generalizes to arbitrary number fields and more
general cubic equations. [ 1 ] For curves over the rationals, the generalization says that, for a nonsingular cubic curve whose Weierstrass form
has integer coefficients, any rational point P = ( x , y ) {\displaystyle P=(x,y)} of finite
order must have integer coordinates, or else have order 2 and
coordinates of the form x = m / 4 {\displaystyle x=m/4} , y = n / 8 {\displaystyle y=n/8} , for m and n integers.
The result is named for its two independent discoverers, the Norwegian Trygve Nagell (1895–1988) who published it in 1935, and Élisabeth Lutz (1937). | https://en.wikipedia.org/wiki/Nagell–Lutz_theorem |
The Nagel–Schreckenberg model is a theoretical model for the simulation of freeway traffic. The model was developed in the early 1990s by the German physicists Kai Nagel and Michael Schreckenberg. [ 1 ] It is essentially a simple cellular automaton model for road traffic flow that can reproduce traffic jams, i.e., show a slow down in average car speed when the road is crowded (high density of cars). The model shows how traffic jams can be thought of as an emergent or collective phenomenon due to interactions between cars on the road, when the density of cars is high and so cars are close to each other on average.
In the Nagel–Schreckenberg model, a road is divided into cells . In the original model, these cells are aligned in a single row whose ends are connected so that all cells make up a circle (this is an example of what are called periodic boundary conditions ). Each cell is either empty road or contains a single car; i.e., no more than one car can occupy a cell at any time. Each car is assigned a velocity which is an integer between 0 and a maximum velocity (= 5 in Nagel and Schreckenberg's original work).
Time is discretized into time steps. This discretization in both space and time results in a cellular automaton. One can think of a cell as being a few car lengths long and the maximum velocity as being the speed limit on the road. The time step is then the time taken for a car at the speed limit to travel around 10 car lengths. However, the model can also be thought as just a way to understand or to model features of traffic jams by showing how interactions between nearby cars cause the cars to slow down. In each time step, the procedure is as follows. [ 1 ]
In each step, the following four actions are conducted in order from first to last, and all are applied to all cars. In each action the updates are applied to all cars in parallel.
These four actions are repeated many times, as long as is required to study any traffic jams that may form. The model is an example of a cellular automaton . The model is for a single lane where cars cannot pass each other; there is no overtaking.
Above and to the right is a plot of the average velocity as a function of the density of cars, obtained from a simulation of the original Nagel–Schreckenberg model. [ 1 ] In the deterministic limit, p = 0, the velocity is constant at the maximum velocity (here 5) up to a density ρ = 1/(maximum velocity + 1) = 1 / 6 = 0.167, at which point there is a discontinuity in the slope due to the sudden appearance of traffic jams. Then as the density increases further, the average velocity decreases until it reaches zero when the road is 100% occupied. When p = 0.3, and so there are random decreases in velocity, then at low densities the average velocity is of course slower. However, note p > 0 also shifts the density at which jams appear to lower densities – traffic jams appear at the knee in the curve which for p = 0.3 is close to 0.15, and the random decelerations round off the discontinuity in the slope found for p = 0 at the onset of traffic jams. [ 2 ]
To the right is the result of an example simulation run of the Nagel–Schreckenberg model, with maximum velocity 5, density of cars 0.35 and probability of deceleration p = 0.3. It is a road of 100 cells. Cars are shown as black dots, and so, for example, if the road had a single car on it the plot would be white except for a single black line of slope −1/5 (maximum velocity = 5). The lines have slopes that are steeper, indicating that jamming is slowing the cars down. Small traffic jams show up as dark bands, i.e., groups of cars that are nose-to-tail and moving slowly to the right. The rippling of the bands is due to the randomization step.
So, the Nagel–Schreckenberg model includes the effect of cars getting in each other's way and so slowing each other down. The average velocity at this density is a little over 1, while at low density it is a little less than the maximum velocity of 5. It also shows that this is a collective phenomenon in which cars bunch up into traffic jams. When jamming occurs the distribution of cars along the road becomes highly non-uniform.
Without the randomization step (third action), the model is a deterministic algorithm , i.e., the cars always move in a set pattern once the original state of the road is set. With randomization this is not the case, as it is on a real road with human drivers. Randomization has the effect of rounding off an otherwise sharp transition. [ 2 ] Just below this transition, one car braking due to a random slow can slow down the cars behind, spontaneously creating a jam. This feature of one car braking at random and causing a jam is absent in a deterministic model. | https://en.wikipedia.org/wiki/Nagel–Schreckenberg_model |
The Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to the Convention on Biological Diversity , also known as the Nagoya Protocol on Access and Benefit Sharing (ABS) , is a 2010 supplementary agreement to the 1992 Convention on Biological Diversity (CBD). Its aim is the implementation of one of the three objectives of the CBD: the fair and equitable sharing of benefits arising out of the utilization of genetic resources , thereby contributing to the conservation and sustainable use of biodiversity . It sets out obligations for its contracting parties to take measures in relation to access to genetic resources, benefit-sharing and compliance.
The protocol was adopted on 29 October 2010 in Nagoya , Japan, and entered into force on 12 October 2014. As of April 2022 [update] , it has been ratified by 137 parties, which includes 141 UN member states and the European Union .
From a concrete perspective, it gives each country sovereignty rights over its biological resources, making biopiracy illegal. [ 1 ] Concerns have been expressed that the added bureaucracy and legislation could be damaging to the monitoring and collection of biodiversity, to conservation, to the international response to infectious diseases, and to research. [ 2 ] [ 3 ]
The Nagoya Protocol applies to genetic resources that are covered by the CBD, and to the benefits arising from their utilization. The protocol also covers traditional knowledge associated with genetic resources that are covered by the CBD and the benefits arising from its utilization.
Its aim is the implementation of one of the three objectives of the CBD: the fair and equitable sharing of benefits arising out of the utilization of genetic resources, thereby contributing to the conservation and sustainable use of biodiversity . [ 4 ]
The protocol was adopted on 29 October 2010 in Nagoya , Japan, at the tenth meeting of the Conference of the Parties, held from 18 to 29 October 2010 [ 5 ] and entered into force on 12 October 2014.
The parties to the treaty decided in 2016 to consider the inclusion of digital sequence information (DSI) in the Nagoya framework. [ 6 ] The Access and Benefit-Sharing (ABS) method, if applied to DSI, would have greatly disrupted the operations of the International Nucleotide Sequence Database Collaboration , in which all data is free and unrestricted. [ 2 ] The multilateral framework for DSI, established in COP 15 (2022), decouples access from benefit-sharing. [ 7 ]
As of April 2022 [update] , it has been ratified by 137 parties, which includes 136 UN member states and the European Union . [ 8 ]
The Nagoya Protocol sets out obligations for its contracting parties to take measures in relation to access to genetic resources, benefit-sharing and compliance. [ citation needed ]
Domestic-level access measures aim to: [ citation needed ]
Domestic-level benefit-sharing measures aim to provide for the fair and equitable sharing of benefits arising from the utilization of genetic resources with the contracting party providing genetic resources. Utilization includes research and development on the genetic or biochemical composition of genetic resources, as well as subsequent applications and commercialization. Sharing is subject to mutually agreed terms. Benefits may be monetary or non-monetary such as royalties and the sharing of research results. [ citation needed ]
Specific obligations to support compliance with the domestic legislation or regulatory requirements of the contracting party providing genetic resources, and contractual obligations reflected in mutually agreed terms, are a significant innovation of the Nagoya Protocol. [ citation needed ]
Contracting parties are to: [ citation needed ]
The Nagoya Protocol's success will require effective implementation at the domestic level. A range of tools and mechanisms provided by the Nagoya Protocol will assist contracting parties including: [ citation needed ]
Based on a country's self-assessment of national needs and priorities, capacity-building may help to: [ citation needed ]
The European Union has ratified a European Nagoya Protocol regulation to implement the Protocol. [ 1 ]
A growing number of Preferential Trade Agreements (PTAs) include provisions related to access to genetic resources or to the sharing of the benefits that arise out of their utilization. Indeed, some recent trade agreements, originating notably from Latin American countries, provide specific measures designed to facilitate the implementation of the ABS provisions contained in the Nagoya Protocol, including measures related to technical assistance, transparency and dispute settlement. [ 10 ]
However, there are concerns that the added bureaucracy and legislation will, overall, be damaging to the monitoring and collection of biodiversity, to conservation, to the international response to infectious diseases, and to research. [ 11 ] [ 3 ] [ 12 ]
Many scientists have voiced concern over the protocol, fearing the increased red tape will hamper disease prevention and conservation efforts. Developing countries have refused to issue permits for basic biodiversity research unrelated to bioprospecting, even prosecuting the scientist in some cases. [ 2 ] Scientists worry that threats of possible imprisonment of scientists will have a chilling effect on research. [ 11 ] [ 12 ]
Non-commercial biodiversity researchers and institutions such as natural history museums fear maintaining biological reference collections and exchanging material between institutions will become difficult. [ 3 ] Museums have reservations about loaning out to developing countries for fear that the return "transfer" will not be approved. [ 2 ]
The bilateral transfer framework of the Nagoya Protocol also has low throughput. In comparison, the International Treaty on Plant Genetic Resources for Food and Agriculture has a multilateral access/transfer framework via the Standard Material Transfer Agreement, allowing 8500 transfers every week. [ 2 ] This is different from Article 10 of the Nagoya Protocol, which asks for a multilateral benefit-sharing framework, which has been continuously "revisited" without an actual implementation. [ 13 ]
Lack of implementation at the national level was frequently attributed as a major factor behind the failure of Nagoya Protocol. [ 14 ] | https://en.wikipedia.org/wiki/Nagoya_Protocol |
In differential geometry and gauge theory , the Nahm equations are a system of ordinary differential equations introduced by Werner Nahm in the context of the Nahm transform – an alternative to Ward 's twistor construction of monopoles . The Nahm equations are formally analogous to the algebraic equations in the ADHM construction of instantons , where finite order matrices are replaced by differential operators.
Deep study of the Nahm equations was carried out by Nigel Hitchin and Simon Donaldson . Conceptually, the equations arise in the process of infinite-dimensional hyperkähler reduction . They can also be viewed as a dimensional reduction of the anti-self-dual Yang-Mills equations ( Donaldson 1984 ). Among their many applications we can mention: Hitchin's construction of monopoles , where this approach is critical for establishing nonsingularity of monopole solutions ; Donaldson's description of the moduli space of monopoles ; and the existence of hyperkähler structure on coadjoint orbits of complex semisimple Lie groups , proved by ( Kronheimer 1990 ), ( Biquard 1996 ), and ( Kovalev 1996 ).
Let T 1 ( z ) , T 2 ( z ) , T 3 ( z ) {\displaystyle T_{1}(z),T_{2}(z),T_{3}(z)} be three matrix-valued meromorphic functions of a complex variable z {\displaystyle z} . The Nahm equations are a system of matrix differential equations
together with certain analyticity properties, reality conditions, and boundary conditions. The three equations can be written concisely using the Levi-Civita symbol , in the form
More generally, instead of considering N {\displaystyle N} by N {\displaystyle N} matrices, one can consider Nahm's equations with values in a Lie algebra g {\displaystyle g} .
The variable z {\displaystyle z} is restricted to the open interval ( 0 , 2 ) {\displaystyle (0,2)} , and the following conditions are imposed:
There is a natural equivalence between
The Nahm equations can be written in the Lax form as follows. Set
then the system of Nahm equations is equivalent to the Lax equation
As an immediate corollary, we obtain that the spectrum of the matrix A {\displaystyle A} does not depend on z {\displaystyle z} . Therefore, the characteristic equation
which determines the so-called spectral curve in the twistor space T P 1 {\displaystyle TP^{1}} is invariant under the flow in z {\displaystyle z} . | https://en.wikipedia.org/wiki/Nahm_equations |
Nachum Eliezer Rabinovitch ( Hebrew : נַחוּם אֱלִיעֶזֶר רָבִּינוֹבִיץּ׳ ; 30 April 1928 – 6 May 2020), born Norman Louis Rabinovitch , [ 1 ] was a Canadian-Israeli Religious Zionist rabbi and posek . He headed the London School of Jewish Studies from 1971 to 1982, and the hesder yeshiva Birkat Moshe in Ma'ale Adumim from 1982 until his death. [ 2 ] [ 3 ]
Nahum Rabinovitch was born in Montreal , Quebec to Sarah (née Weiner) and Sam Rabinovitch. [ 1 ] After completing an eight-year course of studies under Rabbi Pinchas Hirschsprung , Rabinovitch received semicha from Montreal's Yeshivas Merkaz HaTorah in the city's first rabbinical ordination ceremony. [ 4 ] [ 5 ]
After obtaining an honours degree in commerce from Sir George Williams College , he left for Baltimore to pursue a Master of Science degree in mathematics at Johns Hopkins University . While there, he studied at Yeshivas Ner Yisroel , where he received a second ordination from Rabbi Yaakov Yitzchok Ruderman . [ 3 ]
Between 1955 and 1963, Rabinovitch served as spiritual leader of the Brith Sholom Beth Israel Congregation in Charleston, South Carolina . In this role, he helped establish the city's first Jewish day school , of which he served as principal . [ 6 ] He also held appointments as lecturer in mathematics at the College of Charleston and chaplain to the Sixth Naval District Headquarters . [ 7 ] [ 8 ]
In 1963, he was called to serve as a community rabbi in Toronto , and assumed the pulpit of the Clanton Park Synagogue in Downsview . [ 9 ] He completed a Ph.D. in the philosophy and history of mathematics at the University of Toronto in 1971 under the supervision of Kenneth O. May . [ 10 ] His doctoral thesis, Probability and Statistical Inference in Ancient and Medieval Jewish Literature , was published as a monograph in 1973. [ 11 ]
Rabinovitch was appointed principal of Jews' College in early 1970, [ 12 ] and settled in London that spring. [ 13 ] Notable among his students at the college was Chief Rabbi Lord Jonathan Sacks , [ 14 ] [ 15 ] who has cited Rabinovitch as his primary role model . [ 16 ] Ten years later, he accepted an offer to become rosh yeshiva of Yeshivat Birkat Moshe , a hesder institution in Ma'ale Adumim .
In 2015, together with a group of prominent Israeli rabbis, Rabinovitch established Giyur Kehalacha , an independent beit din offering conversions outside of the Chief Rabbinate. [ 17 ] [ 18 ]
Rabinovitch published Halakhic rulings on various subjects, including organ donation , surrogacy , birth control , army service , Shabbat , and kashrut . [ 19 ] His philosophical approach, influenced by Maimonidean rationalism , emphasized the connection between philosophy and Halakha, between Torah and scientific studies, and between theoretical learning and practical applications. [ 17 ]
Rabinovitch was an authority on the writings of Maimonides, about which he published numerous books and essays. He is perhaps best known for his fourteen-volume Yad Peshuta ( lit. "Outstretched Hand"), an in-depth commentary on Maimonides' Mishneh Torah . [ 20 ] He also authored Melumdei Milḥamah ( lit. "Learned in War"), a collection of responsa dealing with Halakhic issues facing religious members of the Israel Defense Forces . [ 21 ]
Rabinovitch was a religious Zionist , a supporter of the settlement movement , [ 20 ] and a vocal opponent of the Oslo Accords and the Disengagement . [ 22 ] [ 3 ] He was, however, often more liberal in social and religious matters than many in the religious Zionist movement. [ 19 ] In an interview, Rabinovitch said that he backed religious studies for women, and did not see a problem in Halakhic decisions taken by women. [ 23 ] Nonetheless, he signed a letter in 2019 agreeing with the Chief Rabbinate 's opposition to religious Jewish women serving in the IDF. [ 24 ] He also ruled that it is incumbent on Israeli combat medics and doctors to treat and save the lives of Palestinian combatants , even if wounded in the course of attacking Israelis. [ 17 ] Rabinovitch characterized Christianity and Islam positively, as movements that spread monotheism , morality , and messianic hope . [ 17 ] In addition, Rabinovitch differed from many other religious Zionist leaders in that he did not view the State of Israel as a harbinger of the Messiah and argued for greater separation between religion and state in Israel. [ 25 ] Often, his iconoclastic positions were deeply influenced not only by Jewish tradition, but by the core ideas of political liberalism as well. [ 25 ]
In 1995, Rabinovitch was among a group of rabbis accused of indirectly influencing Yigal Amir to assassinate Prime Minister Yitzhak Rabin , having branded Rabin a moser and likened his government to Nazis . [ 26 ] [ 27 ] The previous summer, he had also issued a ruling that Jewish soldiers should disobey any government orders to vacate West Bank army bases. [ 28 ] [ 29 ]
Rabinovitch had six children, including British journalist Dina Rabinovitch (born in 1963), who died in 2007 of breast cancer. [ 30 ] [ 31 ] | https://en.wikipedia.org/wiki/Nahum_Rabinovitch |
Naismith's rule helps with the planning of a walking or hiking expedition by calculating how long it will take to travel the intended route, including any extra time taken when walking uphill. This rule of thumb was devised by William W. Naismith , a Scottish mountaineer , in 1892. [ 1 ] [ 3 ] [ 4 ] A modern version can be formulated as follows:
The original Naismith 's rule from 1892 says that one should allow one hour per three miles on the map and an additional hour per 2000 feet of ascent. [ 1 ] [ 4 ] It is included in the last sentence of his report from a trip. [ 1 ] [ 8 ]
Today it is formulated in many ways. Naismith's 1 h / 3 mi + 1 h / 2000 ft can be replaced by:
The basic rule assumes hikers of reasonable fitness, on typical terrain, and under normal conditions. It does not account for delays, such as extended breaks for rest or sightseeing, or for navigational obstacles. For planning expeditions a team leader may use Naismith's rule in putting together a route card . [ citation needed ]
It is possible to apply adjustments or "corrections" for more challenging terrain, although it cannot be used for scrambling routes. In the grading system used in North America , Naismith's rule applies only to hikes rated Class 1 on the Yosemite Decimal System , and not to Class 2 or higher. [ citation needed ]
In practice, the results of Naismith's rule are usually considered the minimum time necessary to complete a route. [ citation needed ]
When walking in groups, the speed of the slowest person is calculated. [ 13 ]
Naismith's rule appears in UK statute law, although not by name. The Adventure Activities Licensing Regulations apply to providers of various activities including trekking. Part of the definition of trekking is that it is over terrain on which it would take more than 30 minutes to reach a road or refuge (by the quickest safe route), based on a walking speed of 5 kilometres per hour plus an additional minute for every 10 metres of ascent. [ 14 ]
Alternatively, the rule can be used to determine the equivalent flat distance of a route. This is achieved by recognising that Naismith's rule implies an equivalence between distance and climb in time terms: 3 miles (=15,840 feet) of distance is equivalent in time terms to 2000 feet of climb. [ 17 ]
Professor Philip Scarf, Associate Dean of Research and Innovation and Professor of Applied Statistics at the University of Salford , [ 18 ] in research published in 2008, gives the following formula: [ 4 ]
where:
That is, 7.92 units of distance are equivalent to 1 unit of climb. For convenience an 8 to 1 rule can be used. So, for example, if a route is 20 kilometres (12 mi) with 1600 metres of climb (as is the case on leg 1 of the Bob Graham Round , Keswick to Threlkeld), the equivalent flat distance of this route is 20+(1.6×8)=32.8 kilometres (20.4 mi). Assuming an individual can maintain a speed on the flat of 5 km/h, the route will take 6 hours and 34 minutes. The simplicity of this approach is that the time taken can be easily adjusted for an individual's own (chosen) speed on the flat; at 8 km/h (flat speed) the route will take 4 hours and 6 minutes. The rule has been tested on fell running times and found to be reliable. [ 17 ] Scarf proposed this equivalence in 1998. [ 4 ] [ 6 ]
As you can see, the Scarf's assumption allows also to calculate the time for each speed, not just one as in case of the original Naismith rule.
Pace is the reciprocal of speed. It can be calculated here from the following formula: [ 6 ] [ 19 ]
where:
This formula is true for m≥0 (uphill or flat terrain). [ 6 ] [ 19 ] It assumes equivalence of distance and climb by applying mentioned earlier α factor. [ 4 ] [ 19 ]
Sample calculations: p0 = 12 min / km (for 5 km / h speed), m = 0.6 km climb / 5 km distance = 0.12, p = 12 · (1 + 7.92 · 0.12) = 23.4 min / km.
Over the years several adjustments have been formulated in an attempt to make the rule more accurate by accounting for further variables such as load carried, roughness of terrain, descents and fitness (or lack of it). The accuracy of some corrections is disputed, [ 20 ] in particular the speed at which walkers descend a gentle gradient . No simple formula can encompass the full diversity of mountain conditions and individual abilities.
Tranter's corrections make adjustments for fitness and fatigue. Fitness is determined by the time it takes to climb 1000 feet over a distance of ½ mile (800 m). Additional adjustments for uneven or unstable terrain or conditions can be estimated by dropping one or more fitness levels.
For example, if Naismith's rule estimates a journey time of 9 hours and your fitness level is 25, you should allow 11.5 hours.
Aitken (1977) assumes that 1 h takes to cover 3 mi (5 km) on paths, tracks and roads, while this is reduced to 2½ mi (4 km) on all other surfaces. [ 5 ]
For both distances he gives an additional 1 h per 2000 ft (600 m) of ascent. [ 5 ] So Aitken doesn't take into account equivalence between distance and climb (proposed by Scarf in 1998 [ 4 ] [ 6 ] ).
Langmuir (1984) extends the rule on descent. He assumes the Naismith 's base speed of 5 km/h and makes the following further refinements for going downhill: [ 13 ] [ 15 ] [ 21 ]
Later he says that the fitness of the slowest member of a party should be taken into account and thus a more practical formula for a group is: [ 13 ] | https://en.wikipedia.org/wiki/Naismith's_rule |
In immunology , a naive B cell is a B cell that has not been exposed to an antigen . These are located in the tonsils , spleen , and primary lymphoid follicles in lymph nodes .
Once exposed to an antigen , the naive B cell either becomes a memory B cell or a plasma cell that secretes antibodies specific to the antigen that was originally bound. Plasma cells do not last long in the circulation; this is in contrast to memory cells that last for very long periods of time. Memory cells do not secrete antibodies until activated by their specific antigen. [ 1 ] [ 2 ]
Naive B cells play a key role in predicting humoral responses to COVID-19 mRNA vaccines in immunocompromised patients, specifically measuring naive B cell levels could help predict and improve vaccination outcomes. [ 3 ] | https://en.wikipedia.org/wiki/Naive_B_cell |
The Nakajima–Zwanzig equation (named after the physicists who developed it, Sadao Nakajima [ 1 ] and Robert Zwanzig [ 2 ] ) is an integral equation describing the time evolution of the "relevant" part of a quantum-mechanical system. It is formulated in the density matrix formalism and can be regarded as a generalization of the master equation .
The equation belongs to the Mori-Zwanzig formalism within the statistical mechanics of irreversible processes (named after Hazime Mori ). By means of a projection operator, the dynamics is split into a slow, collective part ( relevant part ) and a rapidly fluctuating irrelevant part. The goal is to develop dynamical equations for the collective part.
The Nakajima-Zwanzig (NZ) generalized master equation is a formally exact approach for simulating quantum dynamics in condensed phases. This framework is particularly designed to address the dynamics of a reduced system interact with a larger environment, often represented as a system coupled to a bath. Within the NZ framework, one can choose between time convolution (TC) and time convolution less (TCL) forms of the quantum master equations.
