text stringlengths 11 320k | source stringlengths 26 161 |
|---|---|
Sodium bis(2-methoxyethoxy)aluminium hydride ( SMEAH ; [ 1 ] trade names Red-Al , Synhydrid , Vitride ) is a hydride reductant with the formula NaAlH 2 (OCH 2 CH 2 OCH 3 ) 2 . The trade name Red-Al refers to its being a red ucing al uminium compound. It is used predominantly as a reducing agent in organic synthesis . The compound features a tetrahedral aluminium center attached to two hydride and two alkoxide groups, the latter derived from 2-methoxyethanol . Commercial solutions are colorless/pale yellow and viscous. At low temperatures (below -60°C), the solution solidifies to a glassy pulverizable substance with no sharp melting point.
SMEAH is a versatile hydride reducing agent. It readily converts epoxides , aldehydes , ketones , carboxylic acids , esters , acyl halides , and anhydrides to the corresponding alcohols . Nitrogen derivates such as amides , nitriles , imines , and most other organonitrogen compounds are reduced to the corresponding amines . Nitroarenes can be converted to azoxyarenes, azoarenes, or hydroazoarenes, depending on the reaction conditions. [ 1 ]
Some common functional group reductions using SMEAH can be found below:
As a reagent , SMEAH is comparable with lithium aluminium hydride (LAH, LiAlH 4 ).
It is a safer alternative to LAH and related hydrides. SMEAH exhibits similar reducing effects, but does not have the inconvenient pyrophoric nature, short shelf-life, or limited solubility of LAH. Upon contact with air and moisture, SMEAH reacts exothermically but does not ignite, and tolerates temperatures up to 200°C. Under dry conditions it has unlimited shelf life. It is soluble in aromatic solvents, whereas LAH is only soluble in ethers. For example, a solution greater than 70 wt.% concentration in toluene is commercially available. The reagent can be modified to effect partial reductions. [ 1 ]
SMEAH in toluene under reflux has been used to reduce aliphatic p- toluenesulfonamides (TsNR 2 ) to the corresponding free amines and is one of the few reagents that can carry out this challenging reduction in general settings. Notably, LiAlH 4 does not reduce this functional group unless forcing conditions are used. [ 2 ] | https://en.wikipedia.org/wiki/Sodium_bis(2-methoxyethoxy)aluminium_hydride |
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/Sodium_bisulfite |
Sodium borohydride , also known as sodium tetrahydridoborate and sodium tetrahydroborate , [ 5 ] is an inorganic compound with the formula Na B H 4 (sometimes written as Na[BH 4 ] ). It is a white crystalline solid, usually encountered as an aqueous basic solution . Sodium borohydride is a reducing agent that finds application in papermaking and dye industries. It is also used as a reagent in organic synthesis. [ 6 ]
The compound was discovered in the 1940s by H. I. Schlesinger , who led a team seeking volatile uranium compounds. [ 7 ] [ 8 ] Results of this wartime research were declassified and published in 1953.
The compound is soluble in alcohols , certain ethers , and water, although it slowly hydrolyzes. [ 9 ]
Sodium borohydride is an odorless white to gray-white microcrystalline powder that often forms lumps. It can be purified by recrystallization from warm (50 °C) diglyme . [ 10 ] Sodium borohydride is soluble in protic solvents such as water and lower alcohols. It also reacts with these protic solvents to produce H 2 ; however, these reactions are fairly slow. Complete decomposition of a methanol solution requires nearly 90 min at 20 °C. [ 11 ] It decomposes in neutral or acidic aqueous solutions, but is stable at pH 14. [ 9 ]
NaBH 4 is a salt, consisting of the tetrahedral [BH 4 ] − anion. The solid is known to exist as three polymorphs : α , β and γ . The stable phase at room temperature and pressure is α - NaBH 4 , which is cubic and adopts an NaCl -type structure, in the Fm 3 m space group . At a pressure of 6.3 GPa, the structure changes to the tetragonal β - NaBH 4 (space group P42 1 c ) and at 8.9 GPa, the orthorhombic γ - NaBH 4 (space group Pnma ) becomes the most stable. [ 12 ] [ 13 ] [ 14 ]
For commercial NaBH 4 production, the Brown-Schlesinger process and the Bayer process are the most popular methods. In the Brown-Schlesinger process, sodium borohydride is industrially prepared from sodium hydride (produced by reacting Na and H 2 ) and trimethyl borate at 250–270 °C:
Millions of kilograms are produced annually, far exceeding the production levels of any other hydride reducing agent. [ 15 ] In the Bayer process, it is produced from inorganic borates, including borosilicate glass [ 16 ] and borax ( Na 2 B 4 O 7 ):
Magnesium is a less expensive reductant, and could in principle be used instead: [ 17 ] [ 18 ]
and
NaBH 4 reduces many organic carbonyls , depending on the conditions. Most typically, it is used in the laboratory for converting ketones and aldehydes to alcohols. [ 6 ] These reductions proceed in two stages, formation of the alkoxide followed by hydrolysis:
It also efficiently reduces acyl chlorides , anhydrides , α-hydroxy lactones , thioesters , and imines at room temperature or below. It reduces esters slowly and inefficiently with excess reagent and/or elevated temperatures, while carboxylic acids and amides are not reduced at all. [ 19 ]
Nevertheless, an alcohol, often methanol or ethanol, is generally the solvent of choice for sodium borohydride reductions of ketones and aldehydes. The mechanism of ketone and aldehyde reduction has been scrutinized by kinetic studies, and contrary to popular depictions in textbooks, the mechanism does not involve a 4-membered transition state like alkene hydroboration, [ 20 ] or a six-membered transition state involving a molecule of the alcohol solvent. [ 21 ] Hydrogen-bonding activation is required, as no reduction occurs in an aprotic solvent like diglyme . However, the rate order in alcohol is 1.5, while carbonyl compound and borohydride are both first order, suggesting a mechanism more complex than one involving a six-membered transition state that includes only a single alcohol molecule. It was suggested that the simultaneous activation of the carbonyl compound and borohydride occurs, via interaction with the alcohol and alkoxide ion, respectively, and that the reaction proceeds through an open transition state. [ 22 ] [ 23 ]
α,β-Unsaturated ketones tend to be reduced by NaBH 4 in a 1,4-sense, although mixtures are often formed. Addition of cerium chloride improves the selectivity for 1,2-reduction of unsaturated ketones ( Luche reduction ). α,β-Unsaturated esters also undergo 1,4-reduction in the presence of NaBH 4 . [ 9 ]
The NaBH 4 -MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols. [ 24 ] Mixing water or an alcohol with the borohydride converts some of it into unstable hydride ester, which is more efficient at reduction, but the reductant eventually decomposes spontaneously to produce hydrogen gas and borates. The same reaction can also occur intramolecularly: an α-ketoester converts into a diol, since the alcohol produced attacks the borohydride to produce an ester of the borohydride, which then reduces the neighboring ester. [ 25 ]
The reactivity of NaBH 4 can be enhanced or augmented by a variety of compounds. [ 26 ] [ 27 ]
Many additives for modifying the reactivity of sodium borohydride have been developed as indicated by the following incomplete listing.
Oxidation with iodine in tetrahydrofuran gives borane–tetrahydrofuran , which can reduce carboxylic acids to alcohols. [ 29 ]
Partial oxidation of borohydride with iodine gives octahydrotriborate : [ 30 ]
[BH 4 ] − is a ligand for metal ions. Such borohydride complexes are often prepared by the action of NaBH 4 (or the LiBH 4 ) on the corresponding metal halide. One example is the titanocene derivative: [ 31 ]
NaBH 4 reacts with water and alcohols, with evolution of hydrogen gas and formation of the corresponding borate, the reaction being especially fast at low pH. Exploiting this reactivity, sodium borohydride has been studied as a prototypes of the direct borohydride fuel cell .
The dominant application of sodium borohydride is the production of sodium dithionite from sulfur dioxide: Sodium dithionite is used as a bleaching agent for wood pulp and in the dyeing industry.
It has been tested as pretreatment for pulping of wood, but is too costly to be commercialized. [ 15 ] [ 32 ]
Sodium borohydride reduces aldehydes and ketones to give the related alcohols . This reaction is used in the production of various antibiotics including chloramphenicol , dihydrostreptomycin , and thiophenicol . Various steroids and vitamin A are prepared using sodium borohydride in at least one step. [ 15 ]
Sodium borohydride has been considered as a way to store hydrogen for hydrogen-fueled vehicles, as it is safer (being stable in dry air) and more efficient on a weight basis than most other alternatives. [ 33 ] [ 34 ] The hydrogen can be released by simple hydrolysis of the borohydride. However, such a usage would need a cheap, relatively simple, and energy-efficient process to recycle the hydrolysis product, sodium metaborate , back to the borohydride. No such process was available as of 2007. [ 35 ]
Although practical temperatures and pressures for hydrogen storage have not been achieved, in 2012 a core–shell nanostructure of sodium borohydride was used to store, release and reabsorb hydrogen under moderate conditions. [ 36 ]
Skilled professional conservator/restorers have used sodium borohydride to minimize or reverse foxing in old books and documents. [ 37 ]
A common laboratory demonstration "uncooks" eggs with sodium borohydride, as hydride reagents reduce disulfides to thiols . [ 38 ] To uncook an egg, breaking the hydrogen and hydrophobic bonds is not enough. [ 39 ] As sodium borohydride is toxic, the egg white uncooked after three hours is not edible, [ 39 ] but Vitamin C can be used instead. [ 40 ] [ 39 ]
Many derivatives and analogues of sodium borohydride exhibit modified reactivity of value in organic synthesis. [ 41 ] | https://en.wikipedia.org/wiki/Sodium_borohydride |
Sodium bromate , the inorganic compound with the chemical formula of NaBrO 3 , is the sodium salt of bromic acid . It is a strong oxidant .
Sodium bromate is mainly used in continuous or batch dyeing processes involving sulfur or vat dyes and as a hair-permagent , chemical agent, or gold solvent in gold mines when used with sodium bromide.
Sodium bromate can be produced from a solution of sodium carbonate and bromine using chlorine gas as the oxidising agent . [ 1 ]
It may also be produced by the electrolytic oxidation of aqueous sodium bromide . [ 2 ]
Bromate in drinking water is undesirable because it is a suspected human carcinogen . [ 3 ] [ 4 ] Its presence in Coca-Cola's Dasani bottled water forced a recall of that product in the UK . [ 5 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sodium_bromate |
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/Sodium_chlorate |
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/Sodium_chloride |
This page provides supplementary chemical data on sodium chloride .
The handling of this chemical may incur notable safety precautions. It is highly recommended that you seek the material safety data sheet ( MSDS ) for this chemical from a reliable source such as eChemPortal , and follow its direction.
Note: ρ is density, n is refractive index at 589 nm, [ clarification needed ] and η is viscosity, all at 20 °C; T eq is the equilibrium temperature between two phases: ice/liquid solution for T eq < 0–0.1 °C and NaCl/liquid solution for T eq above 0.1 °C. | https://en.wikipedia.org/wiki/Sodium_chloride_(data_page) |
Sodium chromate is the inorganic compound with the formula Na 2 CrO 4 . It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and deca hydrates . It is an intermediate in the extraction of chromium from its ores.
It is obtained on a vast scale by roasting chromium ores in air in the presence of sodium carbonate:
This process converts the chromium into a water-extractable form, leaving behind iron oxides. Typically calcium carbonate is included in the mixture to improve oxygen access and to keep silicon and aluminium impurities in an insoluble form. The process temperature is typically around 1100 °C. [ 1 ] For lab and small scale preparations a mixture of chromite ore, sodium hydroxide and sodium nitrate reacting at lower temperatures may be used (even 350 C in the corresponding potassium chromate system). [ 2 ] Subsequent to its formation, the chromate salt is converted to sodium dichromate , the precursor to most chromium compounds and materials. [ 3 ] The industrial route to chromium(III) oxide involves reduction of sodium chromate with sulfur .
It converts to sodium dichromate when treated with acids:
Further acidification affords chromium trioxide :
Aside from its central role in the production of chromium from its ores, sodium chromate is used as a corrosion inhibitor in the petroleum industry. [ 3 ] It is also a dyeing auxiliary in the textile industry. [ 3 ] It is a diagnostic pharmaceutical in determining red blood cell volume. [ 4 ]
In organic chemistry, sodium chromate is used as an oxidant, converting primary alcohols to carboxylic acids and secondary alcohols to ketones . [ 5 ] Sodium chromate is a strong oxidizer.
As with other Cr(VI) compounds, sodium chromate is carcinogenic . [ 6 ] The compound is also corrosive and exposure may produce severe eye damage or blindness. [ 7 ] Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children. | https://en.wikipedia.org/wiki/Sodium_chromate |
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/Sodium_cyanoborohydride |
Sodium dichromate is the inorganic compound with the formula Na 2 Cr 2 O 7 . However, the salt is usually handled as its dihydrate Na 2 Cr 2 O 7 ·2 H 2 O . Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. [ 1 ] In terms of reactivity and appearance, sodium dichromate and potassium dichromate are very similar. The sodium salt is, however, around twenty times more soluble in water than the potassium salt (49 g/L at 0 °C) and its equivalent weight is also lower, which is often desirable. [ 2 ]
Sodium dichromate is generated on a large scale from ores containing chromium(III) oxides. The ore is fused with a base, typically sodium carbonate , at around 1000 °C in the presence of air (source of oxygen):
This step solubilizes the chromium and allows it to be extracted into hot water. At this stage, other components of the ore such as aluminium and iron compounds, are poorly soluble. Acidification of the resulting aqueous extract with sulfuric acid or carbon dioxide affords the dichromate:
The dichromate is isolated as the dihydrate by crystallization. In this way, many millions of kilograms of sodium dichromate are produced annually. [ 1 ]
Since chromium(VI) is toxic, especially as the dust, such factories are subject to stringent regulations. For example, effluent from such refineries is treated with reducing agents to return any chromium(VI) to chromium(III), which is less threatening to the environment. [ 1 ] A variety of hydrates of this salt are known, ranging from the decahydrate below 19.5 °C (CAS# 13517-17-4 ) as well as hexa-, tetra-, and dihydrates. Above 62 °C, these salts lose water spontaneously to give the anhydrous material.
It is crystallised around 30 to 35 degrees C
Dichromate and chromate salts are oxidizing agents. For the tanning of leather, sodium dichromate is first reduced with sulfur dioxide .
In the area of organic synthesis , [ 2 ] this compound oxidizes benzylic and allylic C-H bonds to carbonyl derivatives. For example, 2,4,6-trinitrotoluene is oxidized to the corresponding carboxylic acid. [ 3 ] Similarly, 2,3-dimethylnaphthalene is oxidized by Na 2 Cr 2 O 7 to 2,3-naphthalenedicarboxylic acid. [ 4 ]
Secondary alcohols are oxidized to the corresponding ketone, e.g. menthol to menthone ; [ 5 ] dihydrocholesterol to cholestanone: [ 6 ]
Relative to the potassium salt, the main advantage of sodium dichromate is its greater solubility in water and polar solvents like acetic acid.
For hexavalent chrome plating , chromate is converted to the so-called chromic acid (essentially chromium trioxide ) by sulfuric acid.
Sodium dichromate can be used in fluorene to fluorenone conversion.
Like all hexavalent chromium compounds, sodium dichromate is carcinogenic . [ 7 ] The compound is also corrosive and exposure may produce severe eye damage or blindness. [ 8 ] Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children. | https://en.wikipedia.org/wiki/Sodium_dichromate |
Sodium dithionite (also known as sodium hydrosulfite ) is a white crystalline powder with a sulfurous odor. Although it is stable in dry air, it decomposes in hot water and in acid solutions .
The structure has been examined by Raman spectroscopy and X-ray crystallography . The dithionite dianion has C 2 symmetry , with almost eclipsed with a 16° O-S-S-O torsional angle. In the dihydrated form ( Na 2 S 2 O 4 ·2H 2 O ), the dithionite anion has gauche 56° O-S-S-O torsional angle. [ 1 ]
A weak S-S bond is indicated by the S-S distance of 239 pm, which is elongated by ca. 30 pm relative to a typical S-S bond. [ 2 ] Because this bond is fragile, the dithionite anion dissociates in solution into the [SO 2 ] − radicals, as has been confirmed by EPR spectroscopy . It is also observed that 35 S undergoes rapid exchange between S 2 O 4 2− and SO 2 in neutral or acidic solution, consistent with the weak S-S bond in the anion. [ 3 ]
Sodium dithionite is produced industrially by reduction of sulfur dioxide . Approximately 300,000 tons were produced in 1990. [ 4 ] The route using zinc powder is a two-step process:
The sodium borohydride method obeys the following stoichiometry:
Each equivalent of H − reduces two equivalents of sulfur dioxide. Formate has also been used as the reductant.
Sodium dithionite is stable when dry, but aqueous solutions deteriorate due to the following reaction:
This behavior is consistent with the instability of dithionous acid . Thus, solutions of sodium dithionite cannot be stored for a long period of time. [ 3 ]
Anhydrous sodium dithionite decomposes to sodium sulfate and sulfur dioxide above 90 °C in the air. In absence of air, it decomposes quickly above 150 °C to sodium sulfite , sodium thiosulfate , sulfur dioxide and trace amount of sulfur.
Sodium dithionite is a reducing agent. At pH 7, the potential is -0.66 V compared to the normal hydrogen electrode . Redox occurs with formation of bisulfite: [ 5 ]
Sodium dithionite reacts with oxygen:
These reactions exhibit complex pH-dependent equilibria involving bisulfite, thiosulfate, and sulfur dioxide.
In the presence of aldehydes, sodium dithionite reacts either to form α-hydroxy-sulfinates at room temperature or to reduce the aldehyde to the corresponding alcohol above a temperature of 85 °C. [ 6 ] [ 7 ] Some ketones are also reduced under similar conditions.
Sodium dithionite is used as a water-soluble reducing agent in some industrial dyeing processes. In the case of sulfur dyes and vat dyes , an otherwise water-insoluble dye can be reduced into its water-soluble alkali metal leuco salt . Indigo dye is sometimes processed in this way. [ 8 ]
Sodium dithionite can also be used for water treatment, aquarium water conditioners, gas purification, cleaning, and stripping.In addition to the textile industry, this compound is used in industries concerned with leather, foods, polymers, photography, and many others, often as a decolourising agent. It is even used domestically as a decoloring agent for white laundry, when it has been accidentally stained by way of a dyed item slipping into the high temperature washing cycle. It is usually available in 5 gram sachets termed hydrosulfite after the antiquated name of the salt.
It is the active ingredient in "Iron Out Rust Stain Remover", a commercial rust product. [ 9 ]
Sodium dithionite is often used in physiology experiments as a means of lowering solutions' redox potential (E o' -0.66 V vs SHE at pH 7). [ 10 ] Potassium ferricyanide is usually used as an oxidizing chemical in such experiments (E o' ~ .436 V at pH 7). In addition, sodium dithionite is often used in soil chemistry experiments to determine the amount of iron that is not incorporated in primary silicate minerals . Hence, iron extracted by sodium dithionite is also referred to as "free iron."
Aqueous solutions of sodium dithionite were once used to produce ' Fieser's solution' for the removal of oxygen from a gas stream. [ 11 ] Pyrithione can be prepared in a two-step synthesis from 2-bromopyridine by oxidation to the N -oxide with a suitable peracid followed by substitution using sodium dithionite to introduce the thiol functional group . [ 12 ]
It is used in Kodak fogging developer, FD-70. This is used in the second step in processing black and white positive images, for making slides. It is part of the Kodak Direct Positive Film Developing Outfit . [ 13 ]
The wide use of sodium dithionite is attributable in part to its low toxicity LD 50 at 2.5 g/kg (rats, oral). [ 4 ] | https://en.wikipedia.org/wiki/Sodium_dithionite |
Sodium dithiophosphate is the salt with the formula Na 3 PS 2 O 2 . It is usually supplied as the hydrated solid or as an aqueous solution together with other thiophosphates such as sodium monothiophosphate and sodium trithiophosphate . It is a colorless compound, but commercial samples can appear dark owing to the presence of impurities. It is used to facilitate the isolation of molybdenum from its ores.
The compound has been prepared in a multistep process starting with the base hydrolysis of phosphorus pentasulfide : [ 1 ]
The salt is isolated as the hydrate Na 3 PO 2 S 2 . (H 2 O) 11 . It is prone to hydrolysis, especially when it is heated as an aqueous solutions:
Its structure has been examined by X-ray crystallography . [ 2 ] [ 3 ]
This salt is used as a flotation agent in the purification of molybdenite (MoS 2 ) from other components of the ores, where it is usually known as " Nokes reagent " (after Charles M. Nokes, who patented it in 1948 [ 4 ] ). The salt is generated by the reaction of phosphorus pentasulfide with sodium hydroxide , often using impure reagents to obtain a mixture of the desired salt and related thiophosphates and oxidized species. Molybdenite particles, which are normally hydrophobic , become hydrophilic in the presence of this salt. In this context, the Nokes reagent is called a "depressant," because it suppresses the flotation tendency of the solids other than molybdenite. [ 5 ] [ 6 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sodium_dithiophosphate |
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/Sodium_dodecyl_sulfate |
Sodium ethyl xanthate ( SEX ) [ 3 ] is an organosulfur compound with the chemical formula CH 3 CH 2 OCS 2 Na . It is a pale yellow powder, which is usually obtained as the dihydrate. Sodium ethyl xanthate is used in the mining industry as a flotation agent . [ 4 ] A closely related potassium ethyl xanthate (KEX) is obtained as the anhydrous salt.
Akin to the preparation of most xanthates , sodium ethyl xanthate can be prepared by treating sodium ethoxide with carbon disulfide : [ 5 ] CH 3 CH 2 ONa + CS 2 → CH 3 CH 2 OCS 2 Na
Sodium ethyl xanthate is a pale yellow powder. Its aqueous solutions are stable at high pH if not heated. It rapidly hydrolyses at pH less than 9 at 25 °C. It is the conjugate base of the ethyl xanthic acid , a strong acid with p K a of 1.6 and p K b estimated as 12.4 for the conjugate base . [ 6 ] Sodium ethyl xanthate easily adsorbs on the surface of many sulfide minerals, [ 2 ] a key step in froth flotation .
Xanthates are susceptible to hydrolysis and oxidation [ 7 ] at low pH:
Oxidation gives diethyl dixanthogen disulfide :
Sodium ethyl xanthate can be identified through optical absorption peaks in the infrared (1179, 1160, 1115, 1085 cm −1 ) and ultraviolet (300 nm) ranges. There are at least six chemical detection methods:
Sodium ethyl xanthate can also be quantified using gravimetry , by weighing the lead xanthate residue obtained after reacting SEX with 10% solution of lead nitrate . There are also several electrochemical detection methods, which can be combined with some of the above chemical techniques. [ 9 ]
Sodium ethyl xanthate is used in the mining industry as flotation agent for recovery of metals, such as copper, nickel, silver or gold, as well as solid metal sulfides or oxides from ore slurries . This application was introduced by Cornelius H. Keller in 1925. Other applications include defoliant , herbicide , and an additive to rubber to protect it against oxygen and ozone. [ 10 ]
In 2000, Australia produced up to 10,000 tonnes of sodium ethyl xanthate and imported about 6,000 tonnes, mostly from China. [ 11 ] The material produced in Australia is the so-called 'liquid sodium ethyl xanthate' that refers to a 40% aqueous solution of the solid. [ 12 ] It is obtained by treating carbon disulfide with sodium hydroxide and ethanol. [ 13 ] Its density is 1.2 g/cm 3 and the freezing point is −6 °C. [ 14 ]
Sodium ethyl xanthate has moderate oral and dermal toxicity in animals and is irritating to eyes and skin. [ 13 ] It is especially toxic to aquatic life and therefore its disposal is strictly controlled. [ 15 ] Median lethal dose for (male albino mice, oral, 10% solution at pH~11) is 730 mg/kg of body weight, with most deaths occurring in the first day. The most affected organs were the central nervous system, liver and spleen . [ 16 ]
Since 1993, sodium ethyl xanthate is classified as a Priority Existing Chemical in Australia, meaning that its manufacture, handling, storage, use or disposal may result in adverse health or environment effects. This decision was justified by the widespread use of the chemical in industry and its decomposition to the toxic and flammable carbon disulfide gas. From two examples of sodium ethyl xanthate spillage in Australia, one resulted in evacuation of 100 people and hospitalization of 6 workers who were exposed to the fumes. In another accident, residents of the spillage area complained of headache, dizziness, and nausea. [ 17 ] Consequently, during high-risk sodium ethyl xanthate handling operations, workers are required by the Australian regulations to be equipped with protective clothing, anti-static gloves, boots and full-face respirators or self-contained breathing apparatus . [ 18 ] | https://en.wikipedia.org/wiki/Sodium_ethyl_xanthate |
Sodium ferrate is a chemical compound with the formula Na 2 FeO 4 . It is a sodium salt of ferric acid that is very difficult to obtain. In most iron compounds, the metal has an oxidation state of +2 or +3. Ferric acid, with an oxidation state of +6, is extremely unstable and does not exist under normal conditions. Therefore, its salts, such as sodium ferrate, also tend to be unstable. Due to its high oxidation state, FeO 4 2- is a potent oxidizing agent . [ 1 ]
The synthesis of sodium ferrate(VI) appears to be very delicate due to the instability of ferrate resulting from its high oxidizing power.
The methods to synthesize ferrate(VI) are: thermal, chemical and electrochemical. The thermal method usually requires high temperatures (about 800 °C) and habitually has a low efficiency (50%). The chemical method is multiphase and requires a large number of chemical compounds. The electrochemical method, compared to the other two methods mentioned, has advantages such as the product purity, low solvent demand and the use of an electron which is known as a clean oxidant.
In this methodology, a solution containing Fe(III) is oxidized in the presence of NaOH and converted to Fe(VI)O 4 2- . However, this compound degrades rapidly, so additional steps such as "sequestration", washing and drying processes are necessary to obtain a more stable product. [ 2 ]
Another drawback encountered with this methodology is related to the isolation and acquisition of the dry product from the corresponding solution, due to the high solubility of Na 2 FeO 4 in a saturated NaOH solution. By modifying the production procedure in which chlorine gas is passed through a NaOH-saturated solution of trivalent iron, a dry compound containing 41.38% of Na 2 FeO 4 can be obtained. [ 3 ]
The wet oxidation method has been extensively used by several researchers to produce solid or liquid ferrate, especially sodium and potassium (VI) ferrate (Na 2 FeO 4 and K 2 FeO 4 ). Generally, it employs: either ferrous (Fe II ) or ferric (Fe III ) salts as the source of iron ions, calcium, sodium hypochlorite (Ca(ClO) 2 , NaClO), sodium thiosulfate (Na 2 S 2 O 3 ) or chlorine (Cl 2 ) as oxidizing agents and, finally, sodium hydroxide, sodium carbonate (NaOH, NaCO 3 ) or potassium hydroxide (KOH) to increase the pH of the solution. [ 4 ] [ 5 ]
The electrochemical method requires either the use of an anion dissolved in an electrolysis cell containing a strong alkaline solution (NaOH or KOH) or an inert electrode in an Fe(III) solution with an electric current producing the oxidation of iron to Fe(VI). [ 6 ] [ 7 ] [ 8 ] The basic principle is shown in equations 1-4.
Anode reaction:
Fe 0 (s) + OH − (aq) → FeO 4 2- (aq) + 4H 2 O (aq) + 6e − (1)
Cathode reaction:
3H 2 O (aq) → H 2 0 (g) + 4H 2 O (aq) + 6e − (2)
Overall reactions:
Fe 0 (s) + 2OH − (aq) → FeO 4 2- (aq) + 3H 2 0 (g) + 4H 2 O (aq) (3)
FeO 4 2- (aq) + 2Na + (aq) → Na 2 FeO 4(aq) (4)
The first electrochemical synthesis of ferrate(VI) was carried out around 1841, which is one of the easiest routes to obtain sodium ferrate from solutions without impurities. [ 9 ] Later, researchers have performed several experiments in different alkaline environments with various NaOH concentrations, different current densities, temperature, and electrolysis intervals. It was found that increasing temperature could increase the oxidation efficiency, but this behavior is only applicable up to a certain temperature (about 60 °C).
The intensity of the electric current, the material of the anode electrode, and the type and concentration of the electrolyte significantly affect the production of ferrate (VI). Large amounts of carbon in the anode electrode can also increase the efficiency of ferrate (VI) production. Efficiencies above 70% can be achieved using iron or silver electrodes containing 0.9% carbon. The best ferrate (VI) production data have been obtained using a 99.99% pure iron electrode at temperatures around 30 - 60 °C using alternating current (AC). [ 6 ] [ 7 ] [ 8 ]
Currently, two methodologies are known for the dry oxidation of sodium ferrate: [ citation needed ]
FeO 5 4- (aq) + 4H 2 O (aq) → FeO 4 2- (aq) (5)
Fe 2 O 3(s) + 3Na 2 O 2(s) → 2Na 2 FeO 4(s) + Na 2 O (s) (6)
Both methods are dangerous and difficult to handle due to the use of high temperatures and therefore the possible risk of explosions.
The physical properties of this compound can be described as similar to those of potassium ferrate: a dark crystalline solid that dissolves in water to form a reddish-violet solution. However, sodium ferrate has less viscosity than potassium ferrate. It is difficult to isolate in the solid state by traditional crystallisation methods, such as precipitation by heating/cooling, vapor diffusion, antisolvent, etc., due to the ease with which it decomposes.
Regarding its chemical properties, sodium ferrate is a very strong oxidant, stronger and more reactive than potassium ferrate. Its redox potential in acid medium reaches 2.2 V, which is stronger than commonly used compounds for water treatment such as ozone (2.08 V), hydrogen peroxide (1.78 V) or potassium permanganate (1.68 V). In addition, it can also act as a coagulant for unwanted pollution compounds in wastewater, causing them to precipitate as large particles without decomposing into toxic compounds. [ 1 ]
Due to its properties and the fact that it does not generate environmentally toxic by-products, sodium ferrate can be used in the water treatment process. In water treatment it can act as:
In addition, sodium ferrate can also remove the colour, odour and oils of polymers and plastics making it a suitable compound for recycling as well as an alternative to traditional processes such as aeration or spreading.
Sodium ferrate and its decomposition products are non-toxic. However, sodium ferrate in solid state should not be kept in contact with flammable organic compounds.
Sodium ferrate in solid state should be stored in a dark space, without access to air. Ideally, it should be stored in a vacuum or under an inert gas. Its
solutions can be handled under normal conditions, but should be stored cold and not for long periods of time. | https://en.wikipedia.org/wiki/Sodium_ferrate |
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/Sodium_fluoroacetate |
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/Sodium_formate |
The sodium fusion test , or Lassaigne's test , is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens , nitrogen , and sulfur , in an organic compound . It was developed by J. L. Lassaigne . [ 1 ]
The test involves heating the sample with sodium metal, "fusing" it with the sample. A variety of techniques has been described. The "fused" sample is plunged into water, and the qualitative tests are performed on the resultant solution for the respective possible constituents. [ 2 ] [ 3 ]
The halogens, nitrogen, and sulfur are covalently bonded to the organic compounds are converted to various sodium salts formed during the fusion. Typically proposed reactions are:
The fate of the hydrocarbon portion of the sample is disregarded.
The aqueous extract is called sodium fusion extract or Lassaigne's extract.
The sodium fusion extract is made alkaline by adding NaOH . To this mixture, freshly prepared FeSO 4 solution is added and boiled for some time and then cooled. A few drops of FeCl 3 are added and Prussian blue (bluish green) color forms due to formation of ferric ferrocyanide along with NaCl . This shows the presence of nitrogen in the organic compound. [ 4 ]
6 CN − + Fe 2 + ⟶ [ Fe ( CN ) 6 ] 4 − {\displaystyle {\ce {6CN- +Fe^2+ -> [Fe(CN)6]^4-}}}
3 [ Fe ( CN ) 6 ] 4 − + 4 Fe 3 + → xH 2 O Fe 4 [ Fe ( CN ) 6 ] 3 ⋅ xH 2 O {\displaystyle {\ce {{3[Fe(CN)6]}^{4-}+4Fe^{3}+->[{\ce {xH2O}}]Fe4[Fe(CN)6]3\cdot xH2O}}}
The sodium fusion extract is acidified with acetic acid and lead acetate is added to it. A black precipitate of lead sulfide indicates the presence of sulfur.
Freshly prepared sodium nitroprusside solution is added to the sodium fusion extract, turning the solution deep violet due to formation of sodium thionitroprusside . [ 4 ]
S 2 − + [ Fe ( CN ) 5 NO ] 2 − ⟶ [ Fe ( CN ) 5 NOS ] 4 − {\displaystyle {\ce {S^2- + [Fe(CN)5NO]^2- -> [Fe(CN)5NOS]^4-}}}
In case, both nitrogen and sulfur are present in an organic compound, sodium thiocyanate is formed which gives blood red color since there are no free cyanide ions.