The TC approach involves memory effects, where the future state of the system depends on its entire history (Non-Markovian dynamics). The TCL approach formulates the dynamics where the system's rate of change at any moment depends only on its current state, simplifying calculations by neglecting memory effects (Markovian dynamics).
The total Hamiltonian of a system interacting with its environment (or bath) is typically expressed in system-bath form,
where H ^ S {\displaystyle {\hat {H}}_{S}} is the system Hamiltonian, H ^ B {\displaystyle {\hat {H}}_{B}} is the bath Hamiltonian, and H ^ S B {\displaystyle {\hat {H}}_{SB}} describes the coupling between them.
The starting point [ note 1 ] is the quantum mechanical version of the von Neumann equation , also known as the Liouville equation:
where the Liouville operator L {\displaystyle L} is defined as L A = i ℏ [ A , H ] {\displaystyle LA={\frac {i}{\hbar }}[A,H]} .
In the Nakajima-Zwanzig formulation, a key step involves defining a projection operator P {\displaystyle {\mathcal {P}}} that projects the total density operator ρ {\displaystyle \rho } onto the subspace of the system of interest. The complementary operator Q ≡ 1 − P {\displaystyle {\mathcal {Q}}\equiv 1-{\mathcal {P}}} projects onto the orthogonal subspace, effectively separating the system from the bath.
The Liouville – von Neumann equation can thus be represented as
The dynamics of the projected state P ρ {\displaystyle {\mathcal {P}}\rho } , under any idempotent projection operator (where P 2 = P {\displaystyle {\mathcal {P}}^{2}={\mathcal {P}}} ), is described by the NZ generalized master equation (GQME). This equation can be used to obtain a closed equation of motion for the reduced system dynamics, focusing solely on the dynamics within the subsystem of interest. d d t P ρ ^ ( t ) = − i ℏ P L P ρ ^ ( t ) − i ℏ 2 ∫ 0 t d τ P L e − i Q L τ / ℏ Q L P ρ ^ ( t − τ ) − i ℏ P L e − i Q L τ / ℏ Q ρ ^ ( 0 ) {\displaystyle {\frac {d}{dt}}{\mathcal {P}}{\hat {\rho }}(t)=-{\frac {i}{\hbar }}{\mathcal {P}}L{\mathcal {P}}{\hat {\rho }}(t)-{\frac {i}{\hbar ^{2}}}\int _{0}^{t}d\tau {\mathcal {P}}Le^{-i{\mathcal {Q}}L\tau /\hbar }{\mathcal {Q}}L{\mathcal {P}}{\hat {\rho }}(t-\tau )-{\frac {i}{\hbar }}{\mathcal {P}}Le^{-i{\mathcal {Q}}L\tau /\hbar }{\mathcal {Q}}{\hat {\rho }}(0)}
In practice, the specific form of the projection operator P {\displaystyle {\mathcal {P}}} can be chosen based on the problem at hand. One common choice involves defining P {\displaystyle {\mathcal {P}}} using a reference nuclear density operator ρ ^ n ref {\displaystyle {\hat {\rho }}_{n}^{\text{ref}}} such that Tr B { ρ ^ n ref } = 1 {\displaystyle {\text{Tr}}_{B}\{{\hat {\rho }}_{n}^{\text{ref}}\}=1} .
P ( ρ ) = ρ ^ n ref ⊗ Tr n { ρ } {\displaystyle {\mathcal {P}}(\rho )={\hat {\rho }}_{n}^{\text{ref}}\otimes {\text{Tr}}_{n}\{\rho \}}
This ensures that P {\displaystyle {\mathcal {P}}} remains idempotent. Using this projection, tracing over the nuclear Hilbert space leads to a generalized quantum master equation that describes the reduced electronic density operator which accounts for both Markovian dynamics generated by the Hamiltonian and non-Markovian dynamics due to coupling between electronic and nuclear degrees of freedom.
d d t σ ^ ( t ) = − i ℏ ( L ) n ref σ ^ ( t ) − ∫ 0 t d τ K ( τ ) σ ^ ( t − τ ) + I ^ ( t ) {\displaystyle {\frac {d}{dt}}{\hat {\sigma }}(t)=-{\frac {i}{\hbar }}(L)_{n}^{\text{ref}}{\hat {\sigma }}(t)-\int _{0}^{t}d\tau \,{\mathcal {K}}(\tau ){\hat {\sigma }}(t-\tau )+{\hat {I}}(t)}
This ⟨ L ⟩ n ref = Tr n { L ρ ^ n ref } {\displaystyle \langle L\rangle _{n}^{\text{ref}}={\text{Tr}}_{n}\{L{\hat {\rho }}_{n}^{\text{ref}}\}}
describes the dynamics driven by the Hamiltonian, ⟨ H ^ ⟩ n ref = Tr n { H ^ ρ n ref } {\displaystyle \langle {\hat {H}}\rangle _{n}^{\text{ref}}={\text{Tr}}_{n}\{{\hat {H}}\rho _{n}^{\text{ref}}\}} which are Hamiltonian and Markovian in nature, while the other two terms on the right-hand side represent the non-Hamiltonian and non-Markovian dynamics that arise from the interactions between the electronic and nuclear degrees of freedom.
The memory kernel K ( τ ) {\displaystyle {\mathcal {K}}(\tau )} captures the effects of the bath on the system over the time interval from (0, t), reflecting non-Markovian dynamics where the system's history influences its future evolution.
K ( τ ) = i ℏ 2 Tr n { L e − i Q L τ / ℏ Q L ρ ^ n ref } {\displaystyle {\mathcal {K}}(\tau )={\frac {i}{\hbar ^{2}}}\operatorname {Tr} _{n}\{Le^{-i{\mathcal {Q}}L\tau /\hbar }{\mathcal {Q}}L{\hat {\rho }}_{n}^{\text{ref}}\}}
The inhomogeneous term I ^ ( t ) {\displaystyle {\hat {I}}(t)} represents the influence of the initial state of the bath on the system at time t, which is crucial for accurately describing the system dynamics from an initial condition.
I ^ ( t ) = i ℏ Tr n { L e − i Q τ / ℏ Q ρ ^ n ( 0 ) } {\displaystyle {\hat {I}}(t)={\frac {i}{\hbar }}{\text{Tr}}_{n}\left\{Le^{-i{\mathcal {Q}}\tau /\hbar }{\mathcal {Q}}{\hat {\rho }}_{n}(0)\right\}}
The memory kernel is crucial for simulating the dynamics of the electronic degrees of freedom. However, calculating K ( τ ) {\displaystyle {\mathcal {K}}(\tau )} presents difficulties due to its time-dependent nature. Additionally, the time dependency of K ( τ ) {\displaystyle {\mathcal {K}}(\tau )} is complex because it is governed by the projection-dependent propagator, e − i Q L τ / ℏ {\displaystyle e^{-i{\mathcal {Q}}L\tau /\hbar }} . Therefore, the exact memory kernel is difficult to calculate except for several analytically solvable models proposed by Shi-Geva to remove the projection operator Q {\displaystyle {\mathcal {Q}}} . | https://en.wikipedia.org/wiki/Nakajima–Zwanzig_equation |
In cooperative game theory and social choice theory , the Nakamura number measures the degree of rationality
of preference aggregation rules (collective decision rules), such as voting rules.
It is an indicator of the extent to which an aggregation rule can yield well-defined choices.
In contrast,
The larger the Nakamura number a rule has, the greater the number of alternatives the rule can rationally deal with.
For example, since (except in the case of four individuals (voters)) the Nakamura number of majority rule is three,
the rule can deal with up to two alternatives rationally (without causing a paradox).
The number is named after Kenjiro Nakamura [ ja ] (1947–1979), a Japanese game theorist who proved the above fact
that the rationality of collective choice critically depends on the number of alternatives. [ 1 ]
To introduce a precise definition of the Nakamura number, we give an example of a "game" (underlying the rule in question)
to which a Nakamura number will be assigned.
Suppose the set of individuals consists of individuals 1, 2, 3, 4, and 5.
Behind majority rule is the following collection of ("decisive") coalitions (subsets of individuals) having at least three members:
A Nakamura number can be assigned to such collections, which we call simple games .
More precisely, a simple game is just an arbitrary collection of coalitions;
the coalitions belonging to the collection are said to be winning ; the others losing .
If all the (at least three, in the example above) members of a winning coalition prefer alternative x to alternative y,
then the society (of five individuals, in the example above) will adopt the same ranking ( social preference ).
The Nakamura number of a simple game is defined as the minimum number of winning coalitions with empty intersection .
(By intersecting this number of winning coalitions, one can sometimes obtain an empty set.
But by intersecting less than this number, one can never obtain an empty set.)
The Nakamura number of the simple game above is three, for example,
since the intersection of any two winning coalitions contains at least one individual
but the intersection of the following three winning coalitions is empty: { 1 , 2 , 3 } {\displaystyle \{1,2,3\}} , { 4 , 5 , 1 } {\displaystyle \{4,5,1\}} , { 2 , 3 , 4 } {\displaystyle \{2,3,4\}} .
Nakamura's theorem (1979 [ 2 ] ) gives the following necessary (also sufficient if the set of alternatives is finite) condition for a simple game to have a nonempty "core" (the set of socially "best" alternatives) for all profiles of individual preferences:
the number of alternatives is less than the Nakamura number of the simple game.
Here, the core of a simple game with respect to the profile of preferences is the set of all alternatives x {\displaystyle x} such that there is no alternative y {\displaystyle y} that every individual in a winning coalition prefers to x {\displaystyle x} ; that is, the set of maximal elements of the social preference.
For the majority game example above, the theorem implies that the core will be empty (no alternative will be deemed "best") for some profile,
if there are three or more alternatives.
Variants of Nakamura's theorem exist that provide a condition for the core to be nonempty
(i) for all profiles of acyclic preferences;
(ii) for all profiles of transitive preferences; and
(iii) for all profiles of linear orders .
There is a different kind of variant (Kumabe and Mihara, 2011 [ 3 ] ),
which dispenses with acyclicity , the weak requirement of rationality.
The variant gives a condition for the core to be nonempty for all profiles of preferences that have maximal elements .
For ranking alternatives, there is a very well known result called " Arrow's impossibility theorem " in social choice theory,
which points out the difficulty for a group of individuals in ranking three or more alternatives.
For choosing from a set of alternatives (instead of ranking them), Nakamura's theorem is more relevant. [ 5 ] An interesting question is how large the Nakamura number can be.
It has been shown that for a (finite or) algorithmically computable simple game that has no veto player
(an individual that belongs to every winning coalition)
to have a Nakamura number greater than three, the game has to be non-strong . [ 6 ] This means that there is a losing (i.e., not winning) coalition whose complement is also losing.
This in turn implies that nonemptyness of the core is assured for a set of three or more alternatives
only if the core may contain several alternatives that cannot be strictly ranked. [ 8 ]
Let N {\displaystyle N} be a (finite or infinite) nonempty set of individuals .
The subsets of N {\displaystyle N} are called coalitions .
A simple game (voting game) is a collection W {\displaystyle W} of coalitions.
(Equivalently, it is a coalitional game that assigns either 1 or 0 to each coalition.)
We assume that W {\displaystyle W} is nonempty and does not contain an empty set.
The coalitions belonging to W {\displaystyle W} are winning ; the others are losing .
A simple game W {\displaystyle W} is monotonic if S ∈ W {\displaystyle S\in W} and S ⊆ T {\displaystyle S\subseteq T} imply T ∈ W {\displaystyle T\in W} .
It is proper if S ∈ W {\displaystyle S\in W} implies N ∖ S ∉ W {\displaystyle N\setminus S\notin W} .
It is strong if S ∉ W {\displaystyle S\notin W} implies N ∖ S ∈ W {\displaystyle N\setminus S\in W} .
A veto player (vetoer) is an individual that belongs to all winning coalitions.
A simple game is nonweak if it has no veto player.
It is finite if there is a finite set (called a carrier ) T ⊆ N {\displaystyle T\subseteq N} such that for all coalitions S {\displaystyle S} ,
we have S ∈ W {\displaystyle S\in W} iff S ∩ T ∈ W {\displaystyle S\cap T\in W} .
Let X {\displaystyle X} be a (finite or infinite) set of alternatives , whose cardinal number (the number of elements) # X {\displaystyle \#X} is at least two.
A (strict) preference is an asymmetric relation ≻ {\displaystyle \succ } on X {\displaystyle X} :
if x ≻ y {\displaystyle x\succ y} (read " x {\displaystyle x} is preferred to y {\displaystyle y} "),
then y ⊁ x {\displaystyle y\not \succ x} .
We say that a preference ≻ {\displaystyle \succ } is acyclic (does not contain cycles ) if
for any finite number of alternatives x 1 , … , x m {\displaystyle x_{1},\ldots ,x_{m}} ,
whenever x 1 ≻ x 2 {\displaystyle x_{1}\succ x_{2}} , x 2 ≻ x 3 {\displaystyle x_{2}\succ x_{3}} ,…, x m − 1 ≻ x m {\displaystyle x_{m-1}\succ x_{m}} ,
we have x m ⊁ x 1 {\displaystyle x_{m}\not \succ x_{1}} . Note that acyclic relations are asymmetric, hence preferences.
A profile is a list p = ( ≻ i p ) i ∈ N {\displaystyle p=(\succ _{i}^{p})_{i\in N}} of individual preferences ≻ i p {\displaystyle \succ _{i}^{p}} .
Here x ≻ i p y {\displaystyle x\succ _{i}^{p}y} means that individual i {\displaystyle i} prefers alternative x {\displaystyle x} to y {\displaystyle y} at profile p {\displaystyle p} .
A simple game with ordinal preferences is a pair ( W , p ) {\displaystyle (W,p)} consisting
of a simple game W {\displaystyle W} and a profile p {\displaystyle p} .
Given ( W , p ) {\displaystyle (W,p)} , a dominance (social preference) relation ≻ W p {\displaystyle \succ _{W}^{p}} is defined
on X {\displaystyle X} by x ≻ W p y {\displaystyle x\succ _{W}^{p}y} if and only if there is a winning coalition S ∈ W {\displaystyle S\in W} satisfying x ≻ i p y {\displaystyle x\succ _{i}^{p}y} for all i ∈ S {\displaystyle i\in S} .
The core C ( W , p ) {\displaystyle C(W,p)} of ( W , p ) {\displaystyle (W,p)} is the set of alternatives undominated by ≻ W p {\displaystyle \succ _{W}^{p}} (the set of maximal elements of X {\displaystyle X} with respect to ≻ W p {\displaystyle \succ _{W}^{p}} ):
The Nakamura number ν ( W ) {\displaystyle \nu (W)} of a simple game W {\displaystyle W} is the size (cardinal number)
of the smallest collection of winning coalitions with empty intersection: [ 9 ]
if ∩ W = ∩ S ∈ W S = ∅ {\displaystyle \cap W=\cap _{S\in W}S=\emptyset } (no veto player); [ 2 ] otherwise, ν ( W ) = + ∞ {\displaystyle \nu (W)=+\infty } (greater than any cardinal number).
it is easy to prove that if W {\displaystyle W} is a simple game without a veto player, then 2 ≤ ν ( W ) ≤ # N {\displaystyle 2\leq \nu (W)\leq \#N} .
Examples for finitely many individuals ( N = { 1 , … , n } {\displaystyle N=\{1,\ldots ,n\}} ) (see Austen-Smith and Banks (1999), Lemma 3.2 [ 4 ] ).
Let W {\displaystyle W} be a simple game that is monotonic and proper.
Examples for at most countably many individuals ( N = { 1 , 2 , … } {\displaystyle N=\{1,2,\ldots \}} ).
Kumabe and Mihara (2008) comprehensively study the restrictions that various properties
(monotonicity, properness, strongness, nonweakness, and finiteness) for simple games
impose on their Nakamura number (the Table "Possible Nakamura Numbers" below summarizes the results).
In particular, they show that an algorithmically computable simple
game [ 10 ] without a veto player has a Nakamura number greater than 3 only if it is proper and nonstrong. [ 6 ]
Nakamura's theorem (Nakamura, 1979, Theorems 2.3 and 2.5 [ 2 ] ).
Let W {\displaystyle W} be a simple game. Then the core C ( W , p ) {\displaystyle C(W,p)} is nonempty for all profiles p {\displaystyle p} of acyclic preferences if and only if X {\displaystyle X} is finite and # X < ν ( W ) {\displaystyle \#X<\nu (W)} .
Remarks
In this section, we discard the usual assumption of acyclic preferences.
Instead, we restrict preferences to those having a maximal element on a given agenda ( opportunity set that a group of individuals are confronted with),
a subset of some underlying set of alternatives.
(This weak restriction on preferences might be of some interest from the viewpoint of behavioral economics .)
Accordingly, it is appropriate to think of X {\displaystyle X} as an agenda here.
An alternative x ∈ X {\displaystyle x\in X} is a maximal element with respect to ≻ i p {\displaystyle \succ _{i}^{p}} (i.e., ≻ i p {\displaystyle \succ _{i}^{p}} has a maximal element x {\displaystyle x} ) if there is no y ∈ X {\displaystyle y\in X} such that y ≻ i p x {\displaystyle y\succ _{i}^{p}x} . If a preference is acyclic over the underlying set of alternatives, then it has a maximal element on every finite subset X {\displaystyle X} .
We introduce a strengthening of the core before stating the variant of Nakamura's theorem.
An alternative x {\displaystyle x} can be in the core C ( W , p ) {\displaystyle C(W,p)} even if there is a winning coalition of individuals i {\displaystyle i} that are "dissatisfied" with x {\displaystyle x} (i.e., each i {\displaystyle i} prefers some y i {\displaystyle y_{i}} to x {\displaystyle x} ).
The following solution excludes such an x {\displaystyle x} : [ 3 ]
It is easy to prove that C + ( W , p ) {\displaystyle C^{+}(W,p)} depends only on the set of maximal elements of each individual and is included in the union of such sets.
Moreover, for each profile p {\displaystyle p} , we have C + ( W , p ) ⊆ C ( W , p ) {\displaystyle C^{+}(W,p)\subseteq C(W,p)} .
A variant of Nakamura's theorem (Kumabe and Mihara, 2011, Theorem 2 [ 3 ] ).
Let W {\displaystyle W} be a simple game. Then the following three statements are equivalent:
Remarks | https://en.wikipedia.org/wiki/Nakamura_number |
The Nakanishi Prize , named after Japanese chemist Koji Nakanishi , is an award in chemistry given alternately by the Chemical Society of Japan and the American Chemical Society .
"To recognize and stimulate significant work that extends chemical and spectroscopic methods to the study of important biological phenomena." [ 1 ]
In 1995, friends and colleagues of Nakanishi established the Nakanishi Prize. It was decided that the Chemical Society of Japan and the American Chemical Society would alternate years awarding the prize. There are two separate endowments for the prize for each society, but the prize is the same for both awards: a medallion in presentation box, $5,000 prize money, and $2,500 travel reimbursements.
Source: American Chemical Society
Osaka University
Okinawa Science and Technology Promotion Center | https://en.wikipedia.org/wiki/Nakanishi_Prize |
Nakshatra ( Sanskrit : नक्षत्रम् , romanized : Nakṣatram ) is the term for Lunar mansion in Hindu astrology and Buddhist astrology. A nakshatra is one of 27 (sometimes also 28) sectors along the ecliptic. Their names are related to a prominent star or asterisms in or near the respective sectors. In essence (in Western astronomical terms), a nakshatra simply is a constellation . Every nakshatra is divided into four padas ( lit. "steps").
The starting point for the nakshatras according to the Vedas is "Krittika" (it has been argued because the Pleiades may have started the year at the time the Vedas were compiled, presumably at the vernal equinox), but, in more recent compilations, the start of the nakshatras list is the point on the ecliptic directly opposite to the star Spica , called Chitrā in Sanskrit . This translates to Ashwinī, a part of the modern constellation of Aries. These compilations, therefore may have been compiled during the centuries when the sun was passing through Aries at the time of the vernal equinox. This version may have been called Meshādi or the " start of Aries ". [ 1 ] [ full citation needed ]
The first astronomical text that lists them is the Vedanga Jyotisha . [ 2 ] [ better source needed ]
In classical Hindu scriptures ( Mahabharata , Harivamsa ), the creation of the asterisms is attributed to Daksha . [ 3 ] The Nakshatras are personified as daughters of Daksha and as wives of Chandra , the god of the Moon. When Chandra neglected his 26 other wives in favour of Rohini , his father-in-law cursed him with leprosy and proclaimed that the Moon would wax and wane each month. [ 4 ] The Nakshatras are also alternatively described as the daughters of Kashyapa .
In the Atharvaveda (Shaunakiya recension, hymn 19.7) a list of 27 stars or asterisms is given, many of them corresponding to the later nakshatras: [ 5 ] [ a ]
This 27-day cycle has been taken to mean a particular group of stars. This has to do with the periodicity with which the Moon travels past the specific star fields called nakshatras. Hence, the stars are more like numbers on a clock, through which the hands of time (the moon) pass. This concept is described by J. Mercay (2012) in connection with Surya Siddhanta . [ 6 ]
In Hindu astronomy, there was an older tradition of 28 Nakshatras which were used as celestial markers in the heavens. When these were mapped into equal divisions of the ecliptic, a division of 27 portions was adopted since that resulted in a clearer definition of each portion (i.e. segment) subtending 13° 20′ (as opposed to 12° 51 + 3 ⁄ 7 ′ in the case of 28 segments). In the process, the Nakshatra Abhijit was left out without a portion. [ 7 ] : 179 However, the Abhijit nakshatra becomes important while deciding on the timing of an auspicious event. The Surya Siddhantha concisely specifies the coordinates of the twenty-seven Nakshatras. [ 7 ] : 211
It is noted above that with the older tradition of 28 Nakshatras each equal segment would subtend 12.85 degrees or 12° 51′. But the 28 Nakshatra were chosen at a time when the Vedic month was recognised as having exactly 30 days. In India and China the original 28 lunar mansions were not equal. Weixing Nui provides a list of the extent of the original 28 Nakshatras expressed in Muhurtas (with one Muhurta = 48 minutes of arc). Hindu texts note there were 16 Nakshatras of 30 Muhurtas, 6 of 45 Muhurtas, 5 of 15 Muhurtas and one of 6 Muhurtas.
The 28 mansions of the 360° lunar zodiac total 831 Muhurtas or 27.7 days. This is sometimes described as an inaccurate estimate of our modern sidereal period of 27.3 days, but using the ancient Indian calendar with Vedic months of 30 days and a daily movement of the Moon of 13 degrees, this early designation of a sidereal month of 831 Muhurtas or 27.7 days is very precise. [ b ] [ 8 ] [ full citation needed ] Later some Indian savants dropped the Nakshatra named Abhijit to reduce the number of divisions to 27, but the Chinese retained all of their original 28 lunar mansions. These were grouped into four equal quarters which would have been fundamentally disrupted if it had been decided to reduce the number of divisions to 27.