Fe 3 + + SCN − ⟶ [ Fe ( SCN ) ] 2 + {\displaystyle {\ce {Fe^3+ + SCN- -> [Fe(SCN)]^2+}}}
The sodium fusion extract is boiled with concentrated HNO 3 followed by the addition of AgNO 3 solution which yields a white ( AgCl ) or yellow ( AgBr or AgI ) precipitate if halogen is present. [ 4 ]
NaX + AgNO 3 ⟶ AgX + NaNO 3 {\displaystyle {\ce {NaX + AgNO3 -> AgX + NaNO3}}}
Sodium peroxide is added to the compound to oxidise phosphorus to sodium phosphate . It is boiled with concentrated HNO 3 and then ammonium molybdate is added. A yellow precipitate ( ammonium phosphomolybdate ) indicates the presence of phosphorus. [ citation needed ]
Na 3 PO 4 + 3 HNO 3 ⟶ H 3 PO 4 + 3 NaNO 3 {\displaystyle {\ce {Na3PO4 + 3HNO3 -> H3PO4 + 3NaNO3}}}
H 3 PO 4 + 21 NaNO 3 + 12 ( NH 4 ) 2 MoO 4 ⟶ ( NH 4 ) 3 [ P ( Mo 3 O 10 ) 4 ] + 21 NH 4 NO 3 + 12 H 2 O {\displaystyle {\ce {H3PO4 + 21NaNO3 + 12(NH4)2MoO4 -> (NH4)3[P(Mo3 O10)4] + 21NH4NO3 + 12H2O}}}
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sodium_fusion_test |
Glassy sodium Graham's salt Hexasodium metaphosphate
Sodium hexametaphosphate ( SHMP ) is a salt of composition Na 6 [(PO 3 ) 6 ] . [ 3 ] Sodium hexametaphosphate of commerce is typically a mixture of metaphosphates (empirical formula: NaPO 3 ), of which the hexamer is one, and is usually the compound referred to by this name. Such a mixture is more correctly termed sodium polymetaphosphate. They are white solids that dissolve in water.
SHMP is used as a sequestrant and has applications within a wide variety of industries, including as a food additive in which it is used under the E number E452i. Sodium carbonate is sometimes added to SHMP to raise the pH to 8.0–8.6, which produces a number of SHMP products used for water softening and detergents .
A significant use for sodium hexametaphosphate is as a deflocculant in the production of clay-based ceramic particles. [ 4 ] [ 5 ] [ 6 ] [ 7 ] It is also used as a dispersing agent to break down clay and other soil types for soil texture assessment. [ 8 ]
It is used as an active ingredient in toothpastes as an anti-staining and tartar prevention ingredient. [ 9 ]
As a food additive, SHMP is used as an emulsifier . Artificial maple syrup, canned milk, cheese powders and dips, imitation cheese, whipped topping, packaged egg whites, roast beef, fish fillets, fruit jelly, frozen desserts, salad dressing, herring, breakfast cereal, ice cream, beer, and bottled drinks, among other foods, can contain SHMP. [ 10 ] [ 11 ] [ 12 ]
SHMP is used in Diamond Crystal brand Bright & Soft Salt Pellets for water softeners in a concentration of 0.03%. It is the only additive other than sodium chloride .
SHMP is prepared by heating monosodium orthophosphate to generate sodium acid pyrophosphate :
Subsequently, the pyrophosphate is heated to give the corresponding sodium hexametaphosphate:
followed by rapid cooling.
SHMP hydrolyzes in aqueous solution, particularly under acidic conditions and/or heat, to sodium trimetaphosphate and sodium orthophosphate . [ 13 ]
Sodium hexametaphosphate is the alkali salt of one of the series of polymetaphosphoric acids (acids formed by the polymerization of phosphate groups). [ 14 ] Hexametaphosphoric acid was first made in 1825 by the German chemist Johann Frederich Philipp Engelhart (1797-1853). [ 15 ] For his doctoral thesis, Engelhart intended to determine whether iron was responsible for the red color of blood. In order to purify his blood samples, Engelhart had found that he could coagulate the blood serum's albumin (dissolved proteins) by treating the blood with phosphoric acid. This contradicted the findings of the famous Swedish chemist Jöns Jacob Berzelius , who had stated that phosphoric acid did not coagulate water-soluble proteins such as egg white. [ 16 ] Berzelius and Engelhart collaborated with the intention of resolving the contradiction; they concluded that Engelhart had produced a new form of phosphoric acid simply by burning phosphorus in air and then dissolving the resulting substance in water. [ 17 ] However they did not determine the new acid's composition. That analysis was accomplished in 1833 by the Scottish chemist Thomas Graham , who named the sodium salt of the new acid "metaphosphate of soda". [ 18 ] Graham's findings were confirmed by the German chemists Justus von Liebig and Theodor Fleitmann . [ 19 ] In 1849 Fleitmann coined the name "hexametaphosphoric acid". [ 20 ] [ 21 ]
By 1956, chromatographic analysis of hydrolysates of Graham's salt (sodium polyphosphate) indicated the presence of cyclic anions containing more than four phosphate groups; [ 22 ] these findings were confirmed in 1961. [ 23 ] In 1963, the German chemists Erich Thilo and Ulrich Schülke succeeded in preparing sodium hexametaphosphate by heating anhydrous sodium trimetaphosphate. [ 24 ]
Sodium phosphates are recognized to have low acute oral toxicity . SHMP concentrations not exceeding 10,000 mg/L or mg/kg are considered protective levels by the EFSA and US FDA. Extreme concentrations of this salt may cause acute side effects from excessive blood serum concentrations of sodium, such as: “irregular pulse , bradycardia , and hypocalcemia ." [ 25 ] | https://en.wikipedia.org/wiki/Sodium_hexametaphosphate |
Sodium hexanitritocobaltate(III) is an inorganic compound with the formula Na 3 [Co(NO 2 ) 6 ] . The anion of this yellow-coloured salt consists of the transition metal nitrite complex [Co(NO 2 ) 6 ] 3− . It was a reagent for the qualitative test for potassium and ammonium ions. [ 2 ]
The compound is prepared by oxidation of cobalt(II) salts in the presence of sodium nitrite : [ 3 ]
Although the sodium cobaltinitrite is soluble in water, it forms the basis of a quantitative determination of potassium, thallium, and ammonium ions. Under the recommended reaction conditions the insoluble double salt, K 2 Na[Co(NO 2 ) 6 ]·H 2 O is precipitated and weighed. [ 4 ] [ page needed ] In geochemical analysis , sodium cobaltinitrite is used to distinguish alkali feldspars from plagioclase feldspars in thin section. [ 5 ] | https://en.wikipedia.org/wiki/Sodium_hexanitritocobaltate(III) |
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/Sodium_hydride |
Sodium hydrogen selenite is an inorganic chemical consisting of a ratio of one hydrogen , one sodium , three oxygen , and one selenium atom.
It is the sodium salt of the conjugate base of selenous acid . This compound finds therapeutic application for providing the essential trace element selenium. Its preparation involves reacting sodium hydroxide with selenium dioxide . [ 2 ] | https://en.wikipedia.org/wiki/Sodium_hydrogen_selenite |
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/Sodium_hydroxide |
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/Sodium_hypochlorite |
Sodium hypophosphite (NaPO 2 H 2 , also known as sodium phosphinate ) is the sodium salt of hypophosphorous acid and is often encountered as the monohydrate, NaPO 2 H 2 ·H 2 O. It is a solid at room temperature, appearing as odorless white crystals. It is soluble in water, and easily absorbs moisture from the air.
Sodium hypophosphite should be kept in a cool, dry place, isolated from oxidizing materials. It decomposes into phosphine which is irritating to the respiratory tract and disodium phosphate .
Like other hypophosphites , sodium hypophosphite can reduce metal ions back into base metal. This forms the basis for electroless nickel plating (Ni-P), which is its main industrial application. [ 2 ] With this method, a durable nickel-phosphorus film can coat objects with irregular surfaces, such as in avionics, aviation and the petroleum field.
Sodium hypophosphite is capable of reducing nickel ions in solution to metallic nickel on metal substrates as well as on plastic substrates. [ 3 ] The latter requires that the substrate is activated with fine particles of palladium. The resulting nickel deposit contains up to 15% phosphorus.
It has been investigated as a food additive .
The United States Drug Enforcement Administration designated sodium hypophosphite as a List I chemical under 21 CFR 1310.02 effective November 17, 2001, specifically mentioning the compound together with several other salts of hypophosphorous acid. [ 4 ] [ 5 ] | https://en.wikipedia.org/wiki/Sodium_hypophosphite |
Sodium ions ( Na + ) are necessary in small amounts for some types of plants , [ 1 ] but sodium as a nutrient is more generally needed in larger amounts [ 1 ] by animals , due to their use of it for generation of nerve impulses and for maintenance of electrolyte balance and fluid balance . In animals, sodium ions are necessary for the aforementioned functions and for heart activity and certain metabolic functions. [ 2 ] The health effects of salt reflect what happens when the body has too much or too little sodium.
Characteristic concentrations of sodium in model organisms are: 10 mM in E. coli , 30 mM in budding yeast, 10 mM in mammalian cell and 100 mM in blood plasma. [ 3 ]
Additionally, sodium ions are essential to several cellular processes. They are responsible for the co-transport of glucose in the sodium glucose symport, are used to help maintain membrane polarity with the help of the sodium potassium pump, and are paired with water to thin the mucus of the airway lumen when the active Cystic Fibrosis Transport Receptor moves chloride ions into the airway. [ 4 ]
The minimum physiological requirement for sodium is between 115 and 500 mg per day depending on sweating due to physical activity, and whether the person is adapted to the climate. [ 5 ] Sodium chloride is the principal source of sodium in the diet, and is used as seasoning and preservative, such as for pickling and jerky ; most of it comes from processed foods. [ 6 ] The Adequate Intake for sodium is 1.2 to 1.5 g per day, [ 7 ] but on average people in the United States consume 3.4 g per day, [ 8 ] [ 9 ] the minimum amount that promotes hypertension. [ 10 ] Note that salt contains about 39.3% sodium by mass [ 11 ] —the rest being chlorine and other trace chemicals; thus the Tolerable Upper Intake Level of 2.3 g sodium would be about 5.9 g of salt—about 1 teaspoon . [ 12 ] The average daily excretion of sodium is between 40 and 220 mEq. [ 13 ]
Normal serum sodium levels are between approximately 135 and 145 mEq /L (135 to 145 mmol/L). A serum sodium level of less than 135 mEq/L qualifies as hyponatremia , which is considered severe when the serum sodium level is below 125 mEq/L. [ 14 ] [ 15 ]
The renin–angiotensin system and the atrial natriuretic peptide indirectly regulate the amount of signal transduction in the human central nervous system , which depends on sodium ion motion across the nerve cell membrane, in all nerves. Sodium is thus important in neuron function and osmoregulation between cells and the extracellular fluid ; the distribution of sodium ions are mediated in all animals by sodium–potassium pumps , which are active transporter solute pumps , pumping ions against the gradient, and sodium-potassium channels. [ 16 ] Sodium channels are known to be less selective in comparison to potassium channels. Sodium is the most prominent cation in extracellular fluid: in the 15 L of extracellular fluid in a 70 kg human there is around 50 grams of sodium, 90% of the body's total sodium content.
Some potent neurotoxins , such as batrachotoxin , increase the sodium ion permeability of the cell membranes in nerves and muscles, causing a massive and irreversible depolarization of the membranes with potentially fatal consequences. However, drugs with smaller effects on sodium ion motion in nerves may have diverse pharmacological effects that range from anti-depressant to anti-seizure actions.
Since only some plants need sodium and those in small quantities, a completely plant-based diet will generally be very low in sodium. [ citation needed ] This requires some herbivores to obtain their sodium from salt licks and other mineral sources. The animal need for sodium is probably the reason for the highly conserved ability to taste the sodium ion as "salty." Receptors for the pure salty taste respond best to sodium; otherwise, the receptors respond only to a few other small monovalent cations ( Li + , NH + 4 and somewhat to K + ). The calcium ion (Ca 2+ ) also tastes salty and sometimes bitter to some people but, like potassium, can trigger other tastes.
Sodium ions play a diverse and important role in many physiological processes, acting to regulate blood volume , blood pressure , osmotic equilibrium and pH . [ 8 ]
In C4 plants , sodium is a micronutrient that aids in metabolism, specifically in regeneration of phosphoenolpyruvate (involved in the biosynthesis of various aromatic compounds, and in carbon fixation ) and synthesis of chlorophyll. [ 17 ] In others, it substitutes for potassium in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata. [ 18 ] Excess sodium in the soil limits the uptake of water due to decreased water potential , which may result in wilting; similar concentrations in the cytoplasm can lead to enzyme inhibition, which in turn causes necrosis and chlorosis. [ 19 ] To avoid these problems, plants developed mechanisms that limit sodium uptake by roots, store them in cell vacuoles , and control them over long distances; [ 20 ] excess sodium may also be stored in old plant tissue, limiting the damage to new growth. Though much how excess sodium loading in the xylem is yet to be determined. However, anti porter CHX21 can be attributed to active loading of sodium into the xylem. [ 21 ]
Sodium is the primary cation (positively charged ion) in extracellular fluids in animals and humans. These fluids, such as blood plasma and extracellular fluids in other tissues, bathe cells and carry out transport functions for nutrients and wastes. Sodium is also the principal cation in seawater, although the concentration there is about 3.8 times what it is normally in extracellular body fluids.
Although the system for maintaining optimal salt and water balance in the body is a complex one, [ 22 ] one of the primary ways in which the human body keeps track of loss of body water is that osmoreceptors in the hypothalamus sense a balance of sodium and water concentration in extracellular fluids. Relative loss of body water will cause sodium concentration to rise higher than normal, a condition known as hypernatremia . This ordinarily results in thirst. Conversely, an excess of body water caused by drinking will result in too little sodium in the blood ( hyponatremia ), a condition which is again sensed by the hypothalamus , causing a decrease in vasopressin hormone secretion from the posterior pituitary , and a consequent loss of water in the urine, which acts to restore blood sodium concentrations to normal.
Severely dehydrated persons, such as people rescued from ocean or desert survival situations, usually have very high blood sodium concentrations. These must be very carefully and slowly returned to normal, since too-rapid correction of hypernatremia may result in brain damage from cellular swelling, as water moves suddenly into cells with high osmolar content.
In humans, a high-salt intake was demonstrated to attenuate nitric oxide production. Nitric oxide (NO) contributes to vessel homeostasis by inhibiting vascular smooth muscle contraction and growth, platelet aggregation, and leukocyte adhesion to the endothelium. [ 23 ]
Because the hypothalamus / osmoreceptor system ordinarily works well to cause drinking or urination to restore the body's sodium concentrations to normal, this system can be used in medical treatment to regulate the body's total fluid content, by first controlling the body's sodium content. Thus, when a powerful diuretic drug is given which causes the kidneys to excrete sodium, the effect is accompanied by an excretion of body water (water loss accompanies sodium loss). This happens because the kidney is unable to efficiently retain water while excreting large amounts of sodium. In addition, after sodium excretion, the osmoreceptor system may sense lowered sodium concentration in the blood and then direct compensatory urinary water loss in order to correct the hyponatremic (low blood sodium) state.