Irrespective of the reason why ancient early Indian astronomers followed a Vedic calendar of exactly 12 months of 30 days it was this calendar and not a modern calendar of 365 days that they used for the astronomical calculations for the number of days taken for the Moon to complete one sidereal cycle of 360°. This is why initially they named 28 Nakshatras on their lunar zodiac. [ 9 ]
The following list of nakshatras gives the corresponding regions of sky, per Basham (1954). [ 10 ]
Each of the 27 Nakshatras cover 13° 20’ of the ecliptic each. Each Nakshatra is also divided into quarters or padas of 3° 20’, and the below table lists the appropriate starting sound to name the child. The 27 nakshatras, each with 4 padas, give 108, which is the number of beads in a japa mala, representing all the elements (ansh) of Vishnu:
Nakshatra is one of the five elements of a Pañcāṅga . The other four elements:
1 citrā́ṇi sākáṃ diví rocanā́ni sarīsr̥pā́ṇi bhúvane javā́ni turmíśaṃ sumatím ichámāno áhāni gīrbhíḥ saparyāmi nā́kam 2 suhávam agne kŕ̥ttikā róhiṇī cā́stu bhadráṃ mr̥gáśiraḥ śám ārdrā́ púnarvasū sūnŕ̥tā cā́ru púṣyo bhānúr āśleṣā́ áyanaṃ maghā́ me 3 púṇyaṃ pū́rvā phálgunyau cā́tra hástaś citrā́ śivā́ svātí sukhó me astu rā́dhe viśā́khe suhávānurādhā́ jyéṣṭhā sunákṣatram áriṣṭa mū́lam 4 ánnaṃ pū́rvā rāsatāṃ me aṣādhā́ ū́rjaṃ devy úttarā ā́ vahantu abhijín me rāsatāṃ púṇyam evá śrávaṇaḥ śráviṣṭhāḥ kurvatāṃ supuṣṭím 5 ā́ me mahác chatábhiṣag várīya ā́ me dvayā́ próṣṭhapadā suśárma ā́ revátī cāśvayújau bhágaṃ ma ā́ me rayíṃ bháraṇya ā́ vahantu [ 5 ] | https://en.wikipedia.org/wiki/Nakshatra |
See text
Naldaviricetes is a class of viruses , which infect arthropods . [ 1 ] Members of Naldaviricetes are characterized by large enveloped rod-shaped virions, circular double-stranded DNA genomes, and replication in the nucleus of the host cell. All of them (including the unassigned Polydnaviridae family) share a set of unique genes not found in other viruses, which include the presence of multiple interspersed direct repeats, various subunits of DNA polymerase and RNA polymerase , four late expression factor genes, and infectivity factor genes suggesting a common host entry mechanism. [ 2 ]
These viruses encompass several genes that are distantly related to core genes of the Nucleocytoviricota and thus could be highly derived members of the DJR-MCP viruses (kingdom Bamfordvirae of the realm Varidnaviria ), despite the absence of the DJR-MCP and formation of odd-shaped virions. Preliminary phylogenetic analysis of several essential genes that are shared by all these arthoropod viruses and the Nucleocytoviricota , such as PolB, RNAP subunits, helicase-primase and thiol oxidoreductase, has suggested that this group of viruses might be a highly derived offshoot of the Nucleocytoviricota . [ 3 ] [ 4 ]
Naldaviricetes contains one order and a family unassigned to an order. This taxonomy is shown hereafter: [ 1 ]
The unassigned family Polydnaviridae is a potential member of the group because they share the characteristic genes of Naldaviricetes and appear to have evolved from nudiviruses of the order Lefavirales . [ 3 ] [ 4 ]
This virus -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Naldaviricetes |
In quantum field theory , the Nambu–Jona-Lasinio model (or more precisely: the Nambu and Jona-Lasinio model ) is a complicated effective theory of nucleons and mesons constructed from interacting Dirac fermions with chiral symmetry , paralleling the construction of Cooper pairs from electrons in the BCS theory of superconductivity . The "complicatedness" of the theory has become more natural as it is now seen as a low-energy approximation of the still more basic theory of quantum chromodynamics , which does not work perturbatively at low energies.
The model is much inspired by the different field of solid state theory , particularly from the BCS breakthrough of 1957. The model was introduced in a joint article of Yoichiro Nambu (who also contributed essentially to the theory of superconductivity, i.e., by the "Nambu formalism") and Giovanni Jona-Lasinio , published in 1961. [ 1 ] A subsequent paper included chiral symmetry breaking , isospin and strangeness . [ 2 ] Around that time, the same model was independently considered by Soviet physicists Valentin Vaks and Anatoly Larkin . [ 3 ] [ 4 ]
The model is quite technical, although based essentially on symmetry principles. It is an example of the importance of four-fermion interactions and is defined in a spacetime with an even number of dimensions. It is still important and is used primarily as an effective although not rigorous low energy substitute for quantum chromodynamics.
The dynamical creation of a condensate from fermion interactions inspired many theories of the breaking of electroweak symmetry , such as technicolor and the top-quark condensate .
Starting with the one- flavor case first, the Lagrangian density is
or, equivalently, decomposed into left and right chiral parts,
The terms proportional to λ {\displaystyle \ \lambda \ } are an attractive four-fermion interaction, which parallels the BCS theory phonon exchange interaction.
The global symmetry of the model is U(1) Q × U(1) χ where Q is the ordinary charge of the Dirac fermion and χ is the chiral charge. The parameter λ {\displaystyle \ \lambda \ } is equivalent to a reciprocal squared mass, λ = 1 M 2 , {\displaystyle \ \lambda ={\tfrac {1}{\ M^{2}}}\ ,} which represents short-distance physics or
the strong interaction scale, producing an attractive four-fermion interaction.
There is no bare fermion mass term because of the chiral symmetry. However, there will be a chiral condensate (but no confinement ) leading to an effective mass term and a spontaneous symmetry breaking of the chiral symmetry, but not the charge symmetry.
With N flavors and the flavor indices, represented by the Latin letters a and b , the Lagrangian density becomes
hence
Chiral symmetry forbids a bare mass term, but there may be chiral condensates. The global symmetry here is SU( N ) L × SU( N ) R × U(1) Q × U(1) χ where SU( N ) L × SU( N ) R acting upon the left-handed flavors and right-handed flavors respectively is the chiral symmetry (in other words, there is no natural correspondence between the left-handed and the right-handed flavors), U(1) Q is the Dirac charge, which is sometimes called the baryon number and U(1) χ is the axial charge . If a chiral condensate forms, then the chiral symmetry is spontaneously broken into a diagonal subgroup SU( N ) since the condensate leads to a pairing of the left-handed and the right-handed flavors. The axial charge is also spontaneously broken.
The broken symmetries lead to (nearly) massless pseudoscalar bosons, e.g. pions . See Goldstone boson .
As mentioned, this model is sometimes used as a phenomenological model of quantum chromodynamics in the chiral limit . However, while it is able to model chiral symmetry breaking and chiral condensates, it does not model confinement. Also, the axial symmetry is broken spontaneously in this model, leading to a massless Goldstone boson unlike QCD, where it is broken anomalously.
Since the Nambu–Jona-Lasinio model is nonrenormalizable in four spacetime dimensions, this theory can only be an effective field theory which needs to be UV completed . | https://en.wikipedia.org/wiki/Nambu–Jona-Lasinio_model |
In computer programming , a name collision is the nomenclature problem that occurs when the same variable name is used for different things in two separate areas that are joined, merged, or otherwise go from occupying separate namespaces to sharing one. As with the collision of other identifiers , it must be resolved in some way [ a ] for the new software (such as a mashup ) to work right. [ 1 ] Problems of name collision, and methods to avoid them, are a common issue in an introductory level analysis of computer languages , such as for C++ . [ 1 ]
The term "name collision" has been used in computer science for more than three decades, when referring to names in various classification systems. [ 2 ]
There are several techniques for avoiding name collisions, including the use of:
This programming-language -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Name_collision |
A name reaction (or named reaction ) is a chemical reaction named after its discoverer(s) or developer(s). Among the tens of thousands of organic reactions that are known, hundreds of such reactions are typically identified by the eponym . [ 1 ] Well-known examples include the Grignard reaction , the Sabatier reaction , the Wittig reaction , the Claisen condensation , the Friedel–Crafts acylation , and the Diels–Alder reaction . Books have been published devoted exclusively to name reactions; [ 2 ] [ 3 ] [ 4 ] the Merck Index , a chemical encyclopedia, also includes an appendix on name reactions.
As organic chemistry developed during the 20th century, chemists started associating synthetically useful reactions with the names of their discoverers or developers. In many cases, the name is merely a mnemonic. [ 2 ] Some reactions such as the Pummerer rearrangement , [ 3 ] the Pinnick oxidation and the Birch reduction [ 3 ] are named for people other than their discoverers, but this situation is not common.
Although systematic approaches for naming reactions based on the reaction mechanism or the overall transformation exist, such as the IUPAC nomenclature for organic chemical transformations , these technically-descriptive names are often unwieldy or not specific enough, so people names are often more practical for efficient communication. [ 5 ] | https://en.wikipedia.org/wiki/Name_reaction |
In computer systems, name resolution refers to the retrieval of the underlying numeric values corresponding to computer hostnames, account user names, group names, and other named entities.
Computer operating systems commonly employ multiple key/value lists that associate easily remembered names with integer numbers used to identify users, groups, other computers, hardware devices, and other entities. In that context, name resolution refers to the retrieval of numeric values given the associated names, while reverse name resolution refers to the opposite process of finding name(s) associated with specified numeric values:
The GNU C Library provides various operating system facilities that shell commands and other applications can call to resolve such names to the corresponding addresses or IDs, and vice versa. Some Linux distributions use an nsswitch.conf file to specify the order in which multiple resolution services are used to effect such lookups.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Name_resolution_(computer_systems) |
There are currently 118 known chemical elements with a wide range of physical and chemical properties. Amongst this diversity, scientists have found it useful to apply names for various sets of elements that have similar properties, to varying degrees. Many of these sets are formally recognized by the standards body IUPAC . [ 1 ]
The following collective names are recommended or noted by IUPAC:
Another common classification is by degree of metallic or nonmetallic behaviour and characteristics. Elements in the vicinity of where the metals and nonmetals meet are sometime classified as metalloids or an equivalent term. These two to three classes are commonly marked by differing background colors in the periodic table.
Many other names for sets of elements are in common use; others have been used throughout history. These sets usually do not aim to cover the whole periodic table (as for example period does), and often overlap or have boundaries that differ between authors. Some examples:
In alphabetic order: | https://en.wikipedia.org/wiki/Names_for_sets_of_chemical_elements |
Depending on context (e.g. language, culture, region), some large numbers have names that allow for describing large quantities in a textual form; not mathematical . For very large values, the text is generally shorter than a decimal numeric representation although longer than scientific notation .
Two naming scales for large numbers have been used in English and other European languages since the early modern era: the long and short scales . Most English variants use the short scale today, but the long scale remains dominant in many non-English-speaking areas, including continental Europe and Spanish -speaking countries in Latin America . These naming procedures are based on taking the number n occurring in 10 3 n +3 (short scale) or 10 6 n (long scale) and concatenating Latin roots for its units, tens, and hundreds place, together with the suffix -illion .
Names of numbers above a trillion are rarely used in practice; such large numbers have practical usage primarily in the scientific domain, where powers of ten are expressed as 10 with a numeric superscript. However, these somewhat rare names are considered acceptable for approximate statements. For example, the statement "There are approximately 7.1 octillion atoms in an adult human body" is understood to be in short scale of the table below (and is only accurate if referring to short scale rather than long scale).
The Indian numbering system uses the named numbers common between the long and short scales up to ten thousand. For larger values, it includes named numbers at each multiple of 100; including lakh (10 5 ) and crore (10 7 ). [ 1 ]
English also has words, such as zillion , that are used informally to mean large but unspecified amounts .
Usage:
Apart from million , the words in this list ending with - illion are all derived by adding prefixes ( bi -, tri -, etc., derived from Latin) to the stem - illion . [ 11 ] Centillion [ 12 ] appears to be the highest name ending in -"illion" that is included in these dictionaries. Trigintillion , often cited as a word in discussions of names of large numbers, is not included in any of them, nor are any of the names that can easily be created by extending the naming pattern ( unvigintillion , duovigintillion , duoquinquagintillion , etc.).
All of the dictionaries included googol and googolplex , generally crediting it to the Kasner and Newman book and to Kasner's nephew (see below). None include any higher names in the googol family (googolduplex, etc.). The Oxford English Dictionary comments that googol and googolplex are "not in formal mathematical use".
Some names of large numbers, such as million , billion , and trillion , have real referents in human experience, and are encountered in many contexts, particularly in finance and economics. At times, the names of large numbers have been forced into common usage as a result of hyperinflation . The highest numerical value banknote ever printed was a note for 1 sextillion pengő (10 21 or 1 milliard bilpengő as printed) printed in Hungary in 1946. In 2009, Zimbabwe printed a 100 trillion (10 14 ) Zimbabwean dollar note, which at the time of printing was worth about US$30. [ 13 ] In global economics, the name of a significantly larger number was used in 2024, when the Russian news outlet RBK stated that the sum of legal claims against Google in Russia totalled 2 undecillion (2 × 10 36 ) rubles , or US $20 decillion (US $2 × 10 34 ); a value worth more than all financial assets in the world combined. [ 14 ] A Kremlin spokesperson, Dmitry Peskov , stated that this value was symbolic. [ 15 ]
Names of larger numbers, however, have a tenuous, artificial existence, rarely found outside definitions, lists, and discussions of how large numbers are named. Even well-established names like sextillion are rarely used, since in the context of science, including astronomy, where such large numbers often occur, they are nearly always written using scientific notation . In this notation, powers of ten are expressed as 10 with a numeric superscript, e.g. "The X-ray emission of the radio galaxy is 1.3 × 10 45 joules ." When a number such as 10 45 needs to be referred to in words, it is simply read out as "ten to the forty-fifth" or "ten to the forty-five". This is easier to say and less ambiguous than "quattuordecillion", which means something different in the long scale and the short scale.
When a number represents a quantity rather than a count, SI prefixes can be used—thus " femtosecond ", not "one quadrillionth of a second"—although often powers of ten are used instead of some of the very high and very low prefixes. In some cases, specialized units are used, such as the astronomer's parsec and light year or the particle physicist's barn .
Nevertheless, large numbers have an intellectual fascination and are of mathematical interest, and giving them names is one way people try to conceptualize and understand them.
One of the earliest examples of this is The Sand Reckoner , in which Archimedes gave a system for naming large numbers. To do this, he called the numbers up to a myriad myriad (10 8 ) "first numbers" and called 10 8 itself the "unit of the second numbers". Multiples of this unit then became the second numbers, up to this unit taken a myriad myriad times, 10 8 ·10 8 =10 16 . This became the "unit of the third numbers", whose multiples were the third numbers, and so on. Archimedes continued naming numbers in this way up to a myriad myriad times the unit of the 10 8 -th numbers, i.e. ( 10 8 ) ( 10 8 ) = 10 8 ⋅ 10 8 , {\displaystyle (10^{8})^{(10^{8})}=10^{8\cdot 10^{8}},} and embedded this construction within another copy of itself to produce names for numbers up to ( ( 10 8 ) ( 10 8 ) ) ( 10 8 ) = 10 8 ⋅ 10 16 . {\displaystyle ((10^{8})^{(10^{8})})^{(10^{8})}=10^{8\cdot 10^{16}}.} Archimedes then estimated the number of grains of sand that would be required to fill the known universe, and found that it was no more than "one thousand myriad of the eighth numbers" (10 63 ).
Since then, many others have engaged in the pursuit of conceptualizing and naming numbers that have no existence outside the imagination. One motivation for such a pursuit is that attributed to the inventor of the word googol , who was certain that any finite number "had to have a name". Another possible motivation is competition between students in computer programming courses, where a common exercise is that of writing a program to output numbers in the form of English words. [ citation needed ]
Most names proposed for large numbers belong to systematic schemes which are extensible. Thus, many names for large numbers are simply the result of following a naming system to its logical conclusion—or extending it further. [ citation needed ]
The words bymillion and trimillion were first recorded in 1475 in a manuscript of Jehan Adam . Subsequently, Nicolas Chuquet wrote a book Triparty en la science des nombres which was not published during Chuquet's lifetime. However, most of it was copied by Estienne de La Roche for a portion of his 1520 book, L'arismetique . Chuquet's book contains a passage in which he shows a large number marked off into groups of six digits, with the comment:
Ou qui veult le premier point peult signiffier million Le second point byllion Le tiers point tryllion Le quart quadrillion Le cinq e quyllion Le six e sixlion Le sept. e septyllion Le huyt e ottyllion Le neuf e nonyllion et ainsi des ault' s se plus oultre on vouloit preceder
(Or if you prefer the first mark can signify million, the second mark byllion, the third mark tryllion, the fourth quadrillion, the fifth quyillion, the sixth sixlion, the seventh septyllion, the eighth ottyllion, the ninth nonyllion and so on with others as far as you wish to go).
Adam and Chuquet used the long scale of powers of a million; that is, Adam's bymillion (Chuquet's byllion ) denoted 10 12 , and Adam's trimillion (Chuquet's tryllion ) denoted 10 18 .
The names googol and googolplex were invented by Edward Kasner 's nephew Milton Sirotta and introduced in Kasner and Newman's 1940 book Mathematics and the Imagination [ 16 ] in the following passage:
The name "googol" was invented by a child (Dr. Kasner's nine-year-old nephew) who was asked to think up a name for a very big number, namely 1 with one hundred zeroes after it. He was very certain that this number was not infinite, and therefore equally certain that it had to have a name. At the same time that he suggested "googol" he gave a name for a still larger number: "googolplex". A googolplex is much larger than a googol, but is still finite, as the inventor of the name was quick to point out. It was first suggested that a googolplex should be 1, followed by writing zeros until you got tired. This is a description of what would happen if one tried to write a googolplex, but different people get tired at different times and it would never do to have Carnera a better mathematician than Dr. Einstein , simply because he had more endurance. The googolplex is, then, a specific finite number, equal to 1 with a googol zeros after it.
John Horton Conway and Richard K. Guy [ 17 ] have suggested that N-plex be used as a name for 10 N . This gives rise to the name googolplexplex for 10 googolplex = 10 10 10 100 . Conway and Guy [ 17 ] have proposed that N-minex be used as a name for 10 −N , giving rise to the name googolminex for the reciprocal of a googolplex, which is written as 10 -(10 100 ) . None of these names are in wide use.
The names googol and googolplex inspired the name of the Internet company Google and its corporate headquarters , the Googleplex , respectively. [ 18 ]
This section illustrates several systems for naming large numbers, and shows how they can be extended past vigintillion .
Traditional British usage assigned new names for each power of one million (the long scale ): 1,000,000 = 1 million ; 1,000,000 2 = 1 billion ; 1,000,000 3 = 1 trillion ; and so on. It was adapted from French usage, and is similar to the system that was documented or invented by Chuquet .
Traditional American usage (which was also adapted from French usage but at a later date), Canadian, and modern British usage assign new names for each power of one thousand (the short scale ). Thus, a billion is 1000 × 1000 2 = 10 9 ; a trillion is 1000 × 1000 3 = 10 12 ; and so forth. Due to its dominance in the financial world (and by the US dollar ), this was adopted for official United Nations documents.
Traditional French usage has varied; in 1948, France, which had originally popularized the short scale worldwide, reverted to the long scale.
The term milliard is unambiguous and always means 10 9 . It is seldom seen in American usage and rarely in British usage, but frequently in continental European usage. The term is sometimes attributed to French mathematician Jacques Peletier du Mans c. 1550 (for this reason, the long scale is also known as the Chuquet-Peletier system), but the Oxford English Dictionary states that the term derives from post-Classical Latin term milliartum , which became milliare and then milliart and finally our modern term.
Concerning names ending in -illiard for numbers 10 6 n +3 , milliard is certainly in widespread use in languages other than English, but the degree of actual use of the larger terms is questionable. The terms "milliardo" in Italian, "Milliarde" in German, "miljard" in Dutch, "milyar" in Turkish, and "миллиард," milliard (transliterated) in Russian, are standard usage when discussing financial topics.
The naming procedure for large numbers is based on taking the number n occurring in 10 3 n +3 (short scale) or 10 6 n (long scale) and concatenating Latin roots for its units, tens, and hundreds place, together with the suffix -illion . In this way, numbers up to 10 3·999+3 = 10 3000 (short scale) or 10 6·999 = 10 5994 (long scale) may be named. The choice of roots and the concatenation procedure is that of the standard dictionary numbers if n is 9 or smaller. For larger n (between 10 and 999), prefixes can be constructed based on a system described by Conway and Guy. [ 17 ] Today, sexdecillion and novemdecillion are standard dictionary numbers and, using the same reasoning as Conway and Guy did for the numbers up to nonillion, could probably be used to form acceptable prefixes. The Conway–Guy system for forming prefixes: [ 17 ] : 15
Since the system of using Latin prefixes will become ambiguous for numbers with exponents of a size which the Romans rarely counted to, like 10 6,000,258 , Conway and Guy co-devised with Allan Wechsler the following set of consistent conventions that permit, in principle, the extension of this system indefinitely to provide English short-scale names for any integer whatsoever. [ 17 ] The name of a number 10 3 n +3 , where n is greater than or equal to 1000, is formed by concatenating the names of the numbers of the form 10 3 m +3 , where m represents each group of comma-separated digits of n , with each but the last "-illion" trimmed to "-illi-", or, in the case of m = 0, either "-nilli-" or "-nillion". [ 17 ] For example, 10 3,000,012 , the 1,000,003rd "-illion" number, equals one "millinillitrillion"; 10 33,002,010,111 , the 11,000,670,036th "-illion" number, equals one "undecillinilliseptuagintasescentillisestrigintillion"; and 10 29,629,629,633 , the 9,876,543,210th "-illion" number, equals one "nonilliseseptuagintaoctingentillitresquadragintaquingentillideciducentillion". [ 17 ]
The following table shows number names generated by the system described by Conway and Guy for the short and long scales. [ 19 ]
The International System of Quantities (ISQ) defines a series of prefixes denoting integer powers of 1024 between 1024 1 and 1024 8 . [ 21 ] | https://en.wikipedia.org/wiki/Names_of_large_numbers |
This is a list of the names of small decimal numbers in English .
The following table lists the names of small numbers used in the long and short scales , along with the power of 10 , engineering notation , and International System of Units (SI) symbols and prefixes. [ 1 ] [ page needed ] [ 2 ] [ page needed ] [ 3 ] [ page needed ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] | https://en.wikipedia.org/wiki/Names_of_small_numbers |
A Wagner–Meerwein rearrangement is a class of carbocation 1,2-rearrangement reactions in which a hydrogen , alkyl or aryl group migrates from one carbon to a neighboring carbon. [ 1 ] [ 2 ] They can be described as cationic [1,2]- sigmatropic rearrangements, proceeding suprafacially and with stereochemical retention. As such, a Wagner–Meerwein shift is a thermally allowed pericyclic process with the Woodward-Hoffmann symbol [ ω 0 s + σ 2 s ]. They are usually facile, and in many cases, they can take place at temperatures as low as –120 °C. The reaction is named after the Russian chemist Yegor Yegorovich Vagner ; he had German origin and published in German journals as Georg Wagner; and Hans Meerwein .