The sodium-potassium pump works with the sodium and potassium leak channels to maintain the membrane potential between the cell and the extracellular space. Sodium moves down the concentration gradient from the cytosol into the extracellular matrix. Potassium moves down its concentration gradient from the extracellular matrix into the cytosol. In order to maintain the membrane potential, the sodium-potassium pump acts as a form of direct active transport where the hydrolysis of ATP to ADP and an inorganic phosphate at the P-type ATPase moves 3 potassium ions back out of the cell and 2 sodium ions into the cell. [ 4 ]
The sodium-potassium pump plays a large role in neural signaling due to the maintenance of cell membrane potential. This creates an action potential that causes the neurons to polarize and depolarize their membranes by opening and closing the voltage gated channels: this alters voltage potential and leads to neurotransmitter secretion and ultimately signal transmission. [ 24 ]
When the pump fails to function, patients are susceptible to illnesses like heart failure and chronic obstructive lung disease (COLD). Those who experienced an event of heart failure had on average, a 40% lower concentration of the sodium-potassium ATPase. This lack of polarization of the membrane leads to an inability of action potentials to propagate at their usual rate, leading to a lowered hear rate and potentially heart failure. [ 25 ] In COLD diagnoses, a majority of patients found to have a lowered amount of magnesium and potassium also had a decreased concentration of the sodium-potassium pump in skeletal and smooth muscle during respiratory failure. COLD is treatable in the short term by glucocorticoid which up-regulates the sodium-potassium pump, helping to support muscle endurance and increase muscle activity during these episodes of respiratory failure. [ 26 ]
In the sodium-glucose symporter , sodium moves down its concentration gradient to move glucose up its concentration gradient. Sodium has a greater concentration outside of the cell, and binds to the symporter, which is in its outward facing conformation. Once sodium is bound, glucose can bind from the extracellular space, causing the symporter to switch into the occluded formation (closed) before opening to the inside of the cell and releasing the two sodium ions and the one glucose molecule. Once both are released, the symporter re-orients itself to the outward facing conformation and the process starts all over again. [ 4 ] A major example of up-regulation of the sodium-glucose symporter is seen in patients with type 2 diabetes , where there is roughly a 3-4 fold up-regulation of the sodium-glucose symporter (SGLT1). This leads to an influx of glucose into the cell and results in hyperglycemia. [ 27 ]
The Cystic Fibrosis Transport Regulator (CFTR) works by binding two ATP to the A1 and A2, ATP-binding domain. This opens the CFTR channel and allows chloride ions to flow into the lungs and airway lumen. This influx of negatively charged chloride ions into the airway lumen causes sodium to move into the airway lumen to balance the negative charge. Water then moves in with the sodium to balance the osmotic pressure and ultimately leads to the thinning of mucus. In cases of Cystic Fibrosis, the CFTR is defective and only binds a single ATP, leading to the channel failing to open and preventing chloride ions from diffusing into the airway lumen. Since chloride ions cannot diffuse in, there is no movement of sodium into the airway lumen, and no need for water to move into the lumen, leading to thick mucus that clogs and infects the airway lumen. [ 4 ] | https://en.wikipedia.org/wiki/Sodium_in_biology |
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/Sodium_iodate |
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/Sodium_iodide |
Sodium lignosulfonate ( lignosulfonic acid , sodium salt ) is used in the food industry as a de-foaming agent for paper production and in adhesives for items that come in contact with food. It has preservative properties, and is used as an ingredient in animal feeds. It is also used for construction, ceramics, mineral powder, chemical industry, textile industry (leather), metallurgical industry, petroleum industry, fire-retardant materials, rubber vulcanization , organic polymerization . [ 1 ]
It is a pepsin inhibitor .
Vovac, J.A. et al., Arch. Int. Pharmacodyn. Ther., 1969, 177, 150 (pharmacol)
Alphin, R.S. et al., Experientia, 1972,28, 53 (pharmacol)
Sodium lignosulfonate is also known by the following names. | https://en.wikipedia.org/wiki/Sodium_lignosulfonate |
Sodium methylsulfinylmethylide (also called NaDMSO or dimsyl sodium ) is the sodium salt of dimethyl sulfoxide . It has the chemical formula C H 3 S ( O )CH − 2 Na + . This unusual salt has some uses in organic chemistry as a base and nucleophile .
Since the first publication in 1965 by Corey et al. , [ 2 ] a number of additional uses for this reagent have been identified. [ 3 ]
Sodium methylsulfinylmethylide is prepared by heating sodium hydride [ 4 ] or sodium amide [ 5 ] in DMSO [ 6 ]
The p K a of DMSO is 35, which leads NaDMSO to be a powerful Brønsted base . NaDMSO is used in the generation of phosphorus and sulfur ylides . [ 7 ] NaDMSO in DMSO is especially convenient in the generation of dimethyloxosulfonium methylide and dimethylsulfonium methylide . [ 2 ] [ 8 ]
NaDMSO condenses with esters ( 1 ) to form β-ketosulfoxides ( 2 ), which can be useful intermediates. [ 9 ] Reduction of β-ketosulfoxides with aluminium amalgam gives methyl ketones ( 3 ). [ 10 ] Reaction with alkyl halides followed by elimination gives α,β-unsaturated ketones ( 4 ). β-ketosulfoxides can also be used in the Pummerer rearrangement to introduce nucleophiles alpha to a carbonyl ( 5 ). [ 11 ] | https://en.wikipedia.org/wiki/Sodium_methylsulfinylmethylide |
Sodium molybdate , Na 2 MoO 4 , is useful as a source of molybdenum . [ 2 ] This white, crystalline salt is often encountered as the dihydrate, Na 2 MoO 4 ·2H 2 O.
Dissolution of MoO 3 in sodium hydroxide at 50–70 °C followed by crystallizing the filtered product. [ 3 ] If crystallized below 10 °C, the decahydrate forms. Above 10 °C, the dihydate crystallizes. The anhydrous salt is obtained by heating this product at 100 °C.
The agriculture industry uses 500 tons per year as a fertilizer. In particular, its use has been suggested for treatment of whiptail in broccoli and cauliflower in molybdenum-deficient soils. [ 4 ] [ 5 ] However, care must be taken because at a level of 0.3 ppm sodium molybdate can cause copper deficiencies in animals, particularly cattle. [ 3 ]
It is used in industry for corrosion inhibition , as it is a non-oxidizing anodic inhibitor. [ 3 ] The addition of sodium molybdate significantly reduces the nitrite requirement of fluids inhibited with nitrite-amine, and improves the corrosion protection of carboxylate salt fluids. [ 6 ] In industrial water treatment applications where galvanic corrosion is a potential due to bimetallic construction, the application of sodium molybdate is preferred over sodium nitrite . Sodium molybdate has the advantage in that the dosing of lower ppm's of molybdate allow for lower conductivity of the circulating water. Sodium molybdate at levels of 50-100 ppm offer the same levels of corrosion inhibition as sodium nitrite at levels of 800+ ppm. By utilizing lower concentrations of sodium molybdate, conductivity is kept at a minimum and thus galvanic corrosion potentials are decreased. [ 7 ]
When treated with sodium borohydride , molybdate is reduced to molybdenum(IV) oxide : [ 8 ]
Sodium molybdate reacts with the acids of dithiophosphates: [ 3 ]
which further reacts to form [MoO 3 (S 2 P(OR) 2 ) 4 ].
In aqueous solution, sodium molybdate features dissociated sodium ions and tetrahedral molybdate ( MoO 2− 4 ), which adopts a sulfate -like structure. The solid dihydrate material has a complex structure typical for alkali metal salts of oxyanions. The MoO 2− 4 subunits are tetrahedral with Mo-O distances near 178 pm . [ 3 ] [ 9 ]
Sodium molybdate supports the biosynthesis of molybdoenzymes, which are found in all higher forms of life. [ 10 ] The LC50 for freshwater fish ranges from 60 to 7630 mg/L. The toxicity of soluble molybdate to marine organisms has also been reported. [ 11 ] | https://en.wikipedia.org/wiki/Sodium_molybdate |
Sodium naphthalene is an organic salt with the chemical formula Na + [ C 10 H 8 ] − . In the research laboratory, it is used as a reductant in the synthesis of organic, organometallic , and inorganic chemistry. It is usually generated in situ. When isolated, it invariably crystallizes as a solvate with ligands bound to Na + . [ 1 ]
The alkali metal naphthalene salts are prepared by stirring the metal with naphthalene in an ethereal solvent, usually as tetrahydrofuran or dimethoxyethane . The resulting salt is dark green. [ 2 ] [ 3 ] [ 4 ] The anion is a radical , giving a strong EPR signal near g = 2.0. Its deep green color arises from absorptions centered at 463 and 735 nm.
Several solvates of sodium naphthalenide have been characterized by X-ray crystallography . The effects are subtle, the outer pair of CH−CH bonds contract by 3 pm and the other nine C−C bonds elongate by 2–3 pm. The net effect is that reduction weakens the bonding. [ 5 ] [ 6 ]
With a reduction potential near −2.5 V vs NHE , the naphthalene radical anion is a strong reducing agent . [ 1 ] It is capable of defluorinating PTFE and is commonly used for chemically etching PTFE to allow adhesion. [ 7 ]
The anion is strongly basic , and a typical degradation pathway involves reaction with water and related protic sources such as alcohols . These reactions afford dihydronaphthalene :
Alkali metal salts of the naphthalene radical anion are used to prepare complexes of naphthalene . [ 8 ] | https://en.wikipedia.org/wiki/Sodium_naphthalene |
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/Sodium_nitrate |
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/Sodium_nitrite |
Sodium orthovanadate is the inorganic compound with the chemical formula Na 3 V O 4 . It forms a dihydrate Na 3 VO 4 ·2H 2 O . Sodium orthovanadate is a salt of the VO 3− 4 oxyanion . It is a colorless, water-soluble solid. [ 2 ]
Sodium orthovanadate is produced by dissolving vanadium(V) oxide in a solution of sodium hydroxide :
The salt features tetrahedral VO 3− 4 anion centers linked to octahedral Na + cation sites. [ 3 ]
Like many oxometalates, orthovanadate is subject to a number of reactions, which have been analyzed by 51 V NMR studies . At high pH, VO 3− 4 ions exist in equilibrium with HVO 2− 4 . [ 4 ] At lower pH's, condensation ensues to give various polyoxovanadates. Ultimately, decavanadate is formed. [ 5 ]
Vanadates exhibit a variety of biological activities, in part because they serve as structural mimics of phosphates . [ 6 ] [ 7 ] It acts as a competitive inhibitor of ATPases , alkaline and acid phosphatases, and protein-phosphotyrosine phosphatases, [ 8 ] and its inhibitory effects can be reversed by dilution or the addition of ethylenediaminetetraacetic acid (EDTA). [ 9 ]
Orthovanadate is activated by boiling and adjusting pH to ~10; this depolymerizes decavanadate into the active inhibitor, monovanadate. [ 8 ] | https://en.wikipedia.org/wiki/Sodium_orthovanadate |
Sodium perborate are chemical compounds with chemical formula [Na + ] 2 [B 2 O 4 (OH) 4 ] 2− (H 2 O) x . Commonly encountered salts are the anhydrous form (x = 0) and as a hexahydrate (x = 6). These two species are sometimes called, respectively, "monohydrate" or PBS-1 and "tetrahydrate" or PBS-4 , after the historic assumption that NaBO 3 would be the anhydrous form). [ 2 ] Both the anhydrous and hexahydrate salts are white, odorless, water-soluble solids. [ 3 ]
Peroxyborates are widely used in laundry detergents , as one of the peroxide-based bleaches .
Sodium perborate was first obtained in 1898, independently, by Sebastian Tanatar and by P. Melikoff and L. Pissadewsky; the researchers prepared sodium perborate by treating sodium borate with a solution of hydrogen peroxide and sodium hydroxide, but Tanatar also obtained sodium perborate by electrolysis of a solution of sodium borate. [ 4 ] [ 5 ] [ 6 ]
Unlike sodium percarbonate , the peroxyborates are not adducts of hydrogen peroxide. [ 7 ] [ 1 ] Rather, they contain a peroxyborate anion [(B(OH) 2 OO) 2 ] 2− , which consists of a cyclic −B−O−O−B−O−O− core with a pair of hydroxy groups bonded to each boron atom. The ring adopts a chair conformation . [ 8 ] The hexahydrate has the formula Na 2 H 4 B 2 O 8 ·6H 2 O , that is, Na 2 H 16 B 2 O 14 or NaH 8 BO 7 . [ 9 ]
The anhydrous compound is commonly but incorrectly called a "monohydrate" with the historical but misleading formula NaBO 3 ·H 2 O . Instead, a more descriptive formula is Na 2 [(HO) 2 B] 2 (O 2 ) 2 . Likewise, the hexahydrate is usually called "tetrahydrate" and formulated as NaBO 3 ·4H 2 O . [ 2 ] Both forms are white, odorless, water-soluble solids. [ 3 ] The "monohydrate" and the "tetrahydrate" are the commercially important forms. [ 3 ]
A true tetrahydrate Na 2 H 4 B 2 O 8 ·4H 2 O , traditionally known as the "trihydrate", is also known but has no industrial significance. There is a CAS number for each of the three traditional "hydrates", the three "peroxyborate" versions of each (interpreted as a hydrogen peroxide adduct) and the poorly-defined "anhydrate" NaBO 3 , a total of seven. [ 1 ]
Sodium perborate hydrolyzes (i.e. breaks down in contact with water), producing hydrogen peroxide and borate : [ 3 ]
The resulting hydroperoxide then enter in equilibrium with boric acid B(OH) 3 , hydrogen peroxide H 2 O 2 , the hydroperoxyl anion − OOH , and the tetrahydroxyborate anion [B(OH) 4 ] − : [ 2 ]
As the concentration of the solution increases, other peroxoborate species become significant. With excess H 2 O 2 , the anions [B(OH) 2 (OOH) 2 ] − , [B(OH)(OOH) 3 ] − , and eventually [B(OOH) 4 ] − appear. At high borate concentrations, the sodium perborate with dimeric anion crystallizes out, due to its relatively low solubility. [ 2 ]
The "monohydrate" form dissolves faster than the "tetrahydrate" and has higher heat stability; it is prepared by heating the "tetrahydrate". [ 1 ] The commercial "anhydrate", or Oxoborate , is prepared by further heating of "monohydrate" and actually consists of sodium borate and boron–oxygen radical. [ 1 ]
Sodium perborate is manufactured by reaction of borax Na 2 B 4 O 7 and sodium hydroxide NaOH to give sodium metaborate NaBO 2 , which is then reacted with hydrogen peroxide to give hydrated sodium perborate: [ 3 ] [ 10 ]
A surfactant may be added to control crystal size. [ 11 ] [ 12 ]
It may also be produced in the electrolysis of an aqueous solution containing borax, sodium carbonate and sodium bicarbonate (potassium dichromate is added to improve yield along with sodium silicate). A copper pipe is used as a cathode and platinum for the anode, the current being 6 amperes at 7 to 8 volts, and the temperature 10 °C. [ 13 ]
Sodium perborate serves as a stable source of active oxygen in many detergents , laundry detergents , cleaning products , and laundry bleaches . [ 3 ] It is a less aggressive bleach than sodium hypochlorite and other chlorine-based bleaches , causing less degradation to dyes and textiles . Sodium perborate releases oxygen rapidly at temperatures greater than 60 °C. Addition of the activator, typically tetraacetylethylenediamine (TAED), makes it active at lower temperatures (40–60 °C).
The compound has antiseptic properties and can act as a disinfectant . It is also used as a "disappearing" preservative in some brands of eye drops . [ citation needed ]
Sodium perborate monohydrate is quickly hydrolyzed into hydrogen peroxide and borate on contact with water. [ 3 ] A 1979 double-blind crossover study [ 14 ] suggests that hydrogen peroxide , which is released during the use of this product, may prevent or retard colonization and multiplication of anaerobic bacteria, such as those that inhabit oral wounds.
Sodium perborate is also present in some tooth bleaching formulas for non vital root treated teeth. The compound is inserted in the root canal and left in place for an extended period of time to allow it to diffuse into the tooth and bleach stains from the inside out. However, this use has been banned in the European Union . [ 15 ]
Sodium perborate is also used as an oxidizing reagent in organic synthesis . For example, it converts thioethers into sulfoxides and sulfones . [ 16 ] Another use of sodium perborate in organic synthesis is as a convenient alternative to H 2 O 2 , for example in the 2 step conversion of an aryl halide to a phenol (the first step is a Miyaura borylation ). [ 17 ]
In the European Union , sodium perborate, like most perborates, was classified as "carcinogenic, mutagenic, or toxic for reproduction" (CMR), category 1B of Regulation (EC) 790/2009, as a result of being included in Part 3 of Annex VI of the regulation 1272/2008 on Classification, Labelling and Packaging (CLP) of substances and mixtures. As a result, their use has been automatically banned in cosmetic products in the EU, in any concentration, starting 1 December 2010. That extends to the use of perborates for tooth whitening. [ 18 ] [ 15 ]
Bocasan was an oral wound cleanser manufactured in the United Kingdom by Knox Laboratories Ltd of London from 1960–1975, [ 19 ] before being rebranded as an Oral-B product [ 20 ]
Production of Bocasan appears to have ceased by 2003. A similar product, Amosan was available for a period before also ceasing production in 2010. As of 2013, a Dutch pharmacy offers the same formulation under the name Bikosan [ 21 ]
It was used to aid treatment, in adults or children over 5 years old, of periodontal conditions such as canker sores , denture irritation , orthodontic irritation, or after dental procedures.
Bocasan was packaged in a 1.7 gram envelope, and contained 69.72% sodium perborate monohydrate and 29.68% sodium hydrogen tartrate anhydrous. To use, the contents were dissolved in 30 cubic centimetres of warm water. Half the amount was swilled around the mouth for two minutes and discarded, and the procedure repeated with the remainder. Treatment was recommended three times a day after meals.
A 1979 double-blind crossover study [ 22 ] suggests that hydrogen peroxide , which is released during the use of this product, may prevent or retard colonization and multiplication of anaerobic bacteria, such as those that inhabit oral wounds. A small (n=12) 1998 RCT shows that Bocasan combined with chlorhexidine mouthwash is better than chlorhexidine alone in preventing plaque. [ 23 ] A further study (n=28) shows that Bocasan reduces the staining associated with chlorhexidine. [ 24 ]
Amosan [ 25 ] is an oral antiseptic rinse . It contains 68.635% sodium perborate monohydrate by weight. Sold as a powder customarily packaged in 1.7g envelopes, it reconstitution with warm water, after which it is used as a mouth rinse. It is used to aid in the prevention of, as well as speed the recovery from canker sores , denture irritation , orthodontic irritation, and oral injuries or after dental procedures.
Amosan was originally made by Oral-B ; a mention of the powder appeared in the February 6, 1970 Federal Register . [ 26 ] Between 2005 and 2010, Amosan was manufactured in Belgium and sold under the Oral-B brand, belonging to Procter & Gamble after its 2005 acquisition of Gillette. In December 2010, its use was banned in the EU, as the product is based on borate, which the union considers "carcinogenic, mutagenic, or toxic for reproduction". [ 15 ]
Vintage Brands Limited began manufacturing and selling Amosan Oral Antiseptic Rinse in 2014 because many consumers were disappointed that it was no longer available. [ 27 ] Product review pages on Amazon [ 28 ] and public comment forums elsewhere [ 29 ] indicate a high level of frustration with the discontinuation by users who could find no effective alternative treatment.
In April 2012, it was reported that Shoppers Drug Mart in Canada had produced a comparable product under their house brand: 'Life Brand Oral Wound Cleanser'. [ 30 ] Also, Jean Coutu and Rexall has their own house brand versions. | https://en.wikipedia.org/wiki/Sodium_perborate |
Sodium percarbonate or sodium carbonate peroxide is an inorganic compound with the formula 2 Na 2 CO 3 · 3 H 2 O 2 . It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate ). It is a colorless, crystalline, hygroscopic , and water-soluble solid. [ 3 ] It is sometimes abbreviated as SPC . It contains 32.5% by weight of hydrogen peroxide.
The product is used in some eco-friendly bleaches and other cleaning products . [ 3 ]
Sodium percarbonate was first prepared in 1899 by Ukrainian chemist Sebastian Moiseevich Tanatar (7 October 1849 – 30 November 1917). [ 4 ]
At room temperature, solid sodium percarbonate has the orthorhombic crystal structure , with the Cmca crystallographic space group . The structure changes to Pbca as the crystals are cooled below about −30 °C. [ 1 ]
Dissolved in water, sodium percarbonate yields a mixture of hydrogen peroxide, sodium cations ( Na + ), and carbonate ( CO 2− 3 ). [ 3 ] [ 5 ]
Sodium percarbonate is produced industrially by crystallization of a solution of sodium carbonate and hydrogen peroxide, with attention to the pH and concentrations. [ 6 ] [ 1 ] [ 7 ] This method is also convenient for the laboratory preparation. Alternatively, dry sodium carbonate may be treated directly with concentrated hydrogen peroxide solution. [ 8 ]
World production capacity of this compound was estimated at several hundred thousand tons for 2004. [ 9 ]
As an oxidizing agent , sodium percarbonate is an ingredient in a number of home and laundry cleaning products, including non-chlorine bleach products such as Oxyper , OxiClean , Tide laundry detergent , [ 3 ] and Vanish . [ 5 ]
Many commercial products mix a percentage of sodium percarbonate with sodium carbonate. The average "Oxy" product in the supermarket contains 35–40% sodium percarbonate with about 5% active oxygen when titrated.
Sodium percarbonate is also used as a cleaning agent in homebrewing . [ 10 ]
Sodium percarbonate can be used in organic synthesis as a convenient source of anhydrous H 2 O 2 , in particular in solvents that cannot dissolve the carbonate but can leach the H 2 O 2 out of it. [ 11 ] A method for generating trifluoroperacetic acid in situ for use in Baeyer–Villiger oxidations from sodium percarbonate and trifluoroacetic anhydride has been reported; it provides a convenient and cheap approach to this reagent without the need to obtain highly concentrated hydrogen peroxide. [ 12 ] [ 13 ] | https://en.wikipedia.org/wiki/Sodium_percarbonate |
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/Sodium_perchlorate |
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/Sodium_periodate |
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/Sodium_permanganate |
Sodium peroxide is an inorganic compound with the formula Na 2 O 2 . This yellowish solid is the product of sodium ignited in excess oxygen. [ 3 ] It is a strong base. This metal peroxide exists in several hydrates and peroxyhydrates including Na 2 O 2 ·2H 2 O 2 ·4H 2 O, Na 2 O 2 ·2H 2 O, Na 2 O 2 ·2H 2 O 2 , and Na 2 O 2 ·8H 2 O. [ 4 ] The octahydrate, which is simple to prepare, is white, in contrast to the anhydrous material. [ 5 ]
Sodium peroxide crystallizes with hexagonal symmetry. [ 6 ] Upon heating, the hexagonal form undergoes a transition into a phase of unknown symmetry at 512 °C. [ 7 ] With further heating above the 657 °C boiling point, the compound decomposes to Na 2 O, releasing O 2 . [ 8 ]
Commercially, sodium peroxide is produced from the elements in a two-stage process. First sodium is oxidized to sodium oxide : [ 7 ] [ 9 ]
Subsequently, this oxide is treated with more oxygen:
This was the method by which the substance was discovered in 1810 by Joseph Louis Gay-Lussac and Louis Jacques Thénard , as well as how it was for the first time commercially made by Hamilton Castner in the 1890s. [ 10 ]
It may also be produced by passing ozone gas over solid sodium iodide inside a platinum or palladium tube. The ozone oxidizes the sodium to form sodium peroxide. The iodine can be sublimed by mild heating. The platinum or palladium catalyzes the reaction and is not attacked by the sodium peroxide.
The octahydrate can be produced by treating sodium hydroxide with hydrogen peroxide. [ 5 ]
Sodium peroxide hydrolyzes to give sodium hydroxide and hydrogen peroxide according to the reaction [ 9 ]
Sodium peroxide was used to bleach wood pulp for the production of paper and textiles. Presently it is mainly used for specialized laboratory operations, e.g., the extraction of minerals from various ores. Sodium peroxide may go by the commercial names of Solozone [ 7 ] and Flocool . [ 8 ] In chemistry preparations, sodium peroxide is used as an oxidizing agent. It is also used as an oxygen source by reacting it with carbon dioxide to produce oxygen and sodium carbonate :
It is thus particularly useful in scuba gear, submarines, etc. Lithium peroxide and potassium superoxide have similar uses.
Sodium peroxide was once used on a large scale for the production of sodium perborate , but alternative routes to that cleaning agent have been developed. [ 4 ] | https://en.wikipedia.org/wiki/Sodium_peroxide |
Sodium peroxycarbonate or sodium percarbonate , sodium permonocarbonate is a chemical compound , a peroxycarbonate of sodium , with formula Na 2 CO 4 [ 1 ]
This article about chemical compounds is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sodium_peroxycarbonate |
Sodium persulfate is the inorganic compound with the formula Na 2 S 2 O 8 . It is the sodium salt of peroxydisulfuric acid , H 2 S 2 O 8 , an oxidizing agent . It is a white solid that dissolves in water. It is almost non- hygroscopic and has good shelf-life.
The salt is prepared by the electrolytic oxidation of sodium bisulfate :
Oxidation is conducted at a platinum anode. [ 2 ] In this way about 165,000 tons were produced in 2005. [ 3 ]
The standard redox potential of sodium persulfate into hydrogen sulfate is 2.1 V, which is higher than that of hydrogen peroxide (1.8 V) but lower than ozone (2.2 V). [ 4 ] The sulfate radical formed in situ has a standard electrode potential of 2.7 V.
However, there are a few drawbacks in utilizing platinum anodes to produce the salts; the manufacturing process is inefficient due to oxygen evolution and the product could contain contaminants coming from platinum corrosion (mainly due to extremely oxidizing nature of the sulfate radical). Thus, boron-doped diamond electrodes have been proposed as alternatives to the conventional platinum electrodes. [ 5 ]
The sodium and potassium salts adopt very similar structures in the solid state, according to X-ray crystallography . In the sodium salt, the O-O distance is 1.476 Å. The sulfate groups are tetrahedral, with three short S-O distances near 1.44 and one long S-O bond at 1.64 Å. [ 1 ]
It is mainly used as a radical initiator for emulsion polymerization reactions for styrene based polymers such as Acrylonitrile butadiene styrene . [ 3 ] Also applicable for accelerated curing of low formaldehyde adhesives.
It is a bleach , both standalone (particularly in hair cosmetics) and as a detergent component. It is a replacement for ammonium persulfate in etching mixtures for zinc and printed circuit boards , and is used for pickling of copper and some other metals.
It is also used as a soil conditioner and for soil and groundwater remediation [ 5 ] [ 6 ] and in manufacture of dyestuffs , modification of starch , bleach activator , desizing agent for oxidative desizing, etc.
Sodium persulfate is a specialized oxidizing agent in chemistry , classically in the Elbs persulfate oxidation and the Boyland–Sims oxidation reactions. It is also used in radical reactions; for example in a synthesis of diapocynin from apocynin where iron(II) sulfate is the radical initiator. [ 7 ]
The salt is an oxidizer and forms combustible mixtures with organic materials such as paper. | https://en.wikipedia.org/wiki/Sodium_persulfate |
Sodium sulfate (also known as sodium sulphate or sulfate of soda ) is the inorganic compound with formula Na 2 SO 4 as well as several related hydrates . All forms are white solids that are highly soluble in water. With an annual production of 6 million tonnes , the decahydrate is a major commodity chemical product. It is mainly used as a filler in the manufacture of powdered home laundry detergents and in the Kraft process of paper pulping for making highly alkaline sulfides . [ 3 ]
The decahydrate of sodium sulfate is known as Glauber's salt after the Dutch – German chemist and apothecary Johann Rudolf Glauber (1604–1670), who discovered it in Austrian spring water in 1625. He named it sal mirabilis (miraculous salt), because of its medicinal properties: the crystals were used as a general-purpose laxative , until more sophisticated alternatives came about in the 1900s. [ 4 ] [ 5 ] However, J. Kunckel later alleged that it was known as a secret medicine in Saxony already in the mid-16th century. [ 6 ]
In the 18th century, Glauber's salt began to be used as a raw material for the industrial production of soda ash ( sodium carbonate ), by reaction with potash ( potassium carbonate ). Demand for soda ash increased, and the supply of sodium sulfate had to increase in line. Therefore, in the 19th century, the large-scale Leblanc process , producing synthetic sodium sulfate as a key intermediate, became the principal method of soda-ash production. [ 7 ]
Sodium sulfate is a typical electrostatically bonded ionic sulfate. The existence of free sulfate ions in solution is indicated by the easy formation of insoluble sulfates when these solutions are treated with Ba 2+ or Pb 2+ salts:
Sodium sulfate is unreactive toward most oxidizing or reducing agents . At high temperatures, it can be converted to sodium sulfide by carbothermal reduction (aka thermo-chemical sulfate reduction (TSR), high temperature heating with charcoal, etc.): [ 8 ]
This reaction was employed in the Leblanc process , a defunct industrial route to sodium carbonate .
Sodium sulfate reacts with sulfuric acid to give the acid salt sodium bisulfate : [ 9 ] [ 10 ]
Sodium sulfate displays a moderate tendency to form double salts . The only alums formed with common trivalent metals are NaAl(SO 4 ) 2 (unstable above 39 °C) and NaCr(SO 4 ) 2 , in contrast to potassium sulfate and ammonium sulfate which form many stable alums. [ 11 ] Double salts with some other alkali metal sulfates are known, including Na 2 SO 4 ·3K 2 SO 4 which occurs naturally as the mineral aphthitalite . Formation of glaserite by reaction of sodium sulfate with potassium chloride has been used as the basis of a method for producing potassium sulfate , a fertiliser . [ 12 ] Other double salts include 3Na 2 SO 4 ·CaSO 4 , 3Na 2 SO 4 ·MgSO 4 ( vanthoffite ) and NaF·Na 2 SO 4 . [ 13 ]
Sodium sulfate has unusual solubility characteristics in water. [ 14 ] Its solubility in water rises more than tenfold between 0 °C and 32.384 °C, where it reaches a maximum of 49.7 g/100 mL. At this point the solubility curve changes slope, and the solubility becomes almost independent of temperature. This temperature of 32.384 °C, corresponding to the release of crystal water and melting of the hydrated salt, serves as an accurate temperature reference for thermometer calibration .
Crystals of the decahydrate consist of [Na(OH 2 ) 6 ] + ions with octahedral molecular geometry . These octahedra share edges such that 8 of the 10 water molecules are bound to sodium and 2 others are interstitial, being hydrogen-bonded to sulfate. These cations are linked to the sulfate anions by hydrogen bonds . The Na–O distances are about 240 pm . [ 15 ] Crystalline sodium sulfate decahydrate is also unusual among hydrated salts in having a measurable residual entropy (entropy at absolute zero ) of 6.32 J/(K·mol). This is ascribed to its ability to distribute water much more rapidly compared to most hydrates. [ 16 ]
The world production of sodium sulfate, almost exclusively in the form of the decahydrate, amounts to approximately 5.5 to 6 million tonnes annually (Mt/a). In 1985, production was 4.5 Mt/a, half from natural sources, and half from chemical production. After 2000, at a stable level until 2006, natural production had increased to 4 Mt/a, and chemical production decreased to 1.5 to 2 Mt/a, with a total of 5.5 to 6 Mt/a. [ 17 ] [ 18 ] [ 19 ] [ 20 ] For all applications, naturally produced and chemically produced sodium sulfate are practically interchangeable.
Two thirds of the world's production of the decahydrate (Glauber's salt) is from the natural mineral form mirabilite , for example as found in lake beds in southern Saskatchewan . In 1990, Mexico and Spain were the world's main producers of natural sodium sulfate (each around 500,000 tonnes ), with Russia , United States , and Canada around 350,000 tonnes each. [ 18 ] Natural resources are estimated at over 1 billion tonnes. [ 17 ] [ 18 ]
Major producers of 200,000 to 1,500,000 tonnes/year in 2006 included Searles Valley Minerals (California, US), Airborne Industrial Minerals (Saskatchewan, Canada), Química del Rey (Coahuila, Mexico), Minera de Santa Marta and Criaderos Minerales Y Derivados, also known as Grupo Crimidesa (Burgos, Spain), Minera de Santa Marta (Toledo, Spain), Sulquisa (Madrid, Spain), Chengdu Sanlian Tianquan Chemical ( Tianquan County , Sichuan, China), Hongze Yinzhu Chemical Group ( Hongze District , Jiangsu, China), Nafine Chemical Industry Group [ zh ] (Shanxi, China), Sichuan Province Chuanmei Mirabilite ( 万胜镇 [ zh ] , Dongpo District , Meishan , Sichuan, China), and Kuchuksulphat JSC (Altai Krai, Siberia, Russia). [ 17 ] [ 19 ]
Anhydrous sodium sulfate occurs in arid environments as the mineral thénardite . It slowly turns to mirabilite in damp air. Sodium sulfate is also found as glauberite , a calcium sodium sulfate mineral. Both minerals are less common than mirabilite. [ citation needed ]
About one third of the world's sodium sulfate is produced as by-product of other processes in chemical industry. Most of this production is chemically inherent to the primary process, and only marginally economical. By effort of the industry, therefore, sodium sulfate production as by-product is declining.
The most important chemical sodium sulfate production is during hydrochloric acid production, either from sodium chloride (salt) and sulfuric acid , in the Mannheim process , or from sulfur dioxide in the Hargreaves process . [ 21 ] The resulting sodium sulfate from these processes is known as salt cake .
The second major production of sodium sulfate are the processes where surplus sodium hydroxide is neutralised by sulfuric acid to obtain sulfate ( SO 2− 4 ) by using copper sulfate (CuSO 4 ) (as historically applied on a large scale in the production of rayon by using copper(II) hydroxide ). This method is also a regularly applied and convenient laboratory preparation.