Several reviews have been published. [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The rearrangement was first discovered in bicyclic terpenes for example the conversion of isoborneol to camphene : [ 8 ]
The story of the rearrangement reveals that many scientists were puzzled with this and related reactions and its close relationship to the discovery of carbocations as intermediates. [ 9 ]
In a simple demonstration reaction of 1,4-dimethoxybenzene with either 2-methyl-2-butanol or 3-methyl-2-butanol in sulfuric acid and acetic acid yields the same disubstituted product, [ 10 ] the latter via a hydride shift of the cationic intermediate:
Currently, there are works relating to the use of skeletal rearrangement in the synthesis of bridged azaheterocycles . These data are summarized in [ 11 ]
Plausible mechanisms of the Wagner–Meerwein rearrangement of diepoxyisoindoles :
The related Nametkin rearrangement , named after Sergey Namyotkin , involves the rearrangement of methyl groups in certain terpenes. In some cases the reaction type is also called a retropinacol rearrangement (see pinacol rearrangement ). | https://en.wikipedia.org/wiki/Nametkin_rearrangement |
The Namhŭng Youth Chemical Complex is a large industrial complex in Namhŭng-dong, Anju-si , South P'yŏngan province, North Korea , and is one of the most important chemical factories in the country, being a major producer of chemical products such as fertilisers, herbicides, insecticides, various industrial chemicals. various plastics such as polyethylene sheeting, and various synthetic textiles. [ 1 ] It is also believed to produce chemical weapons such as cyanogen chloride and mustard gas . [ 2 ]
The complex was originally built in 1976 with French , Japanese and West German equipment, initially producing ammonia by naphtha gasification, acrylic and polycarbonate fibres, and urea fertiliser, [ 1 ] using naphtha brought in from the Sŭngri and Ponghwa chemical factories . In 2000, new equipment was installed to produce sodium carbonate , and renovations of the complex began in 2006. Also in 2006, the construction of a new anthracite gasification plant began; [ 2 ] this was opened in 2010, and its output is being used to produce fertiliser, and by 2011 a second gasification plant was opened. [ 1 ]
The facility is served by the Korean State Railway via Namhŭng station on the Namhŭng Line . It also has its own fleet of shunting locomotives, along with facilities for the maintenance of rail equipment. [ 1 ] | https://en.wikipedia.org/wiki/Namhung_Youth_Chemical_Complex |
In functional analysis , Namioka's theorem is a result concerning the relationship between separate continuity and joint continuity of functions defined on product spaces . Named after mathematician Isaac Namioka , who proved it in his 1974 paper Separate Continuity and Joint Continuity published in the Pacific Journal of Mathematics , the theorem establishes conditions under which a separately continuous function must be jointly continuous on a topologically large subset of its domain . [ 1 ]
Namioka's theorem . Let X {\displaystyle X} be a Čech-complete topological space (such as a complete metric space ), Y {\displaystyle Y} be a compact Hausdorff space , and Z {\displaystyle Z} be a metric space . If f : X × Y → Z {\displaystyle f:X\times Y\rightarrow Z} is separately continuous , meaning that
then there exists a dense G δ {\displaystyle G_{\delta }} -subset G {\displaystyle G} of X {\displaystyle X} such that f {\displaystyle f} is jointly continuous at each point of G × Y {\displaystyle G\times Y} . [ 1 ] [ 2 ]
Namioka's theorem can be equivalently stated in terms of the set C ( f ) {\displaystyle C(f)} of points where f {\displaystyle f} is continuous, stating that the projection of C ( f ) {\displaystyle C(f)} onto X {\displaystyle X} contains a dense G δ {\displaystyle G_{\delta }} subset of X {\displaystyle X} . [ 1 ] [ 2 ]
French mathematician René Baire was among the first to systematically study the relationship between separate and joint continuity in 1899, for real-valued functions of real variables. [ 3 ] Austrian mathematician Hans Hahn later extended these investigations in 1932, proving similar results for functions defined on complete metric spaces. [ 4 ] Namioka generalized these results to non-metrizable spaces , particularly to Čech-complete spaces, which include all complete metric spaces as a special case . There exists a proof using tools from general topology such as the Arkhangel'skii–Frolík covering theorem and the Kuratowski and Ryll-Nardzewski measurable selection theorem . [ 2 ] | https://en.wikipedia.org/wiki/Namioka's_theorem |
Nanaerobes are organisms that cannot grow in the presence of micromolar concentrations of oxygen, but can grow with and benefit from the presence of nanomolar concentrations of oxygen (e.g. Bacteroides fragilis ). [ 1 ] Like other anaerobes , these organisms do not require oxygen for growth. This growth benefit requires the expression of an oxygen respiratory chain that is typically associated with microaerophilic respiration. Recent studies suggest that respiration in low concentrations of oxygen is an ancient process which predates the emergence of oxygenic photosynthesis . | https://en.wikipedia.org/wiki/Nanaerobe |
The Nancy Grace Roman Space Telescope (shortened as the Roman Space Telescope , Roman , or RST ) is a NASA infrared space telescope in development and scheduled to launch to a Sun–Earth L 2 orbit by May 2027. [ 5 ] It is named after former NASA Chief of Astronomy Nancy Grace Roman .
The Roman Space Telescope is based on an existing 2.4 m (7.9 ft) wide field of view primary mirror and will carry two scientific instruments. The Wide-Field Instrument (WFI) is a 300.8-megapixel multi-band visible and near-infrared camera, providing a sharpness of images comparable to that achieved by the Hubble Space Telescope over a 0.28 square degree field of view, 100 times larger than imaging cameras on the Hubble. The Coronagraphic Instrument (CGI) is a high-contrast, small field of view camera and spectrometer covering visible and near-infrared wavelengths using novel starlight-suppression technology.
Stated objectives [ 6 ] include a search for extra-solar planets using gravitational microlensing , [ 7 ] along with probing the chronology of the universe and growth of cosmic structure, with the end goal of measuring the effects of dark energy , [ 8 ] the consistency of general relativity , and the curvature of spacetime .
Roman was recommended in 2010 by the United States National Research Council Decadal Survey committee as the top priority for the next decade of astronomy. On 17 February 2016, it was approved for development and launch. [ 9 ] On 20 May 2020, NASA Administrator Jim Bridenstine announced that the mission would be named the Nancy Grace Roman Space Telescope in recognition of former NASA Chief of Astronomy Nancy Grace Roman 's role in the field of astronomy . [ 10 ] As of May 2024 [update] , Roman is scheduled to be launched on a Falcon Heavy rocket under a contract specifying readiness by October 2026 [ 3 ] supporting a NASA launch commitment of May 2027. [ 11 ] [ 12 ]
The design of the Roman Space Telescope shares a heritage with various proposed designs for the Joint Dark Energy Mission (JDEM) between NASA and the Department of Energy (DOE).
The original design, called WFIRST Design Reference Mission 1, was studied in 2011–2012, featuring a 1.3 m (4.3 ft) diameter unobstructed three-mirror anastigmat telescope. [ 13 ] It contained a single instrument, a visible to near-infrared imager/slitless prism spectrometer.
In 2012, another possibility emerged: NASA could use a second-hand National Reconnaissance Office (NRO) telescope made by Harris Corporation to accomplish a mission like the one planned for WFIRST. NRO offered to donate two telescopes , the same size as the Hubble Space Telescope but with a shorter focal length and hence a wider field of view . [ 14 ] This provided important political momentum to the project, even though the telescope represents only a modest fraction of the cost of the mission and the boundary conditions from the NRO design may push the total cost over that of a fresh design. This mission concept, called WFIRST-AFTA (Astrophysics Focused Telescope Assets), was matured by a scientific and technical team; [ 15 ] this mission is now the only present NASA plan for the use of the NRO telescopes. [ 16 ] The Roman baseline design includes a coronagraph to enable the direct imaging of exoplanets . [ 17 ]
Several implementations of WFIRST/Roman were studied. These included the Joint Dark Energy Mission -Omega configuration, an Interim Design Reference Mission featuring a 1.3 m (4.3 ft) telescope, [ 18 ] Design Reference Mission 1 [ 19 ] with a 1.3 m telescope, Design Reference Mission 2 [ 20 ] with a 1.1 m (3.6 ft) telescope, and several iterations of the AFTA 2.4 m (7.9 ft) configuration.
In the 2015 final report, [ 6 ] Roman was considered for both geosynchronous orbit and for an orbit around the Sun-Earth Lagrange point L 2 . L 2 has disadvantages versus geosynchronous orbit in available data rate and propellant required, but advantages for improved observing constraints, better thermal stability, and more benign radiation environment. Some science cases (such as exoplanet microlensing parallax) are improved at L 2 , but the possibility of robotic servicing at either of the locations is currently unknown. By February 2016 it had been decided to use a halo orbit around L 2 . [ 9 ]
The project is led by a team at NASA's Goddard Space Flight Center in Greenbelt, Maryland . On 30 November 2018, NASA announced it had awarded a contract for the telescope. [ 21 ] This was for a part called OTA, the Optical Telescope Assembly, and runs to 2025. [ 21 ] This is in conjunction with the Goddard Space Flight Center, for which the OTA is planned for delivery as part of this contract. [ 21 ]
A February 2019 description of the mission's capabilities is available in a white paper issued by members of the Roman team. [ 22 ]
The science objectives of Roman aim to address cutting-edge questions in cosmology and exoplanet research, including:
The telescope is to carry two instruments.
On 2 March 2020, NASA announced that it had approved WFIRST to proceed to implementation, with an expected development cost of US$3.2 billion and a maximum total cost of US$3.934 billion, including the coronagraph and five years of mission science operations. [ 28 ]
On 20 May 2020, NASA Administrator Jim Bridenstine announced that the mission would be named the Nancy Grace Roman Space Telescope in recognition of the former NASA Chief of Astronomy's role in the field of astronomy . [ 10 ]
On 31 March 2021, the NASA Office of Inspector General (OIG) released a report that stated that the development of the Nancy Grace Roman Space Telescope had been affected by the COVID-19 pandemic , which hit the US during a particularly important time in the telescope's development. NASA is expecting a total impact of US$400 million due to the pandemic and its effect on subcontractors for the project. [ 29 ]
On 29 September 2021, NASA announced that Roman had passed its Critical Design Review (CDR), and that with predicted impacts from COVID-19 disruptions, and with flight hardware fabrication completed by 2024 followed by mission integration, the launch date would be no later than May 2027. [ 30 ]
On 19 July 2022, NASA announced that Roman would be launched on a Falcon Heavy launch vehicle, with a contract specifying readiness by October 2026 and a launch cost of approximately $255 million. [ 3 ]
In October 2024, the telescope passed a major ‘spin test’. [ 31 ]
In September 2024, the satellite bus which will carry the telescope, was substantially completed. [ 32 ] The following December, the instruments and mirror assembly were successfully integrated onto a section called the "instrument carrier". [ 33 ]
In the fiscal year 2014, Congress provided US$56 million for Roman, and in 2015 Congress provided US$50 million. [ 34 ] The fiscal year 2016 spending bill provided US$90 million for Roman, far above NASA's request of US$14 million, allowing the mission to enter the "formulation phase" in February 2016. [ 34 ] On 18 February 2016, NASA announced that Roman had formally become a project (as opposed to a study), meaning that the agency intends to carry out the mission as baselined; [ 9 ] at that time, the "AFTA" portion of the name was dropped, as only that approach is being pursued. Roman is on a plan for a mid-2020s launch. The total cost of Roman at that point was expected at more than US$2 billion; [ 35 ] NASA's 2015 budget estimate was around US$2.0 billion in 2010 dollars, which corresponds to around US$2.7 billion in real year (inflation-adjusted) dollars. [ 36 ]
In April 2017, NASA commissioned an independent review of the project to ensure that the mission scope and cost were understood and aligned. [ 37 ] The review acknowledged that Roman offers "groundbreaking and unprecedented survey capabilities for dark energy , exoplanet , and general astrophysics ", but directed the mission to "reduce cost and complexity sufficient to have a cost estimate consistent with the US$3.2 billion cost target set at the beginning of Phase B". [ 38 ] NASA announced (Jan 2018) the reductions [ clarification needed ] taken in response to this recommendation, and that Roman would proceed to its mission design review in February 2018 and begin Phase B by April 2018. [ 39 ] NASA confirmed (March 2018) that the changes [ clarification needed ] made to the project had reduced its estimated life cycle cost to US$3.2 billion and that the Phase B decision [ clarification needed ] was on track to begin on 11 April 2018. [ 40 ]
In February 2018, the Trump administration's proposed an FY2019 budget that would have delayed the funding of the Roman (then called WFIRST), citing higher priorities [ clarification needed ] within NASA and the increasing cost of this telescope. [ 41 ] The proposed defunding of the project was met with criticism by professional astronomers, who noted that the American astronomical community had rated Roman the highest-priority space mission for the 2020s in the 2010 Decadal Survey . [ 42 ] [ 43 ] The American Astronomical Society expressed "grave concern" about the proposed defunding, and noted that the estimated lifecycle cost for Roman had not changed over the previous two years. [ 44 ] In agreement, Congress approved a FY2018 Roman budget on 22 and 23 March 2018 in excess of the administration's budget request for that year, stated that it "rejects the cancellation of scientific priorities recommended by the National Academy of Sciences decadal survey process", and directed NASA to develop new estimates of Roman's total and annual development costs. [ 45 ] [ 40 ] The President of the United States announced he had signed the bill on 23 March 2018. [ 46 ] NASA was funded via a FY2019 appropriations bill on 15 February 2019, with US$312 million for Roman, rejecting the President's reduced Budget Request and reasserting the desire for completion of Roman with a planning budget of US$3.2 billion. [ 47 ]
In March 2019 the Trump administration again proposed to defund the Roman in its FY2020 budget proposal to Congress. [ 48 ] In testimony on 27 March 2019, NASA Administrator Jim Bridenstine hinted that NASA would continue Roman after the James Webb Space Telescope , stating "WFIRST will be a critical mission when James Webb is on orbit". [ 49 ] In a 26 March 2019, presentation to the National Academies' Committee on Astronomy and Astrophysics, NASA Astrophysics Division Director Paul L. Hertz stated that Roman "is maintaining its US$3.2 billion cost for now... We need US$542 million in FY2020 to stay on track". At that time, it was stated that Roman would hold its Preliminary Design Review (PDR) for the overall mission in October 2019 followed by a formal mission confirmation in early 2020.
NASA announced the completion of the Preliminary Design Review (PDR) on 1 November 2019, but warned that though the mission remained on track for a 2025 launch date, shortfalls in the Senate's FY2020 budget proposal for Roman threatened to delay it further. [ 50 ]
In April 2025, the second Trump administration proposed to cut funding for Roman again as part of its FY2026 budget draft. This was part of wider proposed cuts to NASA's science budget, down to US$3.9 billion from its FY2025 budget of US$7.5 billion. [ 51 ] On April 25, 2025, the White House Office of Management and Budget announced a plan to cancel dozens of space missions, including the Roman Space Telescope, as part of the cuts. [ 52 ]
The Roman project office is located at NASA's Goddard Space Flight Center in Greenbelt, Maryland , and holds responsibility for overall project management. GSFC also leads the development of the Wide-Field Instrument, the spacecraft, and the telescope. The Coronagraphic Instrument is being developed at NASA's Jet Propulsion Laboratory in Pasadena, California . Science support activities for Roman are shared among Space Telescope Science Institute ( Baltimore, Maryland ), which is the Science Operations Center; the Infrared Processing and Analysis Center , Pasadena, California; and GSFC .
Four international partners, namely the French space agency CNES , European Space Agency (ESA), Japan Aerospace Exploration Agency (JAXA), and the Max Planck Institute for Astronomy have joined with NASA to provide various components and science support for Roman. [ 53 ] [ 54 ] [ 55 ] Beginning in 2016 NASA expressed interest in ESA contributions to the spacecraft, coronagraph and ground station support. [ 56 ] For the coronagraph instrument, contributions from Europe and Japan have been established. [ 56 ] In 2018, a contribution from Germany 's Max Planck Institute for Astronomy was under consideration, namely the filter wheels for the star-blocking mask inside the coronagraph. [ 57 ] In 2016, the Japanese space agency JAXA proposed to add a polarization module for the coronagraph, plus a polarization compensator. An accurate polarimetry capability on Roman may strengthen the science case for exoplanets and planetary disks , which shows polarization. [ 58 ] [ 59 ] Ground support will be provided by a new NASA station in White Sands , the Misada station in Japan and ESAs New Norcia station in Australia. [ 60 ]
In May 2018, NASA awarded a multi-year contract to Ball Aerospace to provide key components (the WFI Opto-Mechanical Assembly) for the Wide-Field Instrument on Roman. [ 61 ] In June 2018, NASA awarded a contract to Teledyne Scientific and Imaging to provide the infrared detectors for the Wide-Field Instrument. [ 62 ] On 30 November 2018, NASA announced it had awarded the contract for Optical Telescope Assembly to the Harris Corporation of Rochester, New York . [ 21 ] | https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telescope |
The Nanjing Metro is a rapid transit system serving the urban and suburban districts of Nanjing , the capital city of Jiangsu Province in the People's Republic of China .
Proposals for a metro system serving Nanjing first began in 1984, with approval by the State Planning Commission granted in 1994. Construction began on the initial 16-station Line 1 in 1999, and opened in 2005. The system has 14 lines and 236 stations running on 521 km (324 mi) of track. It is operated and maintained by the Nanjing Metro Group Company. Future expansion plans include 30 lines set to open within the next few years, with several more awaiting approval to begin construction.
In 1984 the first serious proposal for construction of a subway appeared in the Municipal People's Congress. [ 5 ] In April 1986, the Nanjing Integrated Transport Planning group was established to research on how to implement a subway system in Nanjing. In December 1986 the team published the "Nanjing Metro Initial Phase". The phase consists of a north–south line , east–west line and a diagonal Northwest to Southeast line. The three lines meet in the city center forming a triangle. [ 6 ] A revision of the "Nanjing City Master Plan" in 1993 added another line through the urban core, and three light metro lines connecting Nanjing's suburbs in Pukou and the at time proposed new airport . In addition a suburban railway to Longtan was proposed. A 1999 report on "Nanjing city rapid rail transit network planning" further proposed six subway lines, two subway extensions and three light metro lines. [ 7 ]
In 1994, the State Planning Commission approved the preparatory work for the subway only to have the entire metro project postponed in 1995 amid a national freeze on new metro projects. [ 8 ]
Major changes were made to "Nanjing Urban Rail Transit Network Planning" in 2003. [ citation needed ] The new master plan consisted of 13 lines, of which nine are subway lines and four are light metro lines. The new Line 6 will be a loop line connecting all the urban radial lines. The plan retained the original lines 1, 2 and 3 from the previous plan. According to the new plan, the initial phase would consist of the completion of Metro Line 1 and 2 by 2010. Together the two lines will form a basic "cross" network. By 2020 the completion of Lines 1, 2, 3, and 4 was to form a more robust "pound" shaped (#) network. Longer-term plans include the construction of a loop line connecting all existing lines. The plan also identified four subway lines crossing the Yangtze river.
The initial section of Line 1 from Maigaoqiao to Xiaohang received final official approval in 1999. In May 2000, the Experimental Station resumed construction with the entire Line 1 project in full construction in December.
A western extension of Line 1 from Xiaohang to a newly built stadium was fast tracked after Nanjing won hosting the National Games . Line 1's initial section and the western extension started trial operations on September 3, 2005, running from Maigaoqiao to Olympic Stadium with 16 stations and a total length of 21.72 kilometers (13.50 mi). [ 5 ] The opening of the Nanjing Metro Line 1 gave Nanjing the sixth metro system in the Chinese mainland after Beijing, Tianjin, Shanghai, Guangzhou and Shenzhen.
Line 2 originated from the east-west line in the early planning stages, designed to connect the eastern Xianlin sub-city and western Hexi sub-city, with a plan to cross the Yangtze River. In December 2003, the construction of Olympic Stadium East station began, followed by the construction of experimental station Xinglongdajie (project name Suojie) started in December 2005. [ 9 ] In mid-2006, all 19 stations (from Youfangqiao to Maqun) from phase I started construction officially, with a total length of 25.27 kilometres.
The east extension of Line 2 was approved and commenced in October 2007, [ 10 ] adding 5 stations eastward from Maqun station to Yangshangongyuan station, and an additional 2 stations to Jingtianlu station later. However, due to the geological problems and the resulting accident encountered during the construction of Jingqingmendajie station, the original cross-river plan of Line 2, along with the proposed metro ring line (Line 6) were cancelled. The route of Line 2 had been changed to go south to the terminal station Youfangqiao. The new round of network planning and construction of Nanjing Metro was impacted significantly by this change. On May 28, 2010, the phase I and east extension of Line 2 opened simultaneously with 26 stations and a length of 37.80 kilometres from Jingtianlu to Youfangqiao.
The north extension of Line 1 connects main city and Jiangning district. The route starts from the northern side of the main city to the east-north direction to Dongshan, Jiangning via Nanjing South Railway Station. The construction of experimental station Hedingqiao began in November 2006, and the rest of the line started in the following year. The proposed extension included 12 new stations from Andemen to Longmiandadao, covering a distance of 18.01 kilometres. Another extension of this route was added with 3 new stations to the Jiangning university town in May 2008. On May 28, 2010, both the south extension of Line 1 and its own extension project entered service, starting from northern Andemen station to southern China Pharmaceutical University (CPU), bringing the total route length to 25.08 kilometres with 15 stations. The south extension of Line 1 is connected with Line 1, forming a Y-shaped bifurcation.
On May 28, 2010, the total operating mileage of Nanjing Metro increased to 84.75 kilometres after the opening of Line 2 and south extension of Line 1. Line 1, Line 1 south extension and Line 2 formed a cross-shaped network framework, marking Nanjing Metro’s entry into the era of networked operations.
Line 1 runs mainly in a north–south direction. The line starts at Maigaoqiao in the north, heading southwards to CPU (China Pharmaceutical University). The construction of Line 1 began in the year 2000 and was inaugurated on September 3, 2005, with 16 stations and a length of 21.72 kilometers (13.50 mi). [ 22 ] On May 28, 2010, Line 1's 24.5-kilometer (15.2 mi) long south extension entered into operation. [ 23 ] [ 24 ] Thus, before the transfer of Line 1's Olympic Stadium Branch to Line 10, Line 1 was 46.2-kilometer (28.7 mi) long with 31 stations. [ citation needed ] The Olympic Stadium branch line broke away from Line 1 and formed parts of Line 10, [ 25 ] when the latter's construction finished and entered operation on July 1, 2014. Currently, Line 1 is 38.9-kilometer (24.2 mi) long with 27 stations. [ 26 ] Line 1's color is light blue .
Line 2 is 43.4-kilometer (27.0 mi) long and has 30 stations. [ 12 ] It runs mainly in an east–west direction, from Yuzui in the southwest to Jingtianlu in the northeast. It entered into operation on May 28, 2010. [ 23 ] [ 24 ] On 28 December 2021, the line was extended west 5.4 kilometers (3.4 mi) with 4 new stations to Yuzui Station. [ 27 ] Line 2's color is red .
Groundbreaking work for Line 3 started in January 2010. This line, with a north–south orientation, started operation on April 1, 2015 [ 28 ] and is 44.9 kilometres (27.9 mi) in length with 29 stations. [ 13 ] Line 3's color is green .
Construction of east–west Line 4 begun in late 2012 [ 29 ] and the first phase entered operation on January 18, 2017. The completed portion is 33.75 kilometers (20.97 mi) in length. [ 30 ] The line is known as A Zi (the Purple) as the branding for the line and the train color is purple, the first of which were delivered in April 2015. [ 31 ] The line started operation on January 18, 2017. [ 32 ] Line 4's color is purple .