In the laboratory it can also be synthesized from the reaction between sodium bicarbonate and magnesium sulfate , by precipitating magnesium carbonate .
However, as commercial sources are readily available, laboratory synthesis is not practised often.
Formerly, sodium sulfate was also a by-product of the manufacture of sodium dichromate , where sulfuric acid is added to sodium chromate solution forming sodium dichromate, or subsequently chromic acid. Alternatively, sodium sulfate is or was formed in the production of lithium carbonate , chelating agents , resorcinol , ascorbic acid , silica pigments, nitric acid , and phenol . [ 17 ]
Bulk sodium sulfate is usually purified via the decahydrate form, since the anhydrous form tends to attract iron compounds and organic compounds . The anhydrous form is easily produced from the hydrated form by gentle warming.
Major sodium sulfate by-product producers of 50–80 Mt/a in 2006 include Elementis Chromium (chromium industry, Castle Hayne, NC, US), Lenzing AG (200 Mt/a, rayon industry, Lenzing, Austria), Addiseo (formerly Rhodia, methionine industry, Les Roches-Roussillon, France), Elementis (chromium industry, Stockton-on-Tees, UK), Shikoku Chemicals (Tokushima, Japan) and Visko-R (rayon industry, Russia). [ 17 ]
With US pricing at $30 per tonne in 1970, up to $90 per tonne for salt cake quality, and $130 for better grades, sodium sulfate is a very cheap material. The largest use is as filler in powdered home laundry detergents , consuming approximately 50% of world production. This use is waning as domestic consumers are increasingly switching to compact or liquid detergents that do not include sodium sulfate. [ 17 ]
Another formerly major use for sodium sulfate, notably in the US and Canada, is in the Kraft process for the manufacture of wood pulp . Organics present in the "black liquor" from this process are burnt to produce heat, needed to drive the reduction of sodium sulfate to sodium sulfide . However, due to advances in the thermal efficiency of the Kraft recovery process in the early 1960s, more efficient sulfur recovery was achieved and the need for sodium sulfate makeup was drastically reduced. [ 22 ] Hence, the use of sodium sulfate in the US and Canadian pulp industry declined from 1,400,000 tonnes per year in 1970 to only approx. 150,000 tonnes in 2006. [ 17 ]
The glass industry provides another significant application for sodium sulfate, as second largest application in Europe. Sodium sulfate is used as a fining agent , to help remove small air bubbles from molten glass. It fluxes the glass, and prevents scum formation of the glass melt during refining. The glass industry in Europe has been consuming from 1970 to 2006 a stable 110,000 tonnes annually. [ 17 ]
Sodium sulfate is important in the manufacture of textiles , particularly in Japan, where this is the largest application. Sodium sulfate is added to increase the ionic strength of the solution and so helps in "levelling", i.e. reducing negative electrical charges on textile fibres, so that dyes can penetrate evenly (see the theory of the diffuse double layer (DDL) elaborated by Gouy and Chapman ). Unlike the alternative sodium chloride , it does not corrode the stainless steel vessels used in dyeing. This application in Japan and US consumed in 2006 approximately 100,000 tonnes. [ 17 ]
Sodium sulfate is used as a diluent for food colours. [ 23 ] It is known as E number additive E514 .
The high heat-storage capacity in the phase change from solid to liquid, and the advantageous phase change temperature of 32 °C (90 °F) makes this material especially appropriate for storing low-grade solar heat for later release in space heating applications. In some applications the material is incorporated into thermal tiles that are placed in an attic space, while in other applications, the salt is incorporated into cells surrounded by solar–heated water. The phase change allows a substantial reduction in the mass of the material required for effective heat storage (the heat of fusion of sodium sulfate decahydrate is 82 kJ/mol or 252 kJ/kg [ 24 ] ), with the further advantage of a consistency of temperature as long as sufficient material in the appropriate phase is available.
For cooling applications, a mixture with common sodium chloride salt (NaCl) lowers the melting point to 18 °C (64 °F). The heat of fusion of NaCl·Na 2 SO 4 ·10H 2 O, is actually increased slightly to 286 kJ/kg. [ 25 ]
In the laboratory, anhydrous sodium sulfate is widely used as an inert drying agent , for removing traces of water from organic solutions. [ 26 ] It is more efficient, but slower-acting, than the similar agent magnesium sulfate . It is only effective below about 30 °C (86 °F), but it can be used with a variety of materials since it is chemically fairly inert. Sodium sulfate is added to the solution until the crystals no longer clump together; the two video clips (see above) demonstrate how the crystals clump when still wet, but some crystals flow freely once a sample is dry.
Glauber's salt, the decahydrate, is used as a laxative . It is effective for the removal of certain drugs, such as paracetamol (acetaminophen) from the body; thus it can be used after an overdose. [ 27 ] [ 28 ]
In 1953, sodium sulfate was proposed for heat storage in passive solar heating systems. This takes advantage of its unusual solubility properties, and the high heat of crystallisation (78.2 kJ/mol). [ 29 ]
Other uses for sodium sulfate include de-frosting windows, starch manufacture, as an additive in carpet fresheners, and as an additive to cattle feed.
At least one company, Thermaltake, makes a laptop computer chill mat (iXoft Notebook Cooler) using sodium sulfate decahydrate inside a quilted plastic pad. The material slowly turns to liquid and recirculates, equalizing laptop temperature and acting as an insulation. [ 30 ]
Although sodium sulfate is generally regarded as non-toxic, [ 23 ] it should be handled with care. The dust can cause temporary asthma or eye irritation; this risk can be prevented by using eye protection and a paper mask. Transport is not limited, and no Risk Phrase or Safety Phrase applies. [ 31 ] | https://en.wikipedia.org/wiki/Sodium_sulfate |
This page provides supplementary chemical data on sodium sulfate .
The handling of this chemical may incur notable safety precautions. It is highly recommend that you seek the Safety Data Sheet ( SDS ) for this chemical from the manufacturer and follow its directions. | https://en.wikipedia.org/wiki/Sodium_sulfate_(data_page) |
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/Sodium_superoxide |
Sodium tert -butoxide (or sodium t -butoxide ) is a chemical compound with the formula (CH 3 ) 3 CONa (abbr. NaOtBu ). [ 2 ] It is a strong, non-nucleophilic base . It is flammable and moisture sensitive. It is sometimes written in the chemical literature as sodium t -butoxide. It is similar in reactivity to the more common potassium tert -butoxide .
The compound can be produced by treating tert -butyl alcohol with sodium hydride . [ 3 ]
One application for sodium tert -butoxide is as a non-nucleophilic base. It has been widely used in the Buchwald–Hartwig amination , as in this typical example: [ 4 ]
Sodium tert-butoxide is used to prepare tert-butoxide complexes. For example hexa(tert-butoxy)ditungsten(III) is thus obtained by the salt metathesis reaction from a ditungsten heptachloride: [ 5 ]
Sodium tert -butoxide forms clusters in the solid state, both hexamers [ 6 ] and nonamers. [ 7 ] | https://en.wikipedia.org/wiki/Sodium_tert-butoxide |
Sodium tetrachloroaurate is an inorganic compound with the chemical formula NaAuCl 4 . It is composed of the ions Na + and AuCl 4 − . It exists in the anhydrous and dihydrate states. At room temperature, it exists as a golden-orange solid. The anhydrous and dihydrate forms are available commercially. [ 1 ]
The conventional method of preparation of sodium tetrachloroaurate involves the addition of tetrachloroauric acid solution to sodium chloride or sodium carbonate to form a mixture. The mixture is stirred at 100 °C, and then subjected to evaporation, cooling, crystallization , and drying to obtain the orange crystals of sodium tetrachloroaurate. [ 4 ] [ 6 ]
However, more efficient preparation methods have been discovered recently. These are the addition of gold with sodium oxy-halogen salts and hydrochloric acid. [ 6 ]
It is used in a wide range of applications. For example, it is used as a catalyst for the hydrochlorination of acetylene , or the oxidation of sulfides . [ 4 ] | https://en.wikipedia.org/wiki/Sodium_tetrachloroaurate |
Sodium thiosulfate ( sodium thiosulphate ) is an inorganic compound with the formula Na 2 S 2 O 3 ·(H 2 O) x . Typically it is available as the white or colorless pentahydrate (x = 5), which is a white solid that dissolves well in water. The compound is a reducing agent and a ligand , and these properties underpin its applications. [ 2 ]
Sodium thiosulfate is used predominantly in dyeing . It converts some dyes to their soluble colorless "leuco" forms. It is also used to bleach "wool, cotton, silk, ...soaps, glues, clay, sand, bauxite, and... edible oils, edible fats, and gelatin." [ 2 ]
Sodium thiosulfate is used in the treatment of cyanide poisoning . [ 3 ] It is on the World Health Organization's List of Essential Medicines . [ 4 ] [ 5 ] Other uses include topical treatment of ringworm and tinea versicolor , [ 3 ] [ 6 ] and treating some side effects of hemodialysis [ 7 ] and chemotherapy . [ 8 ] [ 9 ] In September 2022, the U.S. Food and Drug Administration (FDA) approved sodium thiosulfate under the trade name Pedmark to lessen the risk of ototoxicity and hearing loss in infant, child, and adolescent cancer patients receiving the chemotherapy medication cisplatin . [ 10 ] [ 11 ]
In photography, sodium thiosulfate is used in both film and photographic paper processing as a fixer , sometimes still called 'hypo' from the original chemical name, hyposulphite of soda. [ 12 ] It functions to dissolve silver halides , e.g., AgBr , components of photographic emulsions. Ammonium thiosulfate is typically preferred to sodium thiosulfate for this application. [ 2 ]
The ability of thiosulfate to dissolve silver ions is related to its ability to dissolve gold ions.
It is used to dechlorinate tap water including lowering chlorine levels for use in aquariums, swimming pools, and spas (e.g., following superchlorination ) and within water treatment plants to treat settled backwash water prior to release into rivers. [ 2 ] The reduction reaction is analogous to the iodine reduction reaction.
In pH testing of bleach substances, sodium thiosulfate neutralizes the color-removing effects of bleach and allows one to test the pH of bleach solutions with liquid indicators. The relevant reaction is akin to the iodine reaction: thiosulfate reduces the hypochlorite (the active ingredient in bleach ) and in so doing becomes oxidized to sulfate. The complete reaction is:
Similarly, sodium thiosulfate reacts with bromine , removing the free bromine from the solution. Solutions of sodium thiosulfate are commonly used as a precaution in chemistry laboratories when working with bromine and for the safe disposal of bromine, iodine , or other strong oxidizers.
Two polymorphs are known as pentahydrate. The anhydrous salt exists in several polymorphs. [ 2 ] In the solid state, the thiosulfate anion is tetrahedral in shape and is notionally derived by replacing one of the oxygen atoms by a sulfur atom in a sulfate anion. The S-S distance indicates a single bond, implying that the terminal sulfur holds a significant negative charge and the S-O interactions have more double-bond character.
Sodium thiosulfate is prepared by oxidation of sodium sulfite with sulfur . [ 2 ] It is also produced from waste sodium sulfide from the manufacture of sulfur dyes . [ 13 ]
This salt can also be prepared by boiling aqueous sodium hydroxide and sulfur according to the following equation. [ 14 ] [ 15 ] However, this is not recommended outside of a laboratory, as exposure to hydrogen sulfide can result if improperly handled.
Upon heating to 300 °C, it decomposes to sodium sulfate and sodium polysulfide :
Thiosulfate salts characteristically decompose upon treatment with acids. Initial protonation occurs at sulfur. When the protonation is conducted in diethyl ether at −78 °C, H 2 S 2 O 3 ( thiosulfuric acid ) can be obtained. It is a somewhat strong acid with p K a s of 0.6 and 1.7 for the first and second dissociations, respectively. Under normal conditions, acidification of solutions of this salt excess with even dilute acids results in complete decomposition to sulfur , sulfur dioxide , and water : [ 13 ]
Thiosulfate forms complexes with transition metal ions . One such complex is [Au(S 2 O 3 ) 2 ] 3− .
Some analytical procedures exploit the oxidizability of thiosulfate anion by iodine . The reaction produces tetrathionate :
Due to the quantitative nature of this reaction, as well as because Na 2 S 2 O 3 ·5H 2 O has an excellent shelf-life, it is used as a titrant in iodometry . Na 2 S 2 O 3 ·5H 2 O is also a component of iodine clock experiments.
This particular use can be set up to measure the oxygen content of water through a long series of reactions in the Winkler test for dissolved oxygen . It is also used in estimating volumetrically the concentrations of certain compounds in solution ( hydrogen peroxide , for instance) and in estimating the chlorine content in commercial bleaching powder and water.
Alkylation of sodium thiosulfate gives S -alkylthiosulfates, which are called Bunte salts . [ 16 ] The alkylthiosulfates are susceptible to hydrolysis, affording the thiol. This reaction is illustrated by one synthesis of thioglycolic acid :
Sodium thiosulfate has low toxicity. LDLo for rabbits is 4000 mg/kg. [ 2 ] | https://en.wikipedia.org/wiki/Sodium_thiosulfate |
Sodium triacetoxyborohydride , also known as sodium triacetoxyhydroborate , commonly abbreviated STAB , is a chemical compound with the formula Na[(CH 3 COO) 3 BH] . Like other borohydrides , it is used as a reducing agent in organic synthesis . This colourless salt is prepared by protonolysis of sodium borohydride with acetic acid : [ 1 ]
Sodium triacetoxyborohydride is a milder reducing agent than sodium borohydride or even sodium cyanoborohydride . It reduces aldehydes but not most ketones. It is especially suitable for reductive aminations of aldehydes and ketones. [ 2 ] [ 3 ] [ 4 ]
However, unlike sodium cyanoborohydride , sodium triacetoxyborohydride quickly decomposes upon contact with methanol . It reacts only slowly with ethanol and isopropanol and therefore can be used with these solvents. [ 3 ]
NaBH(OAc) 3 may also be used for reductive alkylation of secondary amines with aldehyde- bisulfite adducts. [ 5 ]
The combination of Na[BH 4 ] with carboxylic acids results in the formation of acyloxyborohydride species other than sodium triacetoxyborohydride. These modified species can perform a variety of reductions not normally associated with borohydride chemistry, such as alcohols to hydrocarbons and nitriles to primary amines. [ 6 ] | https://en.wikipedia.org/wiki/Sodium_triacetoxyborohydride |
Sodium triethylborohydride is an organoboron compound with the formula NaBH(C 2 H 5 ) 3 . It is a colorless, pyrophoric solid that is commercially available in toluene solution, unlike the related LiBH(C 2 H 5 ) 3 which is typically sold as a THF solution. [ 1 ] It is commonly used for the reductive activation of homogeneous catalysts , converting metal halides to hydrides. Sodium triethylborohydride has been prepared by treating a hot toluene slurry of sodium hydride with triethylborane . [ 2 ] The trimethylborohydride analogue, which is assumed to be structurally similar to the triethylborohydride, adopts a tetrameric structure in toluene solution. [ 3 ] NaBHEt 3 forms a dimeric adduct with TMEDA . [ 4 ] | https://en.wikipedia.org/wiki/Sodium_triethylborohydride |
Sodium trifluoromethanesulfinate (CF 3 SO 2 Na) is the sodium salt of trifluoromethanesulfinic acid. Together with t-butyl hydroperoxide , an oxidant, this compound was found to be a suitable reagent for introducing trifluoromethyl groups onto electron-rich aromatic compounds by Langlois; this reagent is also known as the Langlois reagent . This reaction operates via a free radical mechanism. [ 1 ]
This reagent is also able to trifluoromethylate electron-deficient aromatic compounds under biphasic conditions. [ 2 ] Zinc difluoromethanesulfinate , a related polymeric coordination complex , is able to introduce difluoromethyl groups (CHF 2 -) onto aromatic compounds under similar biphasic conditions as well. [ 3 ]
With the use of DMSO as an oxidant, it provides an environmentally friendly way for the synthesis of β-trifluoromethyl alcohols from alkenes. [ 4 ] | https://en.wikipedia.org/wiki/Sodium_trifluoromethanesulfinate |
Sodium tris(carbonato)cobalt(III) is the inorganic compound with the formula Na 3 Co(CO 3 ) 3 •3H 2 O. The salt contains an olive-green metastable cobalt(III) coordination complex . The salt, a homoleptic metal carbonato complex , is sometimes referred to as the “Field-Durrant precursor” and is prepared by the “Field-Durrant synthesis”. It is used in the synthesis of other cobalt(III) complexes. Otherwise cobalt(III) complexes are generated from cobalt(II) precursors, a process that requires an oxidant. [ 1 ]
An aqueous solution of cobalt(II) nitrate and hydrogen peroxide is added to a solution of sodium bicarbonate, leading to precipitation of the olive solid. [ 2 ] The method is a modification of the synthesis of what has been described as “Co 2 (CO 3 ) 3 ”. [ 3 ]
The identity of this complex anion is uncertain, suggestions include [Co(κ 2 -CO 3 ) 3 ] 3- , [Co(κ 1 -CO 3 H) 3 (OH) 3 ] 3- , and [Co(κ 2 -CO 3 ) 2 (κ 1 -CO 3 )(OH 2 )] 3- . Thermal gravimetric analysis favors the presence of one aquo ligand, [ 4 ] and infra-red spectroscopy indicates the presence of both bi- and unidentate carbonate ligands. The addition of [Co(NH 3 ) 6 ]Cl 3 to fresh solutions of sodium tris(carbonato)cobalt(III) precipitates anhydrous salt [Co(NH 3 ) 6 ] [Co(κ 2 -CO 3 ) 3 ]. This salt has been characterized by X-ray crystallography , which established that the anionic complex features three bidentate (κ 2 -) carbonate ligands. [ 5 ]
To some extent, the exact description of the title salt is unimportant since it is only used as a synthetic intermediate, it has no intrinsic value. Products include [Co(H 2 O) 6 ] 3+ , [Co(κ 2 -CO 3 )(H 2 O) 4 ] + , and [Co(κ 2 -CO 3 ) 2 (H 2 O) 2 ] − and their derivatives where the aquo ligand has been displaced. [ 5 ] The closely related potassium tris(carbonatocobalt(III) has also been used for the preparation of diverse complexes. These derivatives include [Co(NH 3 ) 2 (κ 2 -CO 3 ) 2 ] − and [Co(CN) 2 (κ 2 -CO 3 ) 2 ] 3- , rare examples of biscarbonato cobalt(III) complexes. Other derivatives include the dinitrite [Co(NH 3 ) 2 (κ 2 -CO 3 )(NO 2 ) 2 ] − and the oxalate [Co(NH 3 ) 2 (κ 2 -CO 3 )(C 2 O 4 )] − . [ 6 ] | https://en.wikipedia.org/wiki/Sodium_tris(carbonato)cobalt(III) |
Sodium tungsten bronze is a form of insertion compound with the formula Na x WO 3 , where x is equal to or less than 1. So named because of its metallic lustre, its electrical properties range from semiconducting to metallic depending on the concentration of sodium ions present; it can also exhibit superconductivity .
Prepared in 1823 by the chemist Friedrich Wöhler , sodium tungsten bronze was the first alkali metal bronze to be discovered. [ 1 ] Tungsten bronzes owe some of their properties to the relative stability of the tungsten(V) cation that is formed. [ 2 ] A similar family of molybdenum bronzes may have been discovered in 1885 by Alfred Stavenhagen and E. Engels, [ 3 ] but they are formed in a very narrow range of temperatures and were not reported again until the 1960s. [ 4 ]
Sodium tungsten bronze, like other tungsten bronzes, is resistant to chemical reaction under both acidic and basic conditions. Colour is dependent upon the proportion of sodium in the compound, ranging from golden at x ≈ 0.9, through red, orange and deep purple, to blue-black when x ≈ 0.3.
The electrical resistivity of the bronze depends on the proportion of sodium in the compound, with specific resistances of 1.66 mΩ being measured for some samples. [ 5 ] It has been suggested that electrons, released when the sodium atoms are ionised, are conducted readily through the tungsten t 2g and oxygen π orbitals. [ 2 ] This can be observed in the XPS [ 6 ] and UPS [ 7 ] spectra: the peak representing the tungsten 5 d band becomes more intense as x rises.
For values of x below 0.3, the bronze is semiconducting rather than metallic. [ 2 ] When cooled sufficiently, sodium tungsten bronze becomes a superconductor , with the critical temperature ( T c ) for Na 0.23 WO 3 being approximately 2.2 kelvin . [ 8 ] The first record of superconductivity in a tungsten bronze was in 1964, with a T c of 0.57 K. [ 9 ]
When x = 1, sodium tungsten bronze adopts a cubic phase: the perovskite crystal structure. [ 10 ] In this form, the structure consists of corner-sharing WO 6 octahedra with sodium ions in the interstitial gaps. For x values between 0.9 and 0.3, the structure remains similar but with an increasing deficiency of sodium ions and a smaller lattice parameter. [ 10 ]
A number of other structure types can also be adopted, with varying electrical properties: cubic, tetragonal I and hexagonal phases are metallic, whereas orthorhombic and tetragonal II structures are semiconducting. [ 11 ]
Wöhler's 1823 synthesis involved reducing sodium tungstate and tungsten trioxide with hydrogen gas at red heat. A more modern approach reduces a melt of the reactants with electricity rather than with hydrogen. [ 12 ] Microwave synthesis is also possible, [ 13 ] using tungsten powder as the reducing agent. Hydrothermal (both batch and flow) syntheses are also possible. [ 14 ]
The sodium in this compound can be replaced by other alkali metals to form their tungsten bronzes, and by other metals such as tin and lead. [ 15 ] Molybdenum bronzes also exist but are less stable than their tungsten counterparts. [ 2 ] | https://en.wikipedia.org/wiki/Sodium_tungsten_bronze |
Sodium–potassium alloy , colloquially called NaK (commonly pronounced / n æ k / ), [ 2 ] is an alloy of the alkali metals sodium (Na, atomic number 11) and potassium (K, atomic number 19) that is normally liquid at room temperature. [ 3 ] Various commercial grades are available. NaK is highly reactive with water (like its constituent elements) and may catch fire when exposed to air , so must be handled with special precautions.
NaK containing 40% to 90% potassium by mass is liquid at room temperature . The eutectic mixture consists of 77% potassium and 23% sodium by mass (NaK-77), and it is a liquid from −12.6 to 785 °C (9.3 to 1,445.0 °F), and has a density of 0.866 g/cm 3 at 21 °C (70 °F) and 0.855 g/cm 3 at 100 °C (212 °F), making it less dense than water. [ 3 ] It is highly reactive with water and is stored usually under hexane or other hydrocarbons, or under an inert gas (usually dry nitrogen or argon [ 5 ] ) if high purity and low levels of oxidation are required.
A solid compound, Na 2 K , exists at low temperatures, containing 46 percent potassium by mass.
NaK has a very high surface tension , which makes large amounts of it pull into a bun -like shape. Its specific heat capacity is 982 J/(kg⋅K), which is roughly one quarter of that for water, but heat transfer is higher over a temperature gradient due to higher thermal conductivity. [ 6 ]
When stored in air , it forms a yellow potassium superoxide coating and may ignite. This superoxide reacts explosively with water and organics. NaK is not dense enough to sink in most hydrocarbons , but will sink in lighter mineral oil . It is unsafe to store in this manner if the superoxide has formed. A large explosion took place at the Oak Ridge Y-12 facility on December 8, 1999 , when NaK cleaned up after an accidental spill and inappropriately treated with mineral oil was scratched with a metal tool. [ 7 ] The liquid alloy also attacks PTFE ("Teflon"). [ 8 ] Sodium–potassium alloy polymerizes dimethyldichlorosilane into polysilanes with a Si-Si backbone and methyl radicals, primarily dodecamethylcyclohexasilane . [ 9 ] 6 ( CH 3 ) 2 SiCl 2 + 12 M ⟶ [ ( CH 3 ) 2 Si ] 6 + 12 MCl ( M = Na , K ) {\displaystyle {\ce {6 (CH3)2SiCl2 + 12 M -> [(CH3)2Si]6 + 12 MCl}}\ {\ce {(M = Na, K)}}}
Further alloys with low melting points are Cs 77 K 23 at −37.5 °C (−35.5 °F), Cs 19 Na at −30 °C (−22 °F) and Na 2 Rb 23 at −5 °C (23 °F). The alloy consisting of 40.8 % caesium, 11.8 % sodium and 47.4 % potassium has a melting point of −79.4 °C (−110.9 °F). [ clarification needed ]
NaK has been used as the coolant in experimental fast neutron nuclear reactors . Unlike commercial plants, these are frequently shut down and defuelled. Use of lead or pure sodium, the other materials used in practical reactors, would require continual heating to maintain the coolant as a liquid. Use of NaK overcomes this. The Dounreay Fast Reactor is an example.
The first nuclear reactor in space, [ 10 ] [ 11 ] the United States' experimental SNAP-10A satellite, used NaK as coolant. The NaK was circulated through the core and thermoelectric converters by a liquid metal direct current conduction-type pump. [ 12 ] The satellite was launched in 1965, [ 13 ] and as of 2022 is the only fission reactor power system launched into space by the United States. [ 14 ]
The Soviet RORSAT radar satellites were powered by a BES-5 reactor, which was cooled with NaK. [ 15 ] [ 16 ] In addition to the wide liquid temperature range, NaK has a very low vapor pressure , which is important in the vacuum of space .
An unintended consequence of the usage as a coolant on orbiting satellites has been the creation of additional space debris . NaK coolant has leaked from a number of satellites, including Kosmos 1818 and Kosmos 1867 . The coolant self-forms into droplets of sodium–potassium of up to several centimeters in size. [ 17 ] These objects are space debris. [ 18 ]
The Danamics LMX Superleggera CPU cooler uses NaK to transport heat from the CPU to its cooling fins. [ 19 ]
In contact with water, hydrogen is created. [ 20 ] Hence, sodium–potassium alloys are used as desiccants in drying solvents prior to distillation .
Eutectic NaK (NaK-77, an alloy of 77% potassium and 23% sodium by mass) can be used as a hydraulic fluid in high-temperature and high-radiation environments, for temperature ranges of −12 to 760 °C (10 to 1,400 °F). Its bulk modulus at 538 °C (1,000 °F) is 2.14 GPa, higher than of a hydraulic oil at room temperature. Its lubricity is poor, so positive-displacement pumps are unsuitable and centrifugal pumps have to be used. Addition of caesium shifts the useful temperature range to −71 to 704 °C (−96 to 1,299 °F). NaK-77 was tested in hydraulic and fluidic systems for the Supersonic Low Altitude Missile . [ 21 ] NaK may also be used to transmit forces inside high temperature pressure transducers as an alternative to mercury . [ 22 ]
NaK can be used as catalyst in some reactions, such as isobutylbenzene , a precursor to ibuprofen . [ 23 ]
Industrially, NaK is produced in a reactive distillation . [ 24 ] | https://en.wikipedia.org/wiki/Sodium–potassium_alloy |
The Alexander von Humboldt Foundation of Germany bestowed the Sofia Kovalevskaya Award from 2002 to 2020. Sofia Kovalevskaya (1850–1891) was the first major Russian female mathematician , who made important contributions to mathematical analysis , differential equations and mechanics , and the first woman appointed to a full professorship in Northern Europe . This prestigious award named in her honor was given to promising young academics to pursue their line of research in the sciences or arts and humanities. The foundation encouraged applications from all areas of the academy so long as the investigator had received a Ph.D. in the previous six years and could be categorized as "top flight" by their publications and experience as commensurate with age. [ 1 ] [ 2 ]
There have been a total 139 awardees since the inception of the Sofia Kovalevskaya Award in 2002 until its closure in 2020. [ 3 ] Individual awards totalled up to 1.6 million Euro each. Funds were awarded to build and lead a team of researchers for a five-year period within a German host institution. [ 4 ] | https://en.wikipedia.org/wiki/Sofia_Kovalevskaya_Award |
Sofituzumab vedotin ( INN ; [ 1 ] development code DMUC5754A ) is a monoclonal antibody designed for the treatment of ovarian cancer . [ 2 ]
This drug was developed by Genentech / Roche .