Line 5 opened its southern section on March 31, 2024 that is 12.9 kilometers long with nine stations. [ 33 ] Line 5's color is yellow .
Line 7 is a northeast–southwest line roughly following the south bank of the Yangtze River . [ 34 ] The south section has been under construction since November 2017. [ 35 ] The rest of the line started construction in November 2018. [ 36 ] The north section from Xianixnlu to Mufuxilu opened on 28 December 2022, [ 37 ] the south section from Yingtiandajie to Xishanqiao opened on 28 December 2023, and the central section from Mufuxilu to Yingtiandajie opened on 28 December 2024. This line is also the first line of Nanjing Metro to use trains in GoA4 automated level. Line 7's color is dark green .
Line 10 is a western extension from Line 1's Olympic Stadium branch line, which broke away from Line 1 and formed part of Line 10 when the new line was completed. Construction started in February 2012, [ 38 ] finished in 2014. The line is approximately 21.6-kilometer (13.4 mi) long with 14 stations, [ 15 ] and entered operation on July 1, 2014. [ 39 ] Line 10's color is beige .
Line S1 acts as Nanjing's airport express line, connecting Nanjing South Railway Station to Gaochun District via Nanjing Lukou International Airport . The entire line was planned to be 85.8-kilometer (53.3 mi) long with 13 stations. [ 40 ] The first phase from Nanjing South to Lukou International Airport started construction on December 27, 2011, and finished in 2014. The first phase opened on July 1, 2014, in time for the Nanjing 2014 Summer Youth Olympics . It is 35.8-kilometer (22.2 mi) long with 8 stations. [ 16 ] The second phase extension later became Line S9. [ 41 ] Line S1's color is teal .
Line S3 opened on 6 December 2017. It starts from Nanjing South Railway Station and heads west, crossing the Yangtze River on the cantilever along the edge of Dashengguan Yangtze River bridge together with high-speed rail trains, before terminating at the Gaojiachong station in Qiaolin, southwest of Pukou District. Originally planned as Metro Line 12 or the Ninghe Intercity Rail Line, the route started construction in late 2011. Besides Nanjing South Railway Station in which passengers can transfer to Lines 1, 3, or S1, Youfangqiao station is also a transfer station between Line S3 and Line 2. [ 42 ] [ 43 ] Phase one is 37.53 kilometers (23.32 mi) long with 19 stations [ 44 ] and connects Nanjing South Railway Station to Jiangbei New Area in Pukou. Phase 2 is now still being planned, which might extends further southwest from Phase 1 to Hexian county in the far future. [ 45 ] Line S3's color is magenta .
Line S4 or the Nanjing-Chuzhou Intercity Railway is a 46.2 kilometers (28.7 mi) rapid transit line connecting Nanjing North railway station with neighboring Chuzhou city in Anhui province. The line will feature passing loops at select stations to allow for distinct express and local services. [ 46 ] Chuzhou section of the line is opened on 28 June 2023. [ 47 ] An extension to Nanjing North railway station is under construction. The Chuzhou section of the line will use the separated "Chuzhou Rail Transit" logo. [ 48 ]
Line S6 or the Nanjing-Jurong Intercity Railway is a 43.7 kilometers (27.2 mi) connecting suburban Nanjing with neighboring Jurong opened on 28 December 2021. It is the first line in Nanjing Metro that reaches other cities, starting at Maqun station , ending at Jurong station . Line S6's color is lilac .
Line S7 opened on 26 May 2018. It is an extension of Line S1 further southeast, starting at Konggangxinchengjiangning station , ending at Wuxiangshan station in South Lishui District . Some Line S1 trains continue to operate into Line S7. Line S7's color is pink .
Line S8 is a suburban metro line which connects Luhe District to Pukou District . The line is 45.2 kilometers (28.1 mi) long, [ 20 ] 34.1 kilometers (21.2 mi) of the line is elevated. The line features 17 stations [ 20 ] including 6 underground stations and 11 elevated ones. It uses B size trains in 4 car sets that are capable of running up to 100 kilometers per hour (62 mph). Construction of the line started on June 21, 2012, and it was officially opened on August 1, 2014. [ 49 ] [ 50 ] Line S8's color is orange .
Line S9 starts from Xiangyulunan station , the 6th station from Nanjing South Railway Station on Line S1, and extends further south to Gaochun District for a total length of 52.42 km (32.57 mi). Upon opening on December 30, 2017, Nanjing became the first city in mainland China where every district is accessible by metro. [ 51 ] Line S9's color is yellow .
Line 5 received approval on 14 January 2015. [ 63 ] Before the relocation in 2017, the line is projected to be 37.4 kilometers (23.2 mi) long, containing 30 stations and to cover a route from Fangjiaying station in Gulou District to Jiyindadao station in Jiangning District . [ 64 ]
Line 6 is a 32.4 km fully underground line with 19 stations. Construction started on 28 December 2019. [ 65 ]
Line 9 (Phase 1) is a 19.67 kilometers (12.22 mi) have a total of 16 stations, all of which are underground. The symbol of the train is orange red, and the maximum speed is 80 km/h. The route passes through Xuanwu District , Gulou District and Jianye District, and passes through Nanjing Railway Station, Xiaguan, Longjiang, Lüboyuan , Jiangsu Grand Theater and other areas. In the future, it will become an important line within the main city to connect the central Hexi, Xiaguan and Xinzhuang areas. The regional line is of great significance to the development of Hexi New City and the upgrading and reconstruction of the Xiaguan area. Construction started in May 2020, the construction period is about 4 years. [ 66 ] The list of stations: Danxialu, Caohouxun, Nanjing Railway Station, Zhongyangmen, Chenghecun, Daqiaonanlu, Xiaguan, Agricultural Trade Centre, Dinghuaimendajie, Longjiang, Guanziqiao, Hanzhongmendajie, Shuiximendajie, Qinghelu, Lüboyuan and Binjianggongyuan. [ 67 ] In the southern extension of Phase 2, Line 9 is expected to be extended all the way to Banqiao in the far south west of Nanjing.
The Nanjing Metro Phase III construction plan was submitted to the National Development and Reform Commission in 2024. [ 68 ] The plan proposed 10 projects which include: 2 new lines, 7 extensions of existing lines and 1 shuttle line totalling 120 km of new metro. The Nanjing Metro Phase III construction plan proposed Line 2 East Extension, 2-9 Shuttle Line, Line 3 Phase IV, Line 4 Phase III West Extension, Line 4 Phase III East Extension, Line 8 Phase I, Line 9 Phase II, Line 10 Phase III, Line 16 and Line S3 East Extension to be constructed. [ 69 ]
Fares on the Nanjing Metro are distance-based. Fares range from 2 yuan (approx US$0.30) for journeys under 4 kilometers, to 15 yuan for longer journeys. [ 70 ] There is a 5% discount for users of the Nanjing Public Utility IC Card. Fares can also be paid using Alipay, but with no discount. [ 71 ]
Single journey tickets can be purchased from the ticket vending machine or at a ticket window. The ticket vending machine accepts both coins, bills (¥5 and ¥10) and Alipay. [ 72 ]
Apart from one-way tickets, fares can be paid with the Nanjing Public Utility IC Card, or Jinlingtong ( Chinese : 金陵通 ; pinyin : Jīnlíngtōng ). It can be purchased for a refundable fee of 25 yuan (about 3.8 dollars) and refilled at ticket booths inside the metro stations as well as many collaborative convenience stores throughout the city. The card can be used to pay for other means of public transportation, such as the city taxi and the city bus. An NFC version of the card is free of charge by applying from the iPhone 's Wallet app.
This transit card is similar to Beijing 's Yikatong , and the Octopus card of Hong Kong 's MTR .
Since April 1, 2025, Nanjing Metro has offered a metro pass with options for a 1-day pass (¥20, approximately US$2.80) and a 3-day pass (¥45, approximately US$6.20). The pass allows unlimited metro rides within the designated time period. Both passes are available for purchase at selected metro stations, including those near tourist attractions, central business districts (CBDs), and major transportation hubs. [ 73 ]
For Line 1, Siemens Transportation Systems (TS) was awarded the supply contract in November 2002.
For Line 2, Siemens Transportation Systems (TS) and its local partner Nanjing Research Institute of Electronic Technology (NRIET) have been awarded to supply the signaling system after signing a contract (about 25 million Euro). Technologies used include Trainguard MT, Vicos OC 501, Sicas ECC and Az S 350 U axle counting system. [ 77 ]
[ needs update ]
a Discrepancies between these figures are explained by interchange stations. If interchange stations are counted once for each line they serve, there would be 114 urban line stations, 50 S-line stations, and 164 total stations. | https://en.wikipedia.org/wiki/Nanjing_Metro |
Nano Angle-Resolved Photoemission Spectroscopy (Nano-ARPES) , is a variant of the experimental technique ARPES (Angle-Resolved Photoemission Spectroscopy). It has the ability to precisely determine the electronic band structure of materials in momentum space with submicron lateral resolution. Due to its demanding experimental setup, this technique is much less extended than ARPES, widely used in condensed matter physics to experimentally determine the electronic properties of a broad range of crystalline materials. Nano-ARPES can access the electronic structure of well-ordered monocrystalline solids with high energy, momentum, and lateral resolution, even if they are nanometric or heterogeneous mesoscopic samples. Nano-ARPES technique is also based on Einstein's photoelectric effect , being photon-in electron-out spectroscopy, which has converted into an essential tool in studying the electronic structure of nanomaterials, like quantum and low dimensional materials. [ 1 ] [ 2 ]
NanoARPES allows to determine experimentally the relationship between the binding energies and wave momenta of the electrons of the occupied electronic states of the bands with energies close and approximately 10-15 eV below the Fermi level. [ 1 ] These electrons are ejected from a solid when it is illuminated by monochromatic photons with sufficient energy to emit photoelectrons from the surface of the material. These photoelectrons are detected by an electron analyzer placed close to the samples surface in vacuum to preserve the uncontaminated surfaces and to avoid the collisions with particles able to modify the energy and trajectory of the photoelectrons in their way to the spectrometer. As in the photoemission process, the momentum is conserved; therefore, the angular distribution of photoelectrons from a monocrystal, even if it is a nanometric size, is also enabled to directly reveal the momentum distribution of initial electronic states in that crystal. The Nano-ARPES results, as in the ARPES technique, are traditionally shown as energy-momentum dispersion relation along the high symmetry directions of the irreducible Brillouin Zone , displaying the band dispersions of the investigated materials. [ 3 ] [ 4 ] When the emitted photoelectrons are shown by constant energy surfaces throughout large portions of the reciprocal space, Nano-ARPES can also precisely determine the Fermi surface of the investigated materials. Due to the unique ability to spatially map the electronic dispersion of the electrons in the samples, Nano-ARPES can also generate electronic imaging of nanomaterials with high binding energy and momentum resolution. As Nano-ARPES is a scanning technique, [ 5 ] it can use state-of-the-art ARPES spectrometers without requiring them to be able also to discriminate spatially the origin of the analysed photoelectrons. Consequently, Nano-ARPES instrumentation can profit from the most advanced spectrometers developed for ARPES setups, particularly those of the latest generation electron spectrometers with bidimensional detection and high energy and momentum resolution. [ 6 ] [ 7 ]
The comprehension of the electronic band structure of solids is applied in many fields of condensed matter physics, contributing to the microscopic understanding of many phenomenological trends and guiding the interpretation of experimental spectra in photoemission, optics, inelastic neutron scattering, specific heat, among others, including the effect of spin-polarisation. Most modern band electronic structure theoretical methods employ Density Functional Theory to solve the full many-body Schrödinger equation for electrons in a solid. The consolidated experimental and theoretical approach to describe the electronic structure of solids allows the straightforward visualization of the difference between conductors , insulators , and semiconductors according to the presence of permitted and forbidden electronic states of particular energy and momentum, which can be calculated by quantum mechanics and measured using ARPES. [ 8 ]
The ARPES technique has the unique ability to determine the band structure directly. It thus helps understand the degree and type of electron interaction in the solids, corroborating or contesting band electronic structure results calculated using different theoretical approaches. However, this technique's lateral resolution, manipulation, and orientation of submicrometric of heterogeneous samples are rather limited. That is because the electrons measured in ARPES are all those electrons ejected by the photo-absorption process prompted by the incident photons. If the illuminated area of the sample is large enough to cover nonhomogeneous areas, the detected ejected electrons are the sum up of all the photoelectrons emitted by all different illuminated patches. If each area has a distinctive electronic band structure, the ARPES spectra will show the average of all of them weighted according to the size of each different patch present in the illuminated area. [ 9 ]
In fact, many complex materials are constituted by disoriented small monocrystals or composed of several nanometric monocrystals. Traditional ARPES can only provide their average electronic structure if the patch size is smaller than the spot size of the ARPES setup, typically 200 um. This limitation is also present in samples with micrometric and submicrometric zones with distinctive chemical composition due to undesired side chemical reactions, for example, originating by the contamination or oxidation of the primitive sample. Hence, being the spot size of the monochromatic photon beam typically over 200 ųm side for conventional ARPES, only homogeneous samples with this size or bigger can be studied.
Consequently, a sub-micrometric lateral resolution should be added to ARPES to perform the experimental determination of the electronic structure of small crystalline materials and large samples with heterogeneities. Nano-ARPES has implemented this lateral discrimination by focalising the size of the photon incident beam within the nanometric scale. Similarly to ARPES, the electronic band structure of nanomaterials can be directly measured using Nano-ARPES by measuring the ejected electrons' kinetic energy, velocity, and absolute momentum. [ 10 ]
The photon beam focusing to a spot size down to nanometric scale has been routinely achieved in a few well-known X-ray-based methods, such as scanning transmission X-ray microscopy (STXM) and scanning photoemission microscopy (SPEM). [ 11 ] However, these techniques are much less demanding because they typically use incident photon energies higher than 150 eV and require non-angle resolved measurements, only recording integrated signals proportional to the X-Ray absorption coefficient and core-level photoelectrons, respectively. In both cases, the Fresnel Zone Plates (FZPs) performance is the essential component determining the lateral resolution, varying from micro- to nanometric lateral resolution. Nowadays, several companies in the market provide FZPs with a resolution better than 30 nm, which has facilitated the construction and operation of several x-Ray based microscopes such as STXM and SPEM instruments in different synchrotron radiation facilities like Elettra , ALS , CLS, [ 12 ] and MAX-lab, [ 13 ] among others. Nano-ARPES technique, however, requires much lower incident photon energy, typically from 6 eV to 100 eV) to detect those photoelectrons emitted by the electronic states below and close to the Fermi level, which cross-section increases as the incident photon energy decreases. [ 14 ] [ 15 ] An alternative k-space imaging approach is based on energy-filtered photoemission microscopes ( PEEMs ), The lateral resolution is achieved using an electron optical column instead of focalizing the incident photon beam. This full-field k-space version of PEEM is available commercially. However, for this commercially available full-field PEEM version with k-space imaging, achieving high energy and momentum resolution is challenging. [ 16 ]
Typically, high energy and momentum resolution ARPES experiments are performed at synchrotrons , which can provide bright and tunable high-energy photons sources to record the electronic band structure of ordered materials directly. That yields sharp and precise E vs k dispersions and constant energy surfaces, including those corresponding to the Fermi surface of the studied materials.
The conventional ARPES systems consist of a monochromatic light source to deliver a narrow beam of photons, a sample holder connected to a manipulator used to position the samples angular and translationally concerning the electron spectrometer (detector), and the incident light beam focus. The equipment is contained within an ultra-high vacuum (UHV) environment, which protects the sample from undesired contamination and prevents scattering of the emitted electrons. After being dispersed along two perpendicular directions for kinetic energy and emission angle, the electrons are directed to the detector and counted to provide ARPES spectra-slices of the band structure along one momentum direction. [ 10 ] [ 17 ] [ 18 ]
The main difference of its typical instrumental setup from other conventional ARPES apparatus is that the soft x-ray beam is focused to a submicrometric spot using Fresnel Zone plates (FZP) lenses. The specimens can be mounted on a high-precision manipulator that ensures the nanoscale sample positioning in the x, y, and z directions, where the polar angle (Θ) and the azimuthal angle (Ψ) can also be automatically scanned. [ 17 ] [ 19 ]
This basic instrumentation allows two operating modes: Nano-ARPES punctual mode (operating mode type 1) with nano-spot that maps the band structure of nanometric crystalline solids to study quasiparticle dynamics in highly correlated and non-correlated materials as in conventional ARPES, and Nano-ARPES imaging mode (operating mode type 2) that measures the spatial distribution in real space of photoelectrons of a selected binding energy and momentum values range. [ 4 ] [ 6 ]
State-of-the-art Nano-ARPES microscopes are equipped with continuous interferometric control of the position of the samples for the FZPs, which avoids thermal and mechanical drifts. That is required to prevent undesirable distortions of the recorded Nano-ARPES images (operating mode type 2) and precision and reproducibility of E vs. k dispersion curves along specific directions of the reciprocal space.
In the Nano-ARPES setups, the used analyzers are the hemispherical electron energy typically installed in high energy and angular resolution conventional ARPES apparatus. They use a slit to prevent the mixing of momentum and energy channels and, consequently, can only take angular maps in one direction. To record maps over energy and two-dimensional momentum space as in conventional ARPES, either the sample needs to be rotated, or the collected photoelectrons beam should be discriminated inside the spectrometer with the electrostatic lens, keeping the sample fixed. The energy-angle-angle maps are converted to binding energy-k//x-k//y maps. These images display constant energy surfaces as a function of the reciprocal space's k//x and k//y waves vectors. The most remarkable constant energy surface is the Fermi surface map, obtained by detecting those photoelectrons with binding energy right at the Fermi level. [ 20 ]
The Nano-ARPES technique is an essential tool to resolve the electronic band structure of mesoscopic or heterogeneous materials [ 21 ] in diverse condensed Matter fields like quantum materials [ 22 ] [ 23 ] high-temperature superconductors, topological materials [ 24 ] [ 25 ] semiconductors metals, [ 26 ] [ 27 ] insulators with not-too-large band gap and in a wide variety of low dimensional materials [ 28 ] [ 29 ] and heterostructures [ 30 ] [ 31 ] with effects of confinements, [ 32 ] [ 33 ] different stackings [ 34 ] [ 35 ] and hybridization. Also, electronic structure changes associated with all types of phase transitions, charge density waves, [ 36 ] bands hybridization [ 37 ] [ 38 ] phase separation, [ 39 ] charge transfer, and in-operando devices can be revealed by combining nano-lateral resolution with high energy and momentum resolution. [ 40 ] | https://en.wikipedia.org/wiki/Nano-ARPES |
The Nano-Japan Astrometry Satellite Mission for Infrared Exploration ( Nano-JASMINE ) is an astrometric microsatellite developed by the National Astronomical Observatory of Japan , with contributions by the University of Tokyo 's Intelligent Space Systems Laboratory (ISSL). As of 2015 [update] , the satellite was planned for launch together with CHEOPS (Characterizing Exoplanets Satellite) [ 3 ] [ 4 ] in 2019. [ 5 ] However, this launch took place in December 2019 without Nano-JASMINE as one of the three piggyback payloads. Some sources named 2022 as the launch year of the satellite. [ 6 ] By 2023, the launch had been cancelled and the satellite is now displayed in Kakamigahara Air and Space Museum . [ 7 ]
Nano-JASMINE is a microsatellite measuring 50.8 × 50.8 × 51.2 cm (20.0 × 20.0 × 20.2 in) and weighing approximately 35 kg (77 lb). [ 1 ] It carries a small, 5.25 cm (2.07 in) Ritchey–Chrétien telescope that will make observations in the infrared spectrum, allowing for easier observation toward the centre of the Milky Way . [ 2 ] Its exterior is covered with Gallium arsenide (GaAs) solar cells providing approximately 20 watts of power. [ 1 ] Due to limited bandwidth, Nano-JASMINE will employ a Star Image Extractor (SIE) for onboard raw image processing that will extract and transmit only specific object data. [ 8 ]
Nano-JASMINE is Japan's first and the world's third astrometric survey spacecraft, following Hipparcos (1989) and Gaia (2013), both launched by the European Space Agency (ESA). It is the pathfinder in a planned series of three spacecraft of increasing size and capability; the second is (originally and officially still called "Small-JASMINE") with a 30 cm (12 in) telescope, and the third is JASMINE with an 80 cm (31 in) telescope. [ 9 ] [ 10 ]
The spacecraft is designed to have an astrometric accuracy (2–3 mas (milli-arcsecond) for stars brighter than 7.5 magnitude ) comparable to Hipparcos (1 mas). Nano-JASMINE should be able to detect approximately four times the number of stars as Hipparcos. Given the time difference between these missions, combining the data sets of Nano-JASMINE and Hipparcos will constrain the positions of stars whose current positions are poorly known owing to uncertainty in their motion since being measured by Hipparcos, and should provide an order-of-magnitude increase in the accuracy of proper motion measurements (approximately 0.1 mas/year; 0.2 mas/year for stars brighter than 9 magnitude). [ 2 ]
Nano-JASMINE had been scheduled for launch aboard a Tsyklon-4 launch vehicle from the Brazilian Space Agency 's Alcântara Launch Center (CLA). The launch was originally contracted for August 2011, [ 11 ] but was delayed to the November 2013 to March 2014 time frame. [ 2 ] [ 9 ] Various issues have held back its launch, first due to delays in both the construction of the launch site and development of the launch vehicle, and later due to Brazil backing out of the Tsyklon-4 partnership with Ukraine leading to the rocket's indefinite hold. [ 12 ] [ 13 ] In March 2015, talks to arrange a flight for Nano-JASMINE began between NAOJ and ESA. [ 3 ] It was to be launched as a piggyback payload with CHEOPS on a Soyuz launch vehicle [ 4 ] [ 14 ] in 2019. [ 5 ] [ 15 ] As of late 2020, the launch of Nano-JASMINE was scheduled for 2022. In 2023, the launch was cancelled and the satellite was put on permanent display. [ 7 ]
Nano-JASMINE will be succeeded by a larger spacecraft, JASMINE (formerly "Small-JASMINE"), which is planned to be launched in 2028 by an Epsilon launch vehicle . [ 16 ] | https://en.wikipedia.org/wiki/Nano-JASMINE |
A nano-abacus is a nano-sized abacus that performs basic arithmetic computations using various forms of nanotechnology including photonics and lateral mechanical stimulation of molecular motion with a scanning tunneling microscope (STM) tip by repulsion . The nano-abacus has the potential to be used in a variety of nanotechnological inventions such as the nano-computer .
The first nano-abacus was developed on November 13, 1997 by physicist James Gimzewski at an IBM research laboratory in Zürich, Switzerland . Gimzewski's initial idea for the device was inspired by the Japanese soroban . [ 1 ] [ 2 ] The creation of the nano-abacus was sponsored by the Swiss Federal Office of Education and Science within the European Strategic Program for Research in Information Technology (ESPRIT) of the European Union as part of IBM's "PRONANO" (processing on the nanometer scale) project. [ 3 ]
Gimzewski's nano-abacus consists of stable rows containing ten molecules acting as railings. The beads are made up of buckminsterfullerene constrained by one-atom-high ridges on a copper sheet and are pushed around by the tip of a scanning tunneling microscope at room temperature to create a calculation and allow it be viewed when operated in imaging mode. [ 3 ]
Gimzewski, along with physicists Maria Teresa Cuberes and Reto R. Schlittler, found that their device was capable of controllably repositioning C60 molecules with a scanning tunneling microscope tip along Cu(111) mono-atomic steps at room temperature. [ 4 ]
A similar nanoscopic optical abacus was developed in 2017 by a team of international researchers led by Professor C. David Wright from the University of Exeter . The team's chip-scale all-optical abacus uses picosecond light pulses to perform arithmetic computations. The device has proved successful in calculating with multi-digit numbers using equivalent photonic phase-change cells. [ 5 ] [ 6 ]
This nanotechnology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nano-abacus |
Bones are the skeleton of our bodies. They allow us the ability to move and lift our body up against gravity . Bones are attachment points for muscles that help us to do many activities such as walking, jumping, kneeling, grasping, etc. Bones also protect organs from injury. Moreover, bone is responsible for blood cell production in a humans body.
The mechanical properties of bone greatly influence the functionality of bone. For instance, deterioration in bone ductility due to diseases such as osteoporosis can adversely affect individuals’ life. Bone ductility can show how much energy bone absorbs before fracture . In bone , the origin ductility is at the nanoscale. The nano interfaces in Bone are the interface between individual collagen fibrils . The interface is filled with non-collagenous proteins, mainly osteopontin (OPN) and osteocalcin (OC). [ 1 ] The osteopontin and osteocalcin form a sandwich structure with HAP minerals at nano-scale. The nano Interfaces are less than 2 – 3 % of bone content by weight, while they add more than 30% of the fracture toughness . [ 2 ] [ 3 ]
The current knowledge of the structure and deformation mechanisms in nano-interfaces is limited. [ 4 ] For the first time, a study [ 5 ] unravel the complex synergic deformation mechanism in the nano-interfaces in bone . A synergistic deformation mechanism of the proteins through strong anchoring and formation of dynamic binding sites on mineral nano-platelets were seen. The nano-interface can sustain a ductility approaching 5000% and outstanding specific energy to failure that is several times larger than the most known tough natural materials such as spider silk. | https://en.wikipedia.org/wiki/Nano-interfaces_in_bone |
Nano-scaffolding or nanoscaffolding is a medical process used to regrow tissue and bone, including limbs and organs. The nano-scaffold is a three-dimensional structure composed of polymer fibers very small that are scaled from a Nanometer (10 −9 m) scale. [ 1 ] Developed by the American military , the medical technology uses a microscopic apparatus made of fine polymer fibers called a scaffold. [ 2 ] Damaged cells grip to the scaffold and begin to rebuild missing bone and tissue through tiny holes in the scaffold. As tissue grows, the scaffold is absorbed into the body and disappears completely.
Nano-scaffolding has also been used to regrow burned skin. The process cannot grow complex organs like hearts. [ 3 ]
Historically, research on nano-scaffolds dates back to at least the late 1980s when Simon showed that electrospinning could be used to produce nano- and submicron-scale polymeric fibrous scaffolds specifically intended for use as in vitro cell and tissue substrates. This early use of electrospun fibrous lattices for cell culture and tissue engineering showed that various cell types would adhere to and proliferate upon polycarbonate fibers. It was noted that as opposed to the flattened morphology typically seen in 2D culture, cells grown on the electrospun fibers exhibited a more rounded 3-dimensional morphology generally observed of tissues in vivo . [ 4 ]
Nano-scaffolding is very small, 100 times smaller than the human hair and is built out of biodegradable fibers. The use of this scaffolding allows more effective use of stem cells and quicker regeneration. Electrospun nanofibers are prepared using microscopic tubes that range between 100 and 200 nanometers in diameter. These entangle with each other in the form of a web as they're produced. Electrospinning allows the construction of these webs to be controlled in the sense of the tube's diameter, thickness, and the material being used. [ 5 ] Nano-scaffolding is placed into the body at the site where the regeneration process will occur. Once injected, stem cells are added to the scaffolding. Stem cells that are attached to a scaffold are shown to be more successful in adapting to their environment and performing the task of regeneration. The nerve ends in the body will attach to the scaffolding by weaving in-between the openings. This will cause them to act as a bridge to connect severed sections. Over time the scaffolding will dissolve and safely exit the body leaving healthy nerves in its place.
This technology is the combination of stem cell research and nanotechnology . The ability to be able to repair damaged nerves is the greatest challenge and prize for many researchers as well as a huge step for the medical field. [ 6 ] This would allow doctors to repair nerves damaged in an extreme accident, like third degree burns. The technology however, is still in its infancy and is still not capable of regenerating complex organs like a heart, although it can already be used to create skin, bone and nails. [ 7 ] Nano scaffolding has been shown to be four to seven times more effective in keeping the stem cells alive in the body, which would allow them to perform their job more effectively. This technology can be used to save limbs that would otherwise need amputation. [ 8 ] Nanoscaffolding provides a large surface area for the material being produced, along with changeable chemical and physical properties . This allows them to be applicable in many different types of technological fields. [ 5 ]
Tissue engineering consists of the use of cells, scaffolds, and varying tissue architecture techniques to restore, replace, and regenerate damaged body tissue. [ 9 ] The goal of tissue engineering is to restore, replace, or regenerate damaged body tissue. [ 9 ] Nano-scaffolds along with cells and growth factor signals are utilized in tissue engineering applications. [ 9 ] Tissue engineering applications are designed to overcome hurdles associated with allotransplantation , which include unavailable donors, complex surgeries, and postoperative care. [ 10 ] In 2015, the tissue engineering global market was estimated at $23 billion, and expected to reach $94.2 billion by 2022. [ 10 ] The anticipation of fast growth was due to an increase in bone and joint disorders, with musculoskeletal regenerative medicines comprising 26.4% of the regenerative medicine market. [ 10 ]
Most human cells within tissues anchor to the solid extracellular matrix (ECM). [ 9 ] ECM components vary between various types of body tissues. [ 9 ] The ECM acts as a natural "scaffolding". [ 9 ] The ECM has five major function: [ 9 ]
The goal of the nano-scaffold is to mimic the ECM functions to encourage tissue restoration, replacement, and regeneration. [ 9 ] Both ECM variations between tissue types and the complexity of the ECM make nano-scaffold mimicry difficult. [ 9 ]
In order to mimic the ECM, the nano-scaffold follows four main features and functions: [ 9 ]
There are four major nano-scaffolding approaches, which include pre-made porous scaffolds for cell seeding, decellularized ECM from allogeneic or xenogeneic tissues for cell seeding, cell sheets with self-secreted ECM, and cell encapsulation in a self-assembled hydrogel matrix. [ 9 ] Each approach contains varying materials, fabrication methods, and resulting mechanical properties. In addition to these four approaches, metallic nano-particles have been researched to enhance the mechanical properties of nano-scaffolds. [ 11 ] Nanofiber electrospinning is another fabrication method for nano-scaffolding. [ 10 ]
Source: [ 9 ]
A wide array of nano-scaffold biomaterials have been used for pre-made porous scaffolds for cell seeding. These biomaterials can be classified as either natural or synthetic. Natural biomaterials are obtained from natural sources, which include but are not limited to, ECM from allografts or xenografts, calcium phosphates, and organic polymers, such as proteins, polysaccharides, lipids, and polynucleotides. Natural biomaterials increase nano-scaffold biocompatibility, but limit physical and mechanical stability. Natural biomaterials risk a negative immune response in the implantation host due to the allogeneic or xenogeneic source. Synthetic biomaterials can be subclassified as organic or inorganic. Compared to natural, synthetic biomaterials are more easily tailored to varying tissue hardness, and therefore are applicable to a wider variety of tissues. Synthetic biomaterials are less biocompatible and result in decreased cell attachment and growth. Surface and bulk properties can be altered within a synthetic biomaterials in an attempt to increase the biocompatibility of a surface.
Various fabrication techniques have been employed to fabricate a porous scaffold, such as porogens within biomaterials, solid free-form or rapid prototyping, and utilizing woven or non-woven fibers. To employ porogens in the nano-scaffold biomaterial, solid materials in solids or dissolved in solvents are combined with the porogen. Porogens include carbon dioxide, water, and paraffin. One the biomaterial is fabricated, the porogens are removed with methods such as sublimation, evaporation, and melting. Therefore, when the porogens are removed the porous scaffold is left behind with pores. To fabricate with solid free-form or rapid prototyping, methods such as laser sintering, stereolithography, and 3D printing have been utilized. These methods use light or heat transfer to bond or crosslink the biomaterial being used. Cross-linking provides enhanced material strength. The fabrication technique utilizing woven and non-woven fiber structures provides a porous structure when the fibers are bonded with thermal energy. Electrospinning is utilized via application of high voltages in a polymer solution. A spinning fiber jet is formed when the electrostatic forces surpass the forces within the polymer solution. The pre-made porous scaffolding method allows for a defined structure formation. With fabricating allowing an intricate structure formation, the nano-scaffolds utilizing this method can be tuned to resemble specific tissue ECMs.
Decellularized ECM from allogeneic and xenogeneic tissues have been utilized in tissue engineering for heart valves, vessels, nerves, tendons, and ligaments. To utilize the ECM from allogeneic or xenogeneic tissues the cellular antigens must be removed due to implant recipient immune response. Decellularization is conducted with a combination of physical, chemical, and enzymatic processes. Freeze-thaw cycles or ionic solutions have been utilized to lyse cell membranes. Trypsin/EDTA treatments are then utilized to separate ECM cellular components. Detergents solubilize and remove cell cytoplasm's and nuclei. The decellularized ECM with preserved growth factors is utilized as the nano-scaffold. Decellularized ECM nano-scaffolding provides mechanical properties closer to natural values than other methods due to utilizing a natural ECM structure. [ 9 ]
In the cell sheet approach, cells are utilized to secrete an ECM for scaffolding. Cells are cultured until confluence on a thermo-responsive polymer. Hydrophobicity is thermally-regulated repeatedly to detach multiple cell sheet layers. Loading capabilities of this approach are limited due to the use of thin cell sheets. Cell sheets with self-secreted ECM provide a high cell density and tight cell association within the nano-scaffold. [ 9 ]
The hydrogel structure consists of cross-linked hydrophilic polymer chains. A semi-permeable membrane or a homogeneous solid mass encapsulate cells. Natural and synthetic hydrogels are used to encapsulate the cells. Algae and sodium alginate provide a commonly used source for polysaccharides. Other natural biomaterials utilized include agarose and chitosan. Synthetic biomaterials include poly(ethylene glycol) (PEG) and polyvinyl alcohol (PVA). Prior to initiation, the biomaterials exist as a liquid monomer. The biomaterials are mixed with cells. Once initiated by pH, temperature, ionic strength, or light control, the biomaterials self-assembles into a solid polymer meshwork. Since the cells are mixed before initiation, this allows for the fabrication of the nano-scaffold construct, and cell seeding in one step. This method contains low mechanical properties due to the highly moldable structure of the nano-scaffold and is not ideal for load-bearing applications. [ 9 ]
Metallic nanoparticles within polymers increase mechanical strength and biocompatibility of nano-scaffolds. Copper, gold, iron oxide, platinum, palladium, strontium, titanium, zinc, and their oxides have been utilized in bone tissue regenerative applications. These nano-particles have been incorporated within polymers such as poly (lactic-co-glycolic acid) (PLDA), poly (L-lactic acid) (PLLA), poly (caprolactone (PCL), collagen, hyaluronic acid, silk, alginate, and fibrin. Copper nanoparticles within nano-scaffolding enhances antioxidant and anti-diabetic activities. Copper nanoparticles within nano-scaffolding can stimulate angiogenesis, cell migration, and proliferation of endothelial cells. Gold nanoparticles within nano-scaffolding induces osteogenic differentiation due to signal transduction from mechanical stimuli. Platinum nanoparticles and palladium nanoparticles within nano-scaffolding reduces oxidative stresses which decreases disease progression. Silver nanoparticles within nano-scaffolding are antimicrobial and aid in preventing postoperative pathogenic infections. Silver nanoparticles within nano-scaffolding have been used to develop microbe resistant coating. Titanium nanoparticles within nano-scaffolding are highly porous, which is ideal for cell proliferation. Zinc nanoparticles within nano-scaffolding decrease the number of reactive oxygen species, which are associated with failure of implants due to bacterial infection. [ 11 ]
Electrospinning systems consist of high voltage power, material delivery, and fiber collection units. The high voltages produce charged polymer solution, which exits from the delivery unit in a jet form. The jet of polymer solution is elongated and the solvent either evaporates or solidifies. Fibers are then collected in the collection unit. Flat plated are utilized to randomly collect the fibers. Rotors are utilized to rotate the collector to collect aligned fibers. Concentric collectors are utilized to collect the fibers in a disc, drum, or cone shape. Compared to random fibers, aligned fibers enhance integrin signaling pathways, and contain anisotropic properties similar to ECMs characterized by high degrees of orientation. Fibers may be fabricated from natural and synthetic polymers, including collagen, gelatin, elastin, silk, poly(l-lactic acid) (PLLA), ploy(glycolic acid) (PGA), poly(ԑ-caprolactone) (PCL), and poly(lactic-co-glycolic) acid (PLGA). The morphology of fibers fabricated through electrospinning varies with the solution properties of the polymer, hydrostatic pressure, temperature, and humidity. Nanofiber electrospinning can create loosely connected porous nanofiber mats, which can be fabricated with varying patterns for varying applications. Electrospinning nanofibers limits the three-dimensional capabilities of the nano-scaffold, which decreases cell differentiation and gene expressions. Three-dimensional electrospun scaffolds have been created by stacking multiple layers and then seeding cells within the scaffold. [ 10 ]
With the new advancement in nanotechnologies, there are many methods of fabrication that improve upon the methods previously mentioned . To appropriately emulate the complexity of native tissue and extracellular matrix(ECM) architecture, the adoption of nanotechnology becomes an integral part of scaffold implant production. [ 12 ]
Source: [ 12 ]
In 1936, Norton patented the first blow spinning device, most recently in 2015 research was published describing a device with concentric nozzles where a polymer solution was inserted into a stream of flowing gas in order to form nano-fibers from polymers like polystyrene. The new developments lead to the technique of airbrushing for nano-scaffold fabrication.
Airbrushing is a technique for fiber fabrication that involves two parallel concentric fluid streams; a polymer dissolved in a volatile solvent and a pressurized gas that flows around the polymer solution, generating fibers that are deposited in the direction of gas flow. This method is more favored compared to electrospinning due to the fact that it is less expensive and is easier to interface. This method has the ability to deposit conformal fibers onto both planar and non-planar substrates with a deposition rate that is relatively ten times faster than electrospinning.
Just like commercial airbrushes the nanofibrous airbrush technique can be used to “paint” nanofibers onto a more extensive range of targets and for the carrier solvent to evaporate quickly before the polymer fibers deposit on the collection surface. Although acute exposure to high concentrations of a solvent such as acetone may be toxic, studies have shown that SBS from acetone directly onto cells did not affect viability, resulting in preventing issue of biocompatibility.
Complication of the airbrush technique arises when formation of fiber mats with the local fiber bundles, this is induced by the morphological differences in fibers and crystalline structures.
Source: [ 12 ]
In 1999, researchers(Need to identify) pioneered a method creating nano-fibrous polyester based scaffolds with high porosity and sub-micron fibers dimensions through the method of phase separation.
Phase separation, also called as phase inversion, is a technique that has been employed to generate porous polymers scaffolds by promoting the separation of a polymeric solution into two phases: a polymer-rich phase and a polymer-poor phase.
Polymer solution is driven to separate in phases through cooling or non-solvent exchange, in a way that the polymer is not thermodynamically miscible anymore and forms polymer-rich domains within the solvent. Next, the solvent is extracted and the scaffold is frozen to maintain the structure. Lastly, lyophilization forms a fibrous scaffold with diameters between 50 and 500 nm(nanometers) and able to exhibit 98.5% porosity. Again this method of fabrication is used to create nano-fibrous scaffolds out of aliphatic polyesters.
Solvents that are used include THF( developing the best results), DMF, THF/methanol, THF/acetone, dioxane/methodal, dioxane/H2O, and dioxane/acetone).
Phase separation approximates more to conventional foams with larger pore sizes, implying that this method would be prone to cell infiltration, making it favorable for tissue engineering.. Phase separation can also lead to smaller pores being produced, however there is difficulty to control the diameter of fibrous due to the fact that the initial polymer concentration does not lead to larger fiber diameters in phase separated scaffolds.
This method of fabrication promotes cell growth, proliferation and differentiation, making it suitable to be used as tissues for artificial organs, neural networks, bioreactors, cell sources and drug delivery systems.
Source: [ 12 ]
“Spinneret based turntable engineered parameters” or STEP technique has been required for nanofiber networks with controllable fiber diameters, controllable spacing, and for the orientation of individual fibers. During this technique micro/nano fibers are pulled from the pendant solution droplet and allows for a collection of highly aligned fibers of uniform dimensions on the substrate. It promotes control of the dimensions of the fibers deposited in the aligned configurations, thus creating a platform for the investigation of cellular dynamics and cellular adhesion on scaffolds. The technique allows precise spacing and orientation of fibers into planar or non-planar structures using a wide spectrum of polymers. However, there is a difficulty in obtaining fibers smaller than 100 nm and as well as limitation to viscoelastic materials used in the STEP technique.
Nano-fibrous scaffolds, created from STEP techniques, have the ability to be used for a wide range of applications in tissue engineering
Source: [ 13 ]
By 2012 the US over half a million people receive bone defect repairs yearly with an estimated cost of $2.5 million and has doubled in recent years. In the US, bone is one of the most transplanted tissues and the increasing demand of bone grafts and substitutes was estimated to be 3.3 billion of revenue. Investments in research in tissue engineering solutions have had a massive market especially for bone.
As a scaffolding tissue, bone is responsible for support, protection, load bearing and hematopoietic functions. For small defects the human bone has the ability to continuously remodel and rebuild upon itself. However, large scale defects, inflammations caused by accidents, infections and tumors make it difficult for the bone to heal, requiring external interventions. The growing shortage of donors, rejection of transplants, and mechanical failure have made it difficult to have lasting solutions. Advancements in nanotechnology have enabled the applications for 3D printing in tissue engineering for the development of Bone scaffolds.
Bone scaffolds are typically made of porous biodegradable materials that provide the mechanical support during repair regeneration of damaged and diseased bone. The design of the scaffolds presents a surface that promotes cell attachments, growth, and differentiation, while providing a porous network for tissue growth. For bone scaffold continuous ingrowth of bone tissue, interconnected porosity is important as it can allow nutrients and molecules to transport to inner parts of scaffold to facilitate cell ingrowth, vascularization, as well as waste material removal.
The 3D bioprinting method has been used to fabricate more ideal structural scaffolds with better control of pore morphology, pore size and porosity. 3D printing can be essential to bone scaffolds as it takes into account the high degree of porosity together with high mechanical strength, which is critical for the bone scaffold to perform.
Cardiac muscle, on the other hand, has an elastic modulus of only around 10 MPa, 3 orders of magnitude smaller than bone. However, it experiences constant cyclic loading as the heart pumps. [ 14 ] This means that the scaffold must be both tough and elastic, a property achieved using polymeric materials.
Source: [ 15 ]
Spinal cord injury can be seriously detrimental to normal form and function in the human body, often leading to major loss of motor and sensory function that can even affect the whole of the body below the injury level. The number of global spinal cord injury cases rose to 27.04 million in 2016 where each patient can cost the economy from $1–5 million for a given case. As a result, there is a significant need for novel solutions to address the issue.
Novel biomaterial and tissue engineering strategies have been developed recently to address the need, mainly centering around formulating nanoscaffolds that fill the gap created in the injury site and that foster a pro-regenerative environment that help to facilitate restoration of the spinal cord structure and function. This is achieved through physically connecting the exposed areas in the spinal cord via scaffold as well as providing a favorable environment for regenerative cell types such as mesenchymal stem cells and Schwann cells and for promoting axon restoration and remyelination. Olfactory ensheathing cells, stem cells, and other neural progenitor cells play a large part in creating a stimulating environment for regenerative purposes.
In order to make these nanoscaffolds, both natural and synthetic polymers are used in their synthesis. For natural polymers, hyaluronic acid and collagen are two of the major candidates used in industry today. Hyaluronic acid is a major component of the extracellular matrix and has variable properties depending on its molecular weight, which is useful in compensating for properties necessary for a good scaffold. Collagen is also a major component of the extracellular matrix, most importantly in central nervous tissue where it has good histocompatibility and supports adhesion and growth. | https://en.wikipedia.org/wiki/Nano-scaffold |
Nano-suction is a technology that uses vacuum , negative fluid pressure and millions of nano-sized suction cups to securely adhere any object to a flat non-porous surface . When the nano-suction object is pressed against a flat surface, millions of miniature suction cups create a large vacuum, generating a strong suction force that can hold a tremendous amount of weight. The nature of the technology allows easy removal without residue, and makes it reusable.
There have been a wide range of applications of nano-suction technology, also known as "anti-gravity", ranging from hooks, frames, mirrors, notepad organisers, mobile phone [ 1 ] cases [ 2 ] [ 3 ] and large houseware products. | https://en.wikipedia.org/wiki/Nano-suction_technology |
The nano-tetherball sensor is one of newly discovered methods in detecting glucose in the human body. The nano-tetherball sensor for glucose has attracted attention of diabetic medical community due to its methods and high sensitivity in performance. The machine’s name comes from the fact that its design is similar to a small cube-shaped tetherball . Nano machines have been in the biosensor industry for more than two decades, and they have performed a number of different beneficial roles for diabetic patients. Despite the many opto/electronic mechanisms on the market, from a physical and chemical point of view, the nanomachine optical fiber provides many advantages over the other types. [ 1 ]
These advantages include its remote in-situ or actual detection; its wavelength has the highest degree of selectivity , with high information competence and analysis with multi-channels of wide capacity for detecting reagents that are non-responsive in electrical structures . The cubes rely on the tetherball structure and involve manipulation of tiny amounts of lasers in micro-channel using Nano-tetherballs. The Nano-tetherball process has the potential of being the most reliable in the accumulation of information. Medical statements that emphasize how the machine compares with other digital data storage and retrieval processes, to determine exactly how effective the machine is with processing the data detected and how to use said data. The information collected will be helpful for the formulation of treatments which are more practical than
other digital bio-optical machines provide. [ 2 ]
This fresh biosensor is more responsive than others in two very significant roles; glucose sensors need at least six times more glucose to produce an indicator, and the original sensor can gather an overindulgence of a wider variety of glucose application, meaning it can be used for number of functions. Much work has gone into developing the optimal electrode configuration to match biosensing needs. This structure is at times further functionalized to complete the biosensor fabrication process. A multi-wall platinum substrate , subsequently functionalized by oxidation , helps to allow the effectivity on the control of the glucose oxidase enzymes . The open ends of nanotubes , which are carboxylated (CNT), are used for the control of the enzymes and signaling detection monitor by the platinum substrate which gives the actual transduction platform . This glucose oxidase functionalized MWNT biosensor was used to detect various amounts of glucose. In devices such as these the CNTs play a dual role a substrate to attach biologically significant molecules and as the transducer component of the biosensor. | https://en.wikipedia.org/wiki/Nano-tetherball_sensor |
Nano-thermite or super-thermite is a metastable intermolecular composite (MIC) characterized by a particle size of its main constituents, a metal fuel and oxidizer , under 100 nanometers . This allows for high and customizable reaction rates. Nano-thermites contain an oxidizer and a reducing agent , which are intimately mixed on the nanometer scale. MICs, including nano-thermitic materials, are a type of reactive materials investigated for military use, as well as for general applications involving propellants, explosives, and pyrotechnics .
What distinguishes MICs from traditional thermites is that the oxidizer and a reducing agent, normally iron oxide and aluminium , are in the form of extremely fine powders ( nanoparticles ). This dramatically increases the reactivity relative to micrometre -sized powder thermite. As the mass transport mechanisms that slow down the burning rates of traditional thermites are not so important at these scales, [ citation needed ] the reaction proceeds much more quickly.
Historically, pyrotechnic or explosive applications for traditional thermites have been limited due to their relatively slow energy release rates. Because nanothermites are created from reactant particles with proximities approaching the atomic scale, energy release rates are far greater. [ 1 ]
MICs or super-thermites are generally developed for military use, propellants , explosives, incendiary devices , and pyrotechnics . Research into military applications of nano-sized materials began in the early 1990s. [ 2 ] Because of their highly increased reaction rate, nano-thermitic materials are being studied by the U.S. military with the aim of developing new types of bombs several times more powerful than conventional explosives. [ 3 ] Nanoenergetic materials can store more energy than conventional energetic materials and can be used in innovative ways to tailor the release of this energy. Thermobaric weapons are one potential application of nanoenergetic materials. [ 4 ]
There are many possible thermodynamically stable fuel-oxidizer combinations. Some of them are:
In military research, aluminium- molybdenum oxide , aluminium- Teflon and aluminium-copper(II) oxide have received considerable attention. [ 2 ] Other compositions tested were based on nanosized RDX and with thermoplastic elastomers . PTFE or other fluoropolymer can be used as a binder for the composition. Its reaction with the aluminium, similar to magnesium/teflon/viton thermite, adds energy to the reaction. [ 5 ] Of the listed compositions, that with potassium permanganate has the highest pressurization rate . [ 6 ]
The most common method of preparing nanoenergetic materials is by ultrasonification in quantities of less than 2g. Some research has been developed to increase production scales. Due to the very high electrostatic discharge (ESD) sensitivity of these materials, sub 1 gram scales are currently typical.
Nanoaluminum, or ultra fine grain (UFG) aluminum, powders are a key component of most nano-thermitic materials. A method for producing this material is the dynamic gas-phase condensation method, pioneered by Wayne Danen and Steve Son at Los Alamos National Laboratory . A variant of the method is being used at the Indian Head Division of the Naval Surface Warfare Center . Another method for production is electrothermal synthesis, developed by NovaCentrix, which uses a pulsed plasma arc to vaporize the aluminum. The powders made by the dynamic gas-phase condensation and the electrothermal synthesis processes are indistinguishable. [ 7 ] A critical aspect of the production is the ability to produce particles of sizes in the tens of nano-meter range, as well as with a limited distribution of particle sizes. In 2002, the production of nano-sized aluminum particles required considerable effort, and commercial sources for the material were limited. [ 2 ]
An application of the sol-gel method, developed by Randall Simpson, Alexander Gash and others at the Lawrence Livermore National Laboratory , can be used to make the actual mixtures of nano-structured composite energetic materials. Depending on the process, MICs of different density can be produced. Highly porous and uniform products can be achieved by super-critical extraction. [ 2 ]
The most common types of production are in liquids or via resonant acoustic mixing. However, more complicated methods like the ones previously mentioned are used. [ 8 ]
As with all explosives, research into control yet simplicity has been a goal of research into nanoscale explosives. [ 2 ] Some can be ignited with laser pulses. [ 2 ]
MICs have been investigated as a possible replacement for lead (e.g. lead styphnate , lead azide ) in percussion caps and electric matches . Compositions based on Al-Bi 2 O 3 tend to be used. PETN may be optionally added. [ 9 ]
Aluminium powder can be added to nano explosives . Aluminium has a relatively low combustion rate and a high enthalpy of combustion . [ 10 ]
The products of a thermite reaction, resulting from ignition of the nano-thermitic mixture, are usually metal oxides and elemental metals. At the temperatures prevailing during the reaction, the products can be solid, liquid or gaseous, depending on the components of the mixture. [ 11 ]
Like conventional thermite, super thermite reacts at very high temperature and is difficult to extinguish. The reaction produces dangerous ultra-violet (UV) light, requiring that the reaction not be viewed directly or that special eye protection (for example, a welder's mask) be worn.
In addition, super thermites are very sensitive to electrostatic discharge (ESD). Surrounding the metal oxide particles with carbon nanofibers may make nanothermites safer to handle. [ 12 ] | https://en.wikipedia.org/wiki/Nano-thermite |
NanoLanguage is a scripting interface built on top of the interpreted programming language Python , and is primarily intended for simulation of physical and chemical properties of nanoscale systems.
Over the years, several electronic-structure codes based on density functional theory have been developed by different groups of academic researchers; VASP , Abinit , SIESTA , and Gaussian are just a few examples. The input to these programs is usually a simple text file written in a code-specific format with a set of code-specific keywords. [ 1 ] [ 2 ] [ 3 ]
NanoLanguage was introduced by Atomistix A/S as an interface to Atomistix ToolKit (version 2.1) in order to provide a more flexible input format. A NanoLanguage script (or input file) is just a Python program and can be anything from a few lines to a script performing complex numerical simulations, communicating with other scripts and files, and communicating with other software (e.g. plotting programs).
NanoLanguage is not a proprietary product of Atomistix and can be used as an interface to other density functional theory codes as well as to codes utilizing e.g. tight-binding , k.p, or quantum-chemical methods. [ 4 ] [ 5 ]
Built on top of Python , NanoLanguage includes the same functionality as Python and with the same syntax. Hence, NanoLanguage contains, among other features, common programming elements ( for loops , if statements , etc.), mathematical functions, and data arrays .
In addition, a number of concepts and objects relevant to quantum chemistry and physics are built into NanoLanguage, e.g. a periodic table , a unit system (including both SI units and atomic units like Ångström ), constructors of atomic geometries, and different functions for density-functional theory and transport calculations. [ 6 ]
This NanoLanguage script uses the Kohn–Sham method to calculate the total energy of a water molecule as a function of the bending angle. | https://en.wikipedia.org/wiki/NanoLanguage |
The NanoMemPro IPPC database focus the operations where membranes are introduced as Best Available Techniques in the industrial areas addressed by the IPPC Directive.
The Integrated Pollution Prevention and Control (IPPC) Directive was adopted by the European Council on September 24, 1996. It defines the obligations with which highly polluting industrial and agricultural activities must comply. [ 1 ]
It establishes a procedure for authorizing these activities: a permit is issued if certain environmental conditions are met.
The IPPC Directive aims to minimise pollution from various sources throughout the European Union (it concerns both new and existing installations). To do so, all industrial installations covered by the Annex I of the IPPC Directive (see [ 2 ] ) are required to obtain an authorisation (permit) from the authorities in the EU countries before they are allowed to operate. The permits granted must be based on the concept of Best Available Techniques (or BAT).
The IPPC Directive covers 33 industrial sectors where in almost all of them membrane processes appear as BAT, not only as an end-of-pipe solution for effluent treatment but mainly as a part of the industrial production processes.
Membrane process integration play a crucial role, depending on the industrial sector in which they are integrated, and these roles may be:
The IPPC Database was designed by the NanoMemPro Network of Excellence [ 3 ] to focus the operations where membranes are introduced as BAT in the industrial areas addressed by the IPPC Directive documents.
The Database built allows any user to search information upon the following criteria:
The information states which membrane processes are defined as a BAT in a given industrial sector and what is the application/purpose of that membrane process(es).
When accessing the Database, one can enter a username and password. This password insertion is used only by the database manager. To view and search the information of the database, just press the OK button, ignoring the password insertion procedure.
This IPPC Database is available in the NanoMemPro website. [ 4 ] | https://en.wikipedia.org/wiki/NanoMemPro_IPPC_Database |
NanoPutians are a series of organic molecules whose structural formulae resemble human forms. [ 1 ] James Tour 's research group designed and synthesized these compounds in 2003 as a part of a sequence on chemical education for young students. [ 2 ] The compounds consist of two benzene rings connected via a few carbon atoms as the body, four acetylene units each carrying an alkyl group at their ends which represents the hands and legs, and a 1,3-dioxolane ring as the head. Tour and his team at Rice University used the NanoPutians in their NanoKids educational outreach program. The goal of this program was to educate children in the sciences in an effective and enjoyable manner. They have made several videos featuring the NanoPutians as anthropomorphic animated characters.
Construction of the structures depends on Sonogashira coupling and other synthetic techniques. By replacing the 1,3-dioxolane group with an appropriate ring structure, various other types of putians have been synthesized, e.g. NanoAthlete, NanoPilgrim, and NanoGreenBeret. Placing thiol (R-SH) functional groups at the end of the legs enables them to "stand" on a gold surface.
"NanoPutian" is a portmanteau of nanometer , a unit of length commonly used to measure chemical compounds, and lilliputian , a fictional race of humans in the novel Gulliver's Travels by Jonathan Swift .
While there are no chemical or practical uses for the NanoKid molecule or any of its known derivatives outside of the classroom, James Tour has turned the NanoKid into a lifelike character to educate children in the sciences. The goals of the outreach program, as described on the NanoKids website, are:
To accomplish these goals, several video clips, CDs, as well as interactive computer programs were created. Tour and his team invested over $250,000 into their project. In order to raise the funds for this endeavor, Tour used unrestricted funds from his professorship and small grants from Rice University, the Welch Foundation , the nanotech firm Zyvex , and Texas A&M University . Tour also received $100,000 in 2002 from the Small Grants for Exploratory Research program, a division of the National Science Foundation . [ 4 ]
The main characters in the videos are animated versions of the NanoKid. They star in several videos and explain various scientific concepts, such as the periodic table , DNA , and covalent bonding .
Rice conducted several studies into the effectiveness of using the NanoKids materials. These studies found mostly positive results for the use of the NanoKids in the classroom. A 2004–2005 study in two schools districts in Ohio and Kentucky found that using NanoKids led to a 10–59% increase in understanding of the material presented. Additionally, it was found that 82% of students found that NanoKids made learning science more interesting. [ 5 ]
To create the first NanoPutian, dubbed the NanoKid, 1,4-dibromobenzene was iodinated in sulfuric acid . To this product, “arms”, or 3,3-Dimethylbutyne, were then added through Sonogashira coupling . Formylation of this structure was then achieved through using the organolithium reagent n-butyllithium followed by quenching with N,N-dimethylformamide (DMF) to create the aldehyde. 1,2-Ethanediol was added to this structure to protect the aldehyde using p-toluenesulfonic acid as a catalyst . Originally, Chanteau and Tour aimed to couple this structure with alkynes, but this resulted in very low yields of the desired products. To remedy this, the bromide was replaced with iodide through lithium-halogen exchange and quenching by using 1,2-diiodoethane . This created the final structure of the upper body for the NanoKid. [ 1 ]
The synthesis of NanoPutian’s lower body begins with nitroaniline as a starting material. Addition of Br 2 in acetic acid places two equivalents of bromine on the benzene ring. NH 2 is an electron donating group , and NO 2 is an electron withdrawing group , which both direct bromination to the meta position relative to the NO 2 substituent. Addition of NaNO 2 , H 2 SO 4 , and EtOH removes the NH 2 substituent. The Lewis acid SnCl 2 , a reducing agent in THF/EtOH solvent, replaces NO 2 with NH 2 , which is subsequently replaced by iodine upon the addition of NaNO 2 , H 2 SO 4 , and KI to yield 3,5-dibromoiodobenzene. In this step, the Sandmeyer reaction converts the primary amino group (NH 2 ) to a diazonium leaving group (N 2 ), which is subsequently replaced by iodine. Iodine serves as an excellent coupling partner for the attachment of the stomach, which is executed through Sonogashira coupling with trimethylsilylacetylene to yield 3,5-dibromo(trimethylsilylethynyl)benzene. Attachment of the legs replaces the Br substituents with 1-pentyne through another Sonogashira coupling to produce 3,5-(1′-Pentynyl)-1-(trimethylsilylethynyl) benzene. To complete the synthesis of the lower body, the TMS protecting group is removed by selective deprotection through the addition of K 2 CO 3 , MeOH, and CH 2 Cl 2 to yield 3,5-(1′-Pentynyl)-1-ethynylbenzene. [ 1 ]
To attach the upper body of the NanoKid to the lower body, the two components were added to a solution of bis(triphenylphosphine)palladium(II) dichloride , copper(I) iodide , TEA , and THF . This resulted in the final structure of the NanoKid. [ 1 ]
NanoProfessionals have alternate molecular structures for the top of the head, and possibly include a hat. Most can be synthesized from the NanoKid by an acetal exchange reaction with the desired 1,2- or 1,3- diol, using p -toluenesulfonic acid as catalyst and heated by microwave irradiation for a few minutes. The ultimate set of products was a recognizably diverse population of NanoPutians: NanoAthlete, NanoPilgrim, NanoGreenBeret, NanoJester, NanoMonarch, NanoTexan, NanoScholar, NanoBaker, and NanoChef. [ 2 ]
The majority of the figures are easily recognizable in their most stable conformation . A few have as their stable conformation a less recognizable shape, so these are often drawn in the more recognizable but less stable way. Many liberties were taken in the visual depiction of the head dressings of the NanoPutians. [ 2 ] Some products are formed as a mixture of diastereomers —the configuration of the "neck" compared to parts of the "hat". [ 1 ]
3-Butyn-1-ol was reacted with methanesulfonyl chloride and triethanolamine to produce its mesylate . The mesylate was displaced to make thiolacetate. The thiol was coupled with 3,5-dibromo(trimethylsilylethynyl)benzene to create a free alkyne. The resulting product, 3,5-(4’-thiolacetyl-1’-butynyl)-1-(trimethylsilylethynyl)-benzene, had its trimethylsilyl group removed using tetra-n-butylammonium fluoride (TBAF) and AcOH/Ac 2 O in THF. The free alkyne was then coupled with the upper body product from the earlier synthesis. This resulted in a NanoKid with protected thiol feet. [ 1 ]
To make the NanoKid “stand’, the acetyl protecting groups were removed through the use of ammonium hydroxide in THF to create the free thiols. A gold-plated substrate was then dipped into the solution and incubated for four days. Ellipsometry was used to determine the resulting thickness of the compound, and it was determined that the NanoKid was upright on the substrate. [ 1 ]
Synthesis of the upper part of the NanoPutian chain begins with 1,3-dibromo-2,4-diiodobenzene as the starting material. Sonogashira coupling with 4-oxytrimethylsilylbut-1-yne produces 2,5-bis(4-tert-butyldimethylsiloxy-1′-butynyl)-1,4-di-bromobenzene. One of the bromine substituents is converted to an aldehyde through an S N 2 reaction with the strong base, n-BuLi, and THF in the aprotic polar solvent, DMF to produce 2,5-bis(4-tert-butyldimethylsiloxy-1′-butynyl)-4-bromobenzaldehyde. Another Sonogashira coupling with 3,5-(1′-Pentynyl)-1-ethynylbenzene attaches the lower body of the NanoPutian. The conversion of the aldehyde group to a diether “head” occurs in two steps. The first step involves addition of ethylene glycol and trimethylsilyl chloride (TMSCl) in CH 2 Cl 2 solvent. Addition of TBAF in THF solvent removes the silyl protecting group. [ 1 ] | https://en.wikipedia.org/wiki/NanoPutian |
Nano is an international peer-reviewed scientific journal published by World Scientific , covering recent developments and discussions in the field of nanoscience and technology. Topics covered include nanomaterials , characterization tools, fabrication methods, numerical simulation, and theory.
Established in 2006, the journal started as bimonthly, switched to 8 issues per year in 2014, and to monthly in 2016. According to the Journal Citation Reports , the journal had a 2023 impact factor of 1.0. [ 1 ]
The journal is abstracted and indexed in the Science Citation Index Expanded , ISI Alerting Services, Materials Science Citation Index , Current Contents /Physical, Chemical & Earth Sciences, and Inspec .
This article about a nanotechnology journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Nano_(journal) |
Nano Energy is a monthly peer-reviewed scientific journal covering nanotechnology and energy . It was established in 2012 and is published by Elsevier . Current editor-in-chiefs are Zhiqun Lin ( National University of Singapore ) & Weiguo Hu ( University of the Chinese Academy of Sciences ).
The journal is abstracted and indexed in:
According to the Journal Citation Reports , the journal has a 2023 impact factor of 16.8. [ 7 ] | https://en.wikipedia.org/wiki/Nano_Energy |
NanoDSF is a type of differential scanning fluorimetry (DSF) method used to determine conformational protein stability by employing intrinsic tryptophan or tyrosine fluorescence , as opposed to the use of extrinsic fluorogenic dyes that are typically monitored via a qPCR instrument. [ 1 ] A nanoDSF assay is also known as a type of Thermal Shift Assay.
Protein stability is typically addressed by thermal or chemical unfolding experiments. [ 2 ] In thermal unfolding experiments, a linear temperature ramp is applied to unfold proteins, whereas chemical unfolding experiments use chemical denaturants in increasing concentrations. The thermal stability of a protein is typically described by the ' melting temperature ' or 'Tm', at which 50% of the protein population is unfolded, corresponding to the midpoint of the transition from folded to unfolded.
In contrast to conventional DSF methods, nanoDSF uses tryptophan or tyrosine fluorescence to monitor protein unfolding. Both the fluorescence intensity and the fluorescence maximum strongly depend on the close chemical environment of the tryptophan. [ 3 ] Typically, interior tryptophan residues in a more hydrophobic environment exhibit a notable emission red shift from approximately 330 nm to 350 nm upon protein unfolding and exposure to water. Quantification of these fluorescence wavelength shifts at various temperature intervals yields a measurement of T m . Accepted methods to detect and quantify the fluorescence wavelength shift include measuring the intensity at a single wavelength, computing a ratio of the intensity at two wavelengths (typically 330 nm and 350 nm), or calculating the barycentric mean (BCM) by measuring the center of mass of the fluorescence waveform. The latter BCM method takes advantage of the entire UV-fluorescence spectrum, thus allowing for flexibility when auto-fluorescent small molecules are present.
Applications of nanoDSF include protein or antibody engineering, membrane protein research, quality control and formulation development, and ligand binding. [ 4 ] [ 5 ] [ 6 ] [ 7 ] NanoDSF has also been utilized to rapidly evaluate the melting points of enzyme libraries for biotechnological applications. [ 8 ]
Currently there are at least four instruments on the market that can measure fluorescence wavelength shifts in a high-throughput manner while heating the samples through a defined temperature ramp. These instruments employ either proprietary quartz capillaries, cartridges, or plates [ 9 ] [ 10 ] [ 11 ] or generic high-throughput 384-well plastic plates [ 12 ] for sample analysis.
The nanoDSF technology was used to confirm on-target binding of BI-3231 to HSD17B13 and to elucidate its uncompetitive mode of inhibition with regards to NAD + . [ 13 ]
NanoDSF was used to compare the thermal stability of a matched set of anti-CD20 antibodies representing a range of variants. The results revealed a spectrum of activities. [ 14 ] | https://en.wikipedia.org/wiki/Nano_differential_scanning_fluorimetry |
In a general meaning a Nano flake is a flake (that is, an uneven piece of material with one dimension substantially smaller than the other two) with at least one nanometric dimension (that is, between 1 and 100 nm). A flake is not necessarily perfectly flat but it is characterized by a plate-like form or structure. There are nanoflakes of all sorts of materials.
In a more restricted meaning, in the context of solar energy, Nano flakes are a type of semiconductor that has potential for solar energy creation as the product itself is only in the prototype phase. With its crystalline structure the crystals are able to absorb light and harvest 30 percent of solar energy directed at its surface.
Nano flakes have a structure that contains tiny crystals in which millions of these crystals could fit into a single square centimeter. The tiny crystals absorb the sunlight and use the solar energy to convert it to electricity. This perfect crystalline structure is why this product can revolutionize solar energy. [ 1 ] The large surface to volume ratio and the texture of the surface of this nano structure provides a larger absorption rate of the sun's light energy. Work is ongoing to combine it with different semiconducting materials since the usual requirements of a need for a similar crystal structure for the carrier substrate is less stressed in the Nano flakes structure. The carrier substrate in the nano flakes purpose is to permit growth of the nano structures and works as a contact for the Nano structures when they are actively absorbing the sun's energy. [ 2 ]
Solar energy obtained from the Nano flakes can help benefit in a couple of ways. Nano flakes can potentially help lower the cost of solar energy. Also since more solar energy can theoretically be obtained from Nano flakes, their use can potentially keep the earth's environment cleaner by reducing the need for fossil fuels .
The high cost of solar energy stems from the difficulty of converting the solar energy into electricity for use, and less than 1 percent of the world's electricity comes from the sun because of this process. [ 3 ] Nano flakes can potentially help with the economic issues of solar energy by lowering the cost due to an easier process and a better outcome of energy. Nano flake technology can potentially make it easier to convert solar energy into electricity estimated at twice the amount that today's solar cells can harvest. This new technology can also potentially lower the cost of solar energy because it allows for a reduction in expensive semiconducting silicon . [ 1 ] Energy loss is also potentially reduced with a shorter distance of the solar energy transportation across smaller Nano flakes. [ 4 ]
Nano flake technology can also help keep the environment cleaner as the sun as the source it produces clean pure sustainable energy that can be converted into electricity. [ 3 ] While fossil fuel is the primary energy source for electricity, using solar energy obtained from Nano flakes will lower dependence on fossil fuels. When fossil fuels are burned for use they release a toxic gas which has a huge impact on earth's pollution. [ 4 ] Also the process of obtaining these fossil fuels is not good for the environment, whether it be mining for coal, drilling for oil, or hydraulic fracturing of the earth's surface to reach the oil and gas. [ 5 ] | https://en.wikipedia.org/wiki/Nano_flake |
The nano guitar is a microscopically small carved guitar. It was developed by Dustin W. Carr in 1997, under the direction of Professor Harold G. Craighead , in the Cornell Nanofabrication Facility. The idea came about as a fun way to illustrate nanotechnology , and captured popular attention. [ 1 ] It is disputed as to whether the nano guitar should be classified as a guitar , but it is the common opinion that it is in fact a guitar. [ 2 ]
Nanotechnology miniaturizes normal objects, in this case, a guitar. It can be used to create tiny cameras , scales , and covert listening devices . An example of this is smartdust , which can be either a camera or a listening device smaller than a grain of sand. [ 3 ] A nanometer is one-billionth of a meter. For comparison, a human hair is about 200,000 nanometers thick. The nano guitar is about as long as one-twentieth of the diameter of a human hair, 10 micrometers or 10,000 nanometers long. Each of the six ' strings ' is 50 nanometers wide. The entire guitar is the size of an average red blood cell . The guitar is carved from a grain of crystalline silicon by scanning a laser over a film called a ' resist '. This technique is known as electron-beam lithography .
The guitar strings can be made to vibrate by tiny lasers using an atomic force microscope , in the same way, a guitar player might use a plectrum . The strings vibrate at around 40 000 000 Hz , roughly 15 octaves higher than a normal guitar , which can typically reach up to 1318.510 Hz. Even if its sound were amplified, it could not be detected by the human ear . [ 4 ]
The nano guitar illustrates inaudible technology that is not meant for musical entertainment. The application of frequencies generated by nano-objects is called sonification . Such objects can represent numerical data and provide support for information processing activities of many different kinds that produce synthetic non-verbal sounds. [ 5 ] Since the manufacture of the nano-guitar, researchers in the lab headed by Dr. Craighead have built even tinier devices. One thought is that they may be useful as tiny scales to measure tinier particles, such as bacteria , which may aid in diagnosis . [ 6 ] | https://en.wikipedia.org/wiki/Nano_guitar |
Nano neuro knitting is an emerging technology for repairing nervous system tissues via nano scaffolding techniques . [ 1 ] Currently being explored in numerous research endeavors, nano neuro knitting has been shown to allow partial reinnervation in damaged areas of the nervous system through the interactions between potentially regenerative axons and peptide scaffolds. [ 1 ] This interaction has been shown to lead to sufficient axon density renewal to the point that functionality is restored. While nano neuro knitting shows promise, the uncertainty of the effects in human subjects warrants further investigation before clinical trials initiate. [ 1 ]
The process of nano neuro knitting for nervous system tissue repair is carried out by engineering nanostructures for use as neural prosthetics and scaffolding in the brain. [ 2 ] The nano neuro knitting process is two-fold. Firstly, the nanostructure is constructed. This entails creating electrospun nanofibers that are combined with self-assembling peptides , molecules made up of amino acids that spontaneously form into nanostructures. [ 2 ] Electrospun nanofibers are commonly used in tissue grafts as they resemble natural tissue and are easy to fabricate. [ 3 ] Peptide-based nanomaterials are used due to their highly permissive nature which creates an easily attachable landscape for nerve-cells. [ 4 ] Scaffolds using a silk fibroin peptide (SF16) have also shown promise in nerve repair due to silk's biologically compatibility composition and mechanical features. [ 5 ] Secondly, these nanostructures are transplanted into the area where tissue damage has occurred. [ 2 ] Repairing damaged tissue in the nervous system using engineered nanofibers is a way of knitting damaged tissue back together. [ 4 ] The main goal is to create a supplemental structure that imitates the body's natural connective tissue. This synthetic extracellular matrix works to fill in the gaps between damaged tissue sites, promoting axon regrowth and the return of normal neurological function. [ 2 ] [ 6 ]
Scaffolds produced using nanotechnology have enabled researchers to investigate clinically relevant applications that involve the promotion of tissue regeneration at sites of acute damage. In nano neuro knitting, these methods are applied specifically to the repair of tissues of the nervous system. [ 7 ]
Nano neuro knitting has been researched for ophthalmic applications. The Massachusetts Institute of Technology (MIT) has tested a self-assembling peptide nanofiber scaffold (SAPNS) on hamsters to repair optic tract damage. Following injection, axon regeneration repaired the hamsters’ transected superior colliculi and restored vision in the tested animals. [ 8 ]
The mechanism behind the regeneration observed in these hamster models has been proposed to involve local axons with the potential to regenerate, the surrounding extracellular matrix (ECM) , and the peptides of the nano scaffold. [ 1 ] It has been shown that nano scaffolds can be carefully constructed to promote axonal growth and prevent scar formation at lesion sites . [ 1 ] Using alternating positive and negative L- amino acids to form β-sheet ionic self-complementary peptides, nanofibers of the SAPNSs mimic the environment of the ECM and have been shown to serve as effective scaffolds in both in vitro and in vivo studies—appearing to be immunologically inert, feasibly excreted , and nontoxic to biological systems . [ 1 ] Whereas previous research has attempted to graft nerve tissue to the optic tract and resulted in complications (leg disabilities in the case of sciatic nerve grafts, for instance), nano neuro knitting has been shown to promote the regeneration of these tissues without such drawbacks. [ 1 ] While more research is required in order to understand how this technology works, scientists propose that SAPNSs either facilitate this neuroregeneration by promoting cell migration into the lesion area or bringing the lesion areas in closer proximity via contraction. [ 1 ]
One obstacle for drug delivery to the brain is the blood-brain barrier (BBB) . The small size of nanomaterials , however, allows nanotechnologies to pass through. The scaffolds that enable nano neuro knitting, hence, are able to bypass this boundary without affecting the BBB that serves the essential role of managing what can and cannot enter and leave the central nervous system (CNS) . [ 9 ] While nano neuro knitting and other nanotechnologies may eventually replace procedures currently used to repair damage to the CNS through their improved biodistribution and pharmacokinetics , the toxicity and long-term impacts of nanomaterial exposure in humans has yet to be sufficiently assessed. [ 9 ] While some studies demonstrate no immediate toxicity and immune responses , it has yet to be determined if this holds true for the human CNS (with particular concern for the retention of these materials in the brain and their capacity to form neurotoxic plaques ) and the rest of the body's systems over time. Fortunately, SAPNSs may breakdown naturally by peptidase activity. [ 9 ]
In addition, promising monitoring methods are being explored in order to monitor axon regeneration in vivo that would provide patients real-time feedback via manganese -enhanced magnetic resonance imaging (MEMRI). In this way, these potential therapies could be monitored efficiently. [ 10 ]
Spinal cord injuries (SCIs) cause damage to the nervous system, which can result in neurological disfunction. [ 11 ] The main barrier to recovery from a SCI arises from the absence of tissue regeneration ability, specifically in damage to a portion of the nerve cell called the axon . [ 12 ] [ 2 ] Damage to the spinal cord can result in irreversible deficiencies including paralysis and loss of sensation. [ 11 ]
As in ophthalmic applications, research has demonstrated that nano scaffolds may be an effective tool for repairing spinal cord injuries (SCIs) . Such studies have utilized rat models to show that electrospun nanofibers and SAPNSs can effectively serve as guidance channels for regeneration of neural tissue lost at sites of SCI. [ 2 ] Using these scaffolds with integrated, slowly-released proregenerative cytokines showed that SCI rat models could repair contused spinal cord tissue. After six months, the spinal cord cysts were shown to be replaced by bundles of myelinated axons, ECM, and vascularization . In addition, the rat models have been shown to regain motor control after this treatment. [ 2 ]
Studies also suggest that culturing Schwann cells (SCs) and neural progenitor cells (NPCs) in SAPNSs prior to transplantation can significantly improve SCI repair by promoting axon and blood vessel development in the scaffold which has been shown to connect damaged tissue back together. [ 12 ] | https://en.wikipedia.org/wiki/Nano_neuro_knitting |
Nano spray dryers refer to using spray drying to create particles in the nanometer range. Spray drying is a gentle method for producing powders with a defined particle size out of solutions, dispersions, and emulsions which is widely used for pharmaceuticals, food, biotechnology, and other industrial materials synthesis. [ 1 ]
In the past, the limitations of spray drying were the particle size (minimum 2 micrometres ), the yield (maximum around 70%), and the sample volume (minimum 50 ml for devices in lab scale). Recently, minimum particle sizes have been reduced to 300 nm , yields up to 90% are possible, and the sample amount can be as small as 1 ml. These expanded limits are possible due to new technological developments to the spray head, the heating system, and the electrostatic particle collector. [ 2 ] To emphasize the small particle sizes possible with this new technology, it has been described as "nano" spray drying. However, the smallest particles produced are in the sub-micrometre range common to fine particles rather than the nanometer scale of ultrafine particles .
The functional principle is basically the same as with normal spray dryers. There are just different technologies that are used to do similar things.
The drying gas enters the system via the heater. A new kind of heater system allows for laminar air flow . The spray head sprays the fine droplets with a narrow size distribution into the drying chamber. The droplets dry and become solid particles. The solid particles are separated in the electrostatic particle collector. The [exhaust gas] is filtered and sent to a fume hood or the environment. The inlet temperature is controlled by a temperature sensor. and can be very dangerous also due to particulate matter
Pharmaceuticals :
This technique is widely used in the pharma market. Because of the small sample amounts and the high yields, it is ideal for spray drying expensive substances in basic research. The following list shows examples of what is possible: [ 3 ]
Materials science :
This new technique offers new prospects in materials science , specially in the nanomaterial field. Now it is possible to spray dry fine particles. The following list shows examples of what is possible:
Food :
Also in the field of food science this technology offers new possibilities. Especially in the currently vibrant field of functional food , the following list shows examples of what is possible:
The spray head is one of the three new technologies that make "nano" spray drying possible.
A piezoelectric system precisely vibrates a fine mesh . Vibration produces fine droplets with a narrow size distribution . [ 4 ]
In the field of "nano" spray drying a new heating system is used to provide the drying gas to produce the particles. The gas flow in the system is laminar and not turbulent as in common spray drying. The advantage of a laminar flow is that the particles fall straight down from the spray head and do not stick to the glass wall.
The laminar flow is produced by pressing the air through a porous metal foam .
To collect the very fine particles a new technology is used in the field of "nano" spray drying. The reason is that common cyclone technology depends on the particle mass; particles smaller than 2 μm can't be separated and instead exit the system along with the exhaust gas.
The electrostatic particle collector charges the dry particles' surface and deflects them with an electrical field. To produce the electrical field, a high voltage (16 kV) is applied to a round collector tube. The electrical field builds up between the inner wall of the collector tube and the tips of a grounded star electrode. To have a low level of energy in the system the current is very low.
After getting deflected the particles stay at the inner wall of the particle collector tube and are completely uncharged. This separation method works fine for all kinds of materials.
The efficiency of the electrostatic particle collector is very high: 99% of all particles that enter the system are collected. | https://en.wikipedia.org/wiki/Nano_spray_dryer |
Nano tape , also called gecko tape (or commercially as Insanity Tape or Alien Tape ) is a synthetic adhesive tape consisting of arrays of carbon nanotubes transferred onto a backing material of flexible polymer tape. These arrays are called synthetic setae and mimic the nanostructures found on the toes of a gecko ; this is an example of biomimicry . The adhesion is achieved not with chemical adhesives , but via van der Waals forces , which are weak electric forces generated between two atoms or molecules that are very close to each other. [ 1 ] [ 2 ]
Geckos show a remarkable ability to climb smooth vertical surfaces at high speeds, exhibiting both strong attachment and easy rapid removal, or shear adhesion, of their feet. [ 3 ]
On a gecko's foot, micrometer-sized elastic hairs called setae are split into nanometer-sized structures called spatulas . The shear adhesion is achieved by forming and breaking van der Waals forces between these microscopic structures and the substrate. [ 4 ]
Nano tapes mimic these structures with carbon nanotube bundles, which simulate setae and individual nanotubes, which simulate spatulas, to achieve macroscopic shear adhesion and to translate the weak van der Waals interactions into high shear forces. The shear adhesion allows the tape to be easily peeled off in the manner a gecko lifts its foot. Since the carbon nanotube arrays leave no residue on the substrate, the tape can be reused many times. [ 5 ]
Nano tape is one of the first developments of synthetic setae , which arose from a collaboration between the Manchester Centre for Mesoscience and Nanotechnology , and the Institute for Microelectronics Technology in Russia. Work started in 2001 and two years later results were published in Nature Materials . [ 6 ]
The group prepared flexible fibers of polyimide as the synthetic setae structures on the surface of a 5 μm thick film of the same material using electron beam lithography and dry etching in an oxygen plasma . The fibres were 2 μm long, with a diameter of around 500 nm and a periodicity of 1.6 μm, and covered an area of roughly 1 cm 2 (see figure on the left). Initially, the team used a silicon wafer as a substrate, but found that the tape's adhesive power increased by almost 1,000 times if they used a soft bonding substrate such as Scotch tape. This is because the flexible substrate yields a much higher ratio of the number of setae in contact with the surface over the total number of setae. [ citation needed ]
The result of this "gecko tape" was tested by attaching a sample to the hand of a 15 cm high plastic Spider-Man figure weighing 40 g, which enabled it to stick to a glass ceiling, as is shown in the figure. The tape, which had a contact area of around 0.5 square centimetres (50 mm 2 ) with the glass, was able to carry a load of more than 100 grams (3.5 oz). However, the adhesion coefficient was only 0.06, which is low compared with real geckos (8~16). [ citation needed ]
Commercial nano tape is usually sold as double-sided tape that is useful for hanging lightweight items, such as pictures and decorative items on smooth walls. Using superaligned carbon nanotubes, some nano tapes can stay sticky in extreme temperatures. [ 2 ] | https://en.wikipedia.org/wiki/Nano_tape |
Nanoarchitectures for lithium-ion batteries are attempts to employ nanotechnology to improve the design of lithium-ion batteries . Research in lithium-ion batteries focuses on improving energy density , power density , safety, durability and cost.
Increased energy density requires inserting/extracting more ions from the electrodes . Electrode capacities are compared through three different measures: capacity per unit of mass (known as " specific energy " or "gravimetric capacity"), capacity per unit volume ("volumetric capacity"), and area-normalized specific capacity ("areal capacity").
Separate efforts focus on improving power density (rate of charge/discharge). Power density is based upon mass and charge transport, electronic and ionic conductivity , and electron-transfer kinetics; easy transport through shorter distance and greater surface area improve the rates. [ 1 ]
Carbon anodes are traditionally used because of lithium's ability to intercalate without unacceptable volumetric expansion. The latter damages the battery and reduces the amount of lithium available for charging. Reduced intercalation limits capacity. Carbon based anodes have a gravimetric capacity of 372 mAh/g for LiC 6. [ 2 ]
The specific capacity of silicon is approximately ten times greater than carbon. The atomic radius of Si is 1.46 angstroms , while the atomic radius of Li is 2.05 angstroms. The formation of Li 3.75 Si causes significant volumetric expansion, progressively destroying the anode. [ 3 ] Reducing the anode architecture to the nanoscale offers advantages, including improved cycle life and reduced crack propagation and failure. Nanoscale particles are below the critical flaw size within a conductive binder film. [ 2 ] [ 4 ] Reducing transport lengths(the distance between the anode and cathode) reduces ohmic losses (resistance).
Nanostructuring increases the surface area to volume ratio, which improves both energy and power density due to an increase in the electrochemically active area and a reduction in transport lengths. However, the increase also increases side reactions between the electrode and the electrolyte, causing higher self-discharge, reduced charge/discharge cycles and lower calendar life. Some recent work focused on developing materials that are electrochemically active within the range where electrolyte decomposition or electrolyte/electrode reactions do not occur. [ 1 ]
A research concept has been proposed in which the major parts of lithium-ion batteries, that is, the anode, electrolyte, and cathode, are combined into one functional molecule. A layer of such functional molecules aligned by the Langmuir-Blodgett method is placed in between two current collectors. [ 5 ] The feasibility has not been confirmed yet.
A significant majority of battery designs are two–dimensional and rely on layered construction. [ 6 ] Recent research has taken the electrodes into three-dimensions. This allows for significant improvements in battery capacity; a significant increase in areal capacity occurs between a 2d thick film electrode and a 3d array electrode. [ 7 ]
Solid state batteries employ geometry most similar to traditional thin-film batteries. Three-dimensional thin-films use the third dimension to increase the electrochemically active area. Thin film two dimensional batteries are restricted to between 2-5 micrometres, limiting areal capacity to significantly less than that of three-dimensional geometries.
Dimensionality is increased by using a perforated substrate. One way to create perforations is through inductive coupled plasma etching on silicon. [ 8 ]
Another approached used highly anisotropic etching of a silicon substrate through electrochemical or reactive ion etching to create deep trenches. The requisite layers, an anode, separator, and cathode, for a battery were then added by low-pressure chemical vapor deposition . The battery consists of a thin active silicon layer separated from a thin cathodic layer by a solid-state electrolyte . The electrochemically active area consists of 50 nm nanoparticles, smaller than the critical size for crack propagation. [ 9 ]
Another architecture is a periodic grouping of anodic and cathodic poles. For this design power and energy density is maximized by minimizing electrode separation. An innate non-uniform current density occurs and lowers cell efficiencies, reduces stability and produces non-uniform heating within the cell. Relative to a two dimensional battery the length (L) over which transport must occur is decreased by two-thirds, which improves kinetics and reduces ohmic loses. Optimization of L can lead to significant improvement in areal capacity; an L on the size scale of 500 micrometres results in a 350% increase in capacity over a comparable two dimensional battery. However, ohmic losses increase with L, eventually offsetting the enhancement achieved through increasing L.
For this geometry, four main designs were proposed: rows of anodes and cathodes, alternating anodes and cathodes, hexagonally packed 1:2 anodes:cathodes, and alternating anodic and cathodic triangular poles where the nearest neighbors in the row are rotated 180 degrees.
The row design has a large, non-uniform current distribution. The alternating design exhibits better uniformity, given a high number of electrodes of opposite polarity . For systems with an anode or cathode that is sensitive to non-uniform current density, non-equal numbers of cathodes and anodes can be used; the 2:1 hexagonal design allows for a uniform current density at the anode but a non-uniform current distribution at the cathode. Performance can be increased through changing the shape of the poles. The triangular design improves cell capacity and power by sacrificing current uniformity. [ 6 ] A similar system uses interdigitated plates instead of poles. [ 6 ]
In 2013 researchers used additive manufacturing to create stacked, interdigitated electrodes. The battery was no larger than a grain of sand. The process placed anodes and cathodes closer to each other than before. The ink for the anode was nanoparticles of one lithium metal oxide compound, and the ink for the cathode from nanoparticles of another. The printer deposited the inks onto the teeth of two gold combs, forming an interlaced stack of anodes and cathodes. [ 10 ] [ 11 ]
The concentric cylinder design is similar to interdigitated poles. Instead of discrete anode and cathode poles, the anode or cathode is kept as a pole that is coated by electrolyte. The other electrode serves as the continuous phase in which the anode/cathode resides. The main advantage is that the amount of electrolyte is reduced, increasing energy density. This design maintains a short transport distance like the interdigitated system and thus has a similar benefit to charge and mass transport, while minimizing ohmic loses. [ 6 ]
A version of the concentric cylinder packed particles or close-packed polymer to create a three-dimensionally ordered macroporous (3DOM) carbon anode. This system is fabricated by using colloidal crystal templating, electrochemical thin-film growth, and soft sol–gel chemistry. 3DOM materials have a unique structure of nanometer thick walls that surround interconnected and closed-packed sub-micrometer voids. The 3DOM structure is coated with a thin polymer layer and then filled with second conducting phase. This method leads to a battery with short transport lengths, high ionic conductivity and reasonable electrical conductivity. It removes the need for additives that do not contribute to electrochemical performance. Performance can be improved by coating with tin oxide nanoparticles to enhance the initial capacity. [ 12 ] The coating infiltrates the network formed by the 3DOM structure to produce uniform thickness.
Nanowire and nanotubes have been integrated with various battery components. The reason for this interest is because of shortened transport lengths, resistance to degradation and storage. For carbon nanotubes (CNT), lithium-ions can be stored on the exterior surface, in the interstitial sites between the nanotubes and on the tube's interior. [ 13 ]
Nanowires have been incorporated into the anode/cathode matrix to provide a builtin conductive charge collector and enhancing capacity. The nanowires were incorporated through a solution-based method that allows the active material to be printed on a substrate. [ 14 ]
Another approach uses a CNT-cellulose composite. CNTs were grown on a silicon substrate by thermal-CVD and then embedded in cellulose . Finally a lithium electrode is added on top of the cellulose across from the CNTs. [ 15 ]
In 2007 Si nanowires were fabricated on a steel substrate by a vapor-liquid solid growth method. These nanowires exhibited close to the theoretical value for silicon and showed only minimal fading after a 20% drop between the first to second cycles. This performance is attributed to the facile strain relaxation that allows for accommodations of large strains, while maintaining good contact with the current collector and efficient 1D electron transport along the nanowire. [ 16 ]
Periodic structures lead to non-uniform current densities that lower efficiency and decrease stability. The aperiodic structure is typically made of either aerogels or somewhat more dense ambigels [ 17 ] that forms a porous aperiodic sponge. Aerogels and ambigels are formed from wet gels; aerogels are formed when wet gels are dried such that no capillary forces are established, while ambigels are wet gels dried under conditions that minimize capillary forces. [ 18 ] Aerogels and ambigels are unique in that 75-99% of the material is ‘open’ but interpenetrated by a solid that is on the order of 10 nm, resulting in pores on the order of 10 to 100 nm. The solid is covalently networked and resistant to agglomeration and sintering . Beyond aperiodicity, these structures are used because the porous structure allows for rapid diffusion throughout the material, and the porous structure provides a large reaction surface. Fabrication is through coating the ambigel with a polymer electrolyte and then filling the void space with RuO 2 colloids that act as an anode. [ 19 ]
Most designs were half-cell experiments; testing only the anode or cathode. As geometries become more complex, non-line-of-sight methods to in-fill the design with electrolyte materials supply the oppositely charged electrode is essential. These batteries can be coated with various materials to improve their performance and stability. However, chemical and physical heterogeneity leaves molecular-level control a significant challenge, especially since the electrochemistry for energy storage is not defect-tolerant. [ 19 ]
LbL approaches are used to coat 3d nanoarchitecture. Electrostatically binding a charged polymer to an oppositely charged surface coats the surface with polymer. Repeated steps of oppositely charged polymer build up a well-controlled thick layer. Polyelectrolyte films and ultrathin (less than 5 nm) of electroactive polymers have been deposited on planar substrates using this method. However, problems exist with the deposition of polymers within complex geometries, e.g. pores, on the size scale of 50-300 nm, resulting in defective coatings. One potential solution is to use self-limiting approaches. [ 19 ]
Another approach to coating is ALD which coats the substrate layer-by-layer with atomic precision. The precision is because reactions are confined to the surface containing an active chemical moiety that reacts with a precursor; this limits thickness to one monolayer. This self-limiting growth is essential for complete coatings since deposition does not inhibit the access by other polymeric units to non-coated sites. Thicker samples can be produced by cycling gases in a similar manner to alternating with oppositely charged polymers in LbL. In practice ALD may require a few cycles in order to achieve the desired coverage and can result in varied morphologies such as islands, isolated crystallites, or nanoparticles. Morphology can alter electrochemical behavior and therefore must be carefully controlled. [ 19 ]
ALD was also used to deposit iron oxide on 3DOM carbon to enhance reactivity between lithium and oxygen. The iron was then coatedwith palladium nanoparticles, which effectively reduced carbon's destructive reaction with oxygen and improved the discharge cycle. Wang said the findings show 3DOm carbon can meet new performance standards when it is stabilized. [ 20 ]
Electropolymerization supplies a thin polymer film, 10 to 100 nm. The electropolymerization of an insulating polymer results in self-limiting deposition as the active moiety is protected; the deposition can also be self-limiting if the polymer can block the solubilized monomer and prohibit continued growth. Through the control of electrochemical variables, polyaniline and polythiophene can be deposited in a controlled manner. Styrene , methyl methacrylate , phenols and other electrically insulating polymers have been deposited on the electrodes to act as a separator that allows ionic transport, but inhibits electrical transport to prevent shorts. Mesoporous manganese dioxide ambigels have been protected by 7-9 nm films of polymer such that dissolution of the manganese dioxide in aqueous acid was avoided. Uniform coatings require the architecture to be wetted by the monomer solution; this can be achieved through a solution that displays a similar surface energy to that of the porous solid. As the scale continuous to decrease and transport through the solid becomes more difficult, pre-equilibration is needed to ensure coating uniformity. [ 18 ] | https://en.wikipedia.org/wiki/Nanoarchitectures_for_lithium-ion_batteries |
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