Sofituzumab vedotin is an antibody-drug conjugate that targets MUC16, a protein that is overexpressed in several types of cancer including ovarian and pancreatic cancer. The conjugate consists of a human anti-nectin-4 antibody linked to the cytotoxic agent MMAE, which is released after internalization by the cancer cell. In addition to its direct cytotoxic effect, sofituzumab vedotin may also mediate antitumor activity through signal transduction inhibition, antibody-dependent cellular cytotoxicity, and complement-dependent cytotoxicity. Clinical trials have shown promising results in the treatment of ovarian and pancreatic cancer. [ 3 ]
This monoclonal antibody –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sofituzumab_vedotin |
Sofosbuvir , sold under the brand name Sovaldi among others, is a medication used to treat hepatitis C . [ 3 ] It is taken by mouth . [ 3 ] [ 5 ]
Common side effects include fatigue, headache, nausea, and trouble sleeping. [ 3 ] Side effects are generally more common in interferon-containing regimens. [ 6 ] : 7 Sofosbuvir may reactivate hepatitis B in those who have been previously infected. [ 8 ] In combination with ledipasvir , daclatasvir or simeprevir , it is not recommended with amiodarone due to the risk of an abnormally slow heartbeat . [ 6 ] Sofosbuvir is in the nucleotide analog family of medications and works by blocking the hepatitis C NS5B protein. [ 5 ]
Sofosbuvir was discovered in 2007 and approved for medical use in the United States in 2013. [ 6 ] [ 9 ] [ 10 ] It is on the World Health Organization's List of Essential Medicines . [ 11 ] [ 12 ]
In 2016, the American Association for the Study of Liver Diseases and the Infectious Diseases Society of America jointly published a recommendation for the management of hepatitis C. In this recommendation, sofosbuvir used in combination with other drugs is part of all first-line treatments for HCV genotypes 1, 2, 3, 4, 5, and 6, and is also part of some second-line treatments. [ 13 ] Sofosbuvir in combination with velpatasvir is recommended for all genotypes with a cure rate greater than 90%, and close to 100% in most cases. The duration of treatment is typically 12 weeks. [ 13 ] [ 14 ]
Sofosbuvir is also used with other medications and longer treatment durations, depending on specific circumstances, genotype and cost-effectiveness–based perspective. For example, for the treatment of genotypes 1, 4, 5, and 6 hepatitis C infections, sofosbuvir can be used in combination with the viral NS5A inhibitor ledipasvir . [ 15 ] In genotype 2 and 3 HCV infections, sofosbuvir can be used in combination with daclatasvir . For the treatment of cases with cirrhosis or liver transplant patients, weight-based ribavirin is sometimes added. Peginterferon with or without sofosbuvir is not recommended in an initial HCV treatment. [ 13 ]
Compared to previous treatments, sofosbuvir-based regimens provide a higher cure rate, fewer side effects, and a two- to four-fold reduction in therapy duration. [ 16 ] [ 17 ] [ 18 ] Sofosbuvir allows most people to be treated successfully without the use of peginterferon, an injectable drug with severe side effects that is a key component of older drug combinations for the treatment of hepatitis C virus. [ 19 ] [ 20 ]
For people who have experienced treatment failure with some form of combination therapy for hepatitis C infection, one of the next possible steps would be retreatment with sofosbuvir and either ledipasvir or daclatasvir, with or without weight-based ribavirin. The genotype and particular combination therapy a person was on when the initial treatment failed are also taken into consideration when deciding which combination to use next. The duration of retreatment can range from 12 weeks to 24 weeks depending on several factors, including which medications are used for the retreatment, whether the person has liver cirrhosis or not, and whether the liver damage is classified as compensated cirrhosis or decompensated cirrhosis . [ 13 ]
No adequate human data are available to establish whether or not sofosbuvir poses a risk to pregnancy outcomes. [ 6 ] However, ribavirin , a medication that is often given together with sofosbuvir to treat hepatitis C, is assigned a Pregnancy Category X (contraindicated in pregnancy) by the FDA. [ 21 ] Pregnant women with hepatitis C who take ribavirin have shown some cases of birth defects and death in their fetus. [ 22 ] It is recommended that sofosbuvir/ribarivin combinations be avoided in pregnant females and their male sexual partners in order to reduce harmful fetal defects caused by ribavirin. Females who could potentially become pregnant should undergo a pregnancy test 2 months prior to starting the sofosbuvir/ribavirin/peginterferon combination treatment, monthly throughout the duration of the treatment, and six months post-treatment to reduce the risk of fetal harm in case of accidental pregnancy. [ 22 ]
It is unknown whether sofosbuvir and ribavirin pass into breastmilk; therefore, it is recommended that the mother does not breastfeed during treatment with sofosbuvir alone or in combination with ribavirin. [ 6 ] [ 22 ]
There are no specific contraindications for sofosbuvir when used alone. However, when used in combination with ribavirin or peginterferon alfa/ribavirin, or others, the contraindications applicable to these agents are applied. [ 6 ]
Sofosbuvir used alone and in combination with other drugs such as ribavirin with or without a peginterferon has a good safety profile. Common side effects are fatigue, headache, nausea, rash, irritability, dizziness, back pain, and anemia. Most side effects are more common in interferon-containing regimens as compared to interferon-free regimens. For example, fatigue and headache are nearly reduced by half, influenza-like symptoms are reduced to 3–6% as compared to 16–18%, and neutropenia is almost absent in interferon-free treatment. [ 6 ] : 7 [ 23 ]
Sofosbuvir may reactivate hepatitis B in those who have been previously infected. [ 8 ] The European Medicines Agency (EMA) has recommended screening all people for hepatitis B before starting sofosbuvir for hepatitis C in order to minimize the risk of hepatitis B reactivation. [ 24 ]
Sofosbuvir (in combination with ledipasvir , daclatasvir or simeprevir ) should not be used with amiodarone due to the risk of abnormally slow heartbeats . [ 6 ]
Sofosbuvir is a substrate of P-glycoprotein , a transporter protein that pumps drugs and other substances from intestinal epithelium cells back into the gut. Therefore, inducers of intestinal P-glycoprotein, such as rifampicin and St. John's wort , could reduce the absorption of sofosbuvir. [ 6 ]
In addition, coadministration of sofosbuvir with anticonvulsants ( carbamazepine , phenytoin, phenobarbital, oxcarbazepine), antimycobacterials ( rifampin , rifabutin, rifapentine), and the HIV protease inhibitor tipranavir and ritonavir is expected to decrease sofosbuvir concentration. Thus, coadministration is not recommended. [ 6 ]
The interaction between sofosbuvir and a number of other drugs, such as ciclosporin , darunavir / ritonavir , efavirenz , emtricitabine , methadone , raltegravir , rilpivirine , tacrolimus , or tenofovir disoproxil , were evaluated in clinical trials and no dose adjustment is needed for any of these drugs. [ 6 ] [ 25 ]
Sofosbuvir inhibits the hepatitis C NS5B protein. [ 5 ] Sofosbuvir appears to have a high barrier to the development of resistance. [ 26 ]
Sofosbuvir is a prodrug of the Protide type, whereby the active phosphorylated nucleotide is granted cell permeability and oral bioavailability. It is metabolized to the active antiviral agent GS-461203 (2'-deoxy-2'-α-fluoro-β- C -methyluridine-5'-triphosphate). GS-461203 serves as a defective substrate for the NS5B protein, which is the viral RNA polymerase, thus acts as an inhibitor of viral RNA synthesis. [ 27 ] Although sofosbuvir has a 3' hydroxyl group to act as a nucleophile for an incoming NTP, a similar nucleotide analogue, 2'-deoxy-2'-α-fluoro-β-C-methylcytidine, is proposed to act as a chain terminator because the 2' methyl group of the nucleotide analogue causes a steric clash with an incoming NTP. [ 28 ] Sofosbuvir may act in a similar way. [ citation needed ]
Sofosbuvir is only administered orally. The peak concentration after oral administration is 0.5–2 hours post-dose, regardless of initial dose. [ 29 ] Peak plasma concentration of the main circulating metabolite GS-331077 occurs 2–4 hours post-dose. [ 29 ] GS-331077 is the pharmacologically inactive nucleoside . [ 6 ]
Plasma protein binding of sofosbuvir is 61–65%, while GS-331077 has minimal binding. [ 6 ]
Sofosbuvir is activated in the liver to the triphosphate GS-461203 by hydrolysis of the carboxylate ester by either of the enzymes cathepsin A or carboxylesterase 1 , followed by cleaving of the phosphoramidate by the enzyme histidine triad nucleotide-binding protein 1 (HINT1), and subsequent repeated phosphorylation . [ 30 ] Dephosphorylation creates the inactive metabolite GS-331077. The half life of sofosbuvir is 0.4 hours, and the half life of GS-331077 is 27 hours. [ 6 ] Following a single 400 mg oral dose of sofosbuvir, 80% is excreted in urine, 14% in feces, and 2.5% in expired air recovery. However, of the urine recovery 78% was the metabolite (GS-331077) and 3.5% was sofosbuvir. [ 29 ]
Prior to the discovery of sofosbuvir, a variety of nucleoside analogs had been examined as antihepatitis C treatments, but these exhibited relatively low potency. This low potency arose in part because the enzymatic addition of the first of the three phosphate groups of the triphosphate is slow. The design of sofosbuvir, based on the ProTide approach, avoids this slow step by building the first phosphate group into the structure of the drug during synthesis. Additional groups are attached to the phosphorus to temporarily mask the two negative charges of the phosphate group, thereby facilitating entry of the drug into the infected cell. [ 31 ] The NS5B protein is a RNA-dependent RNA polymerase critical for the viral reproduction cycle. [ citation needed ]
Sofosbuvir was discovered in 2007 by Michael J. Sofia , a scientist at Pharmasset , and the drug was first tested in people in 2010. In 2011, Gilead Sciences bought Pharmasset for about $11 billion. [ 10 ] Gilead submitted the New Drug Application for sofosbuvir in combination with ribavirin in April 2013, and in October 2013 it received the FDA's Breakthrough Therapy Designation . [ 32 ] In December 2013, the FDA approved sofosbuvir in combination with ribavirin for oral dual therapy of HCV genotypes 2 and 3, and for triple therapy with injected pegylated interferon (pegIFN) and RBV for treatment-naive people with HCV genotypes 1 and 4. [ 33 ] [ 34 ] Two months before, the FDA had approved another drug, simeprevir , as a hepatitis C treatment. [ 33 ]
In 2014, the fixed dose combination drug sofosbuvir/ ledipasvir , the latter a viral NS5A inhibitor, was approved; it had also been granted breakthrough status. [ 35 ]
Prior to the availability of sofosbuvir, hepatitis C treatments involved 6 to 12 months of treatment with an interferon-based regimen. This regimen provided cure rates of 70% or less and was associated with severe side effects, including anemia, depression, severe rash, nausea, diarrhea, and fatigue. As sofosbuvir clinical development progressed, physicians began to "warehouse" people in anticipation of its availability. [ 36 ] Sofosbuvir's U.S. launch was the fastest of any new drug in history. [ 37 ]
Sofosbuvir is on the World Health Organization's List of Essential Medicines . [ 11 ] [ 12 ]
Following its approval by the FDA in 2013, [ 33 ] the price of sofosbuvir as quoted in various media sources in 2014 ranged from $84,000 to $168,000 depending on course of treatment in the U.S. [ 38 ] and £35,000 in the United Kingdom for a 12-week regimine, [ 39 ] causing considerable controversy. [ 40 ] [ 41 ] Sofosbuvir was more affordable in Japan and South Korea at approximately $300 and $5900 respectively for a 12-week treatment, with each government covering 99% and 70% of the cost respectively. [ 42 ] [ 43 ] In 2014, Gilead announced it would work with generic manufacturers in 91 developing countries to produce and sell sofosbuvir, and that it would sell a name brand version of the product in India for approximately $300 per course of treatment; it had signed agreements with generic manufacturers by September 2015. [ 44 ] [ 45 ]
Since its launch, the price of sofosbuvir declined as more competitors entered the direct-acting antiviral (DAA) market. [ 46 ] In 2020, the price for a course of sofosbuvir was $64,693 in the United States. [ 47 ] In 2014, the list price of a 12-week combination treatment with a sofosbuvir-based regimen ranged from US$ 84,000 to $94,000. [ 48 ] [ 49 ] [ 50 ] In April 2014, U.S. House Democrats Henry Waxman, Frank Pallone Jr., and Diana DeGette wrote Gilead Sciences Inc. questioning the $84,000 price for sofosbuvir. They specifically asked Gilead CEO John Martin to "explain how the drug was priced, what discounts are being made available to low-income patients and government health programs, and the potential impact to public health by insurers blocking or delaying access to the medicine because of its cost." [ 51 ] Sofosbuvir is cited as an example of how specialty drugs present both benefits and challenges. [ 51 ] [ 52 ] [ 53 ]
Sofosbuvir also is an excellent example of both the benefit and the challenge of specialty medications. On one hand, this agent offers up to a 95% response rate as part of an interferon-free treatment regimen for hepatitis C. Generally speaking, it is more effective and better tolerated than alternative treatments. Unfortunately, the current per pill cost—$1,000—results in an $84,000 treatment course, creating barriers to therapy for many. Patients, providers, and payors alike have expressed outrage, and the debate has even drawn the attention of the US Congress. Despite these concerns, sofosbuvir rapidly has become a top seller in the United States... [ 52 ]
In February 2015, Gilead announced that due in part to negotiated discounts with pharmacy benefit managers and legally mandated discounts to government payers, the average discount-to-list price in 2014 was 22%. The company estimated that the average discount in 2015 would be 46%. [ 54 ] According to the California Technology Assessment Forum, a panel of academic pharmacoeconomic experts, representatives of managed care organizations, and advocates for people with hepatitis, a 46% discount would bring the average price of treatment to about $40,000, at which price sofosbuvir-based treatment regimens represent a "high value" for people and healthcare systems. [ 55 ] [ 56 ] [ 57 ]
Because of sofosbuvir's high price in the United States, by 2017, some states—such as Louisiana—were withholding the medicine from Medicaid patients with hepatitis until their livers were severely damaged. [ 58 ] This puts "patients at increased risk of medical complications" and contributes to the "transmission of the hepatitis C virus". [ 59 ] In an article published in May 2016 in Health Affairs , the authors proposed the invocation of the federal " government patent use " law which would enable the government to procure "important patent-protected" drugs at lower prices while compensating "the patent-holding companies reasonable royalties ... for research and development." [ 59 ] By July 2017, Louisiana's health secretary Rebekah Gee, who described Louisiana as America's "public-health-crisis cradle", was investigating the use of the "government patent use" as a strategy. [ 58 ]
Unlike other comparable Western developed countries , sofosbuvir is far more affordable in Japan and South Korea at approximately $300 and $2165 cost to patients respectively for a 12-week treatment, as each government covers 99% and 70% of the original cost respectively. [ 42 ] [ 43 ] [ 60 ]
In Germany, negotiations between Gilead and health insurers led to a price of €41,000 for 12 weeks of treatment. This is the same price previously negotiated with the national healthcare system in France, except that additional discounts and rebates apply in France depending on the volume of sales and the number of treatment failures. [ 61 ]
In Switzerland, the price is fixed by the government every three years. The price in 2016 was CHF 16,102.50 (about 1:1 to the US dollar) for 24 pills of 400 mg. [ 62 ]
In 2020, the originator price per course of sofosbuvir was £ 35,443. [ 47 ] In 2013, the price in the United Kingdom was expected to be £ 35,000 for a 12-weeks course. [ 39 ] NHS England established 22 Operational Delivery Networks to roll out delivery, which was approved by the National Institute for Health and Care Excellence in 2015, and proposes to fund 10,000 courses of treatment in 2016–17. Each was given a "run rate" of how many people they were allowed to treat, and this was the NHS's single biggest new treatment investment in 2016. [ 63 ]
As of 2015, sofosbuvir is included on the list of essential medications in Croatia and its cost is fully covered by the Croatian Health Insurance Fund . As a result of negotiations with the manufacturer, only therapies with successful outcome would be paid by the Fund with the rest being covered by the manufacturer. [ 64 ]
In July 2014, Gilead Sciences filed a patent for sofosbuvir in India. If the office of the controller general of patents had granted it, Gilead would have obtained exclusive rights to produce and sell sofosbuvir in the country. However, in January 2015, the Indian Patent Office rejected Gilead's application. Gilead's lawyers moved the Delhi High Court against this decision. That decision was overturned on appeal in February 2015. [ 65 ] [ 66 ] In the meantime, it [ clarification needed ] granted Indian companies voluntary licenses (VLs), which allowed them to make and sell in a selected few countries at a discounted price. This agreement also granted 7% of the royalties to Gilead. However, the list of countries open to Indian firms under this agreement excluded 73 million people with hepatitis C. [ 67 ]
In 2014, Gilead announced it would seek generic licensing agreements with manufacturers to produce sofosbuvir in 91 developing countries, which contained 54% of the world's HCV-infected population. Gilead also said it would sell a name brand version of the product in India for $300 per course of treatment, approximately double a third party estimate of the minimum achievable cost of manufacture. [ 44 ] It had signed licenses with generic manufacturers by September 2015. [ 45 ] The leader of one Indian activist group called this move inadequate, [ 45 ] but nine companies launched products, which "unleashed a fierce marketing war", according to India's The Economic Times . [ 1 ]
In Egypt, which had the world's highest incidence of hepatitis C, Gilead offered sofosbuvir at the discounted price of $900 to the Egyptian government. The government in turn made it free to patients. Later, Gilead licensed a generic version to be available in Egypt. [ 68 ]
The Access to Medicine Index ranked Gilead first among the world's 20 largest pharmaceutical countries in the Pricing, Manufacturing and Distribution category in both 2013 and 2014, citing Gilead's "leading performance in equitable pricing." [ 69 ] In contrast, Jennifer Cohn of Doctors Without Borders and the organization Doctors of the World criticized the price of sofosbuvir as reflecting "corporate greed" and ignoring the needs of people in developing countries. [ 40 ] [ 41 ]
In Algeria , as of 2011 about 70,000 people were infected with hepatitis C. [ 70 ] As of August 2015, Gilead had licensed its partners in India to sell sofosbuvir in Algeria. [ 71 ] [ 72 ] It had been criticized for not making the drug available in middle-income countries including Algeria prior to that. [ 70 ] [ 71 ] [ 73 ]
The price has generated considerable controversy. [ 40 ] [ 41 ] In 2017, the range of costs per treatment varied from about $84,000 [ 74 ] to about $50. [ 75 ]
In February 2015, it was reported [ 76 ] that Doctors of the World had submitted an objection to Gilead's patent [ 77 ] at the European Patent Office , claiming that the structure of sofosbuvir is based on already known molecules. [ 78 ] In particular, Doctors of the World argued that the Protide technology powering sofosbuvir was previously invented by the Chris McGuigan team at Cardiff University in the UK, and that the Gilead drug is not therefore inventive. [ 79 ] [ 80 ] The group filed challenges in other developing countries as well. [ 81 ] These challenges were unsuccessful. [ 82 ]
Due to the high cost of sofosbuvir in the U.S., as of 2016 increasing numbers of Americans with hepatitis C were traveling to India to purchase the drug. Similarly, increasing numbers of Chinese were also traveling to India to purchase sofosbuvir, which had not yet been approved for sale in China by the country's State Food and Drug Administration (SFDA). [ 83 ]
Combinations of sofosbuvir with NS5A inhibitors, such as daclatasvir , ledipasvir or velpatasvir , have shown sustained virological response rates of up to 100% in people infected with HCV. Most studies indicate that the efficacy rate is between 94% and 97%; much higher than previous treatment options. [ 84 ] [ 85 ] [ 86 ] That treatments could be conducted at very low costs was demonstrated by Hill and coworkers who presented data on 1,160 patients who used generic versions of solfosbuvir, ledipasvir, plus daclatasvir from suppliers in India, Egypt, China and other countries and reported over 90% success at costs of about $50 per therapy. [ 75 ]
Sofosbuvir has also been tested against other viruses such as the Zika virus [ 87 ] and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). [ 88 ]
At DEF CON 32, Mixæl Swan Laufer , a representative of the Four Thieves Vinegar Collective , presented a talk titled "Eradicating Hepatitis C with BioTerrorism." The presentation argued that advancements in open-source tools and chemistry enable individuals to synthesize certain medications, such as Sovaldi, at home, potentially bypassing high pharmaceutical costs.
During the talk, Laufer demonstrated tools and techniques used by the collective to synthesize pharmaceuticals, showcasing examples of the medications created. To illustrate the efficacy and accessibility of the process, he consumed a dose of Sovaldi onstage, despite not having Hepatitis C, as a symbolic gesture of the drug's claimed safety. [ 89 ] [ 90 ] | https://en.wikipedia.org/wiki/Sofosbuvir |
Soft-bodied organisms are organisms that lack rigid physical skeletons or frame , roughly corresponds to the group Vermes as proposed by Carl von Linné . The term typically refers to non- panarthropod invertebrates from the kingdom Animalia , although many non-vascular plants ( mosses and algae ), fungi (such as jelly fungus ), lichens and slime molds can also be seen as soft-bodied organisms by definition.
All animals have a muscular system of some sort but, since myocytes are tensile actuator units that can only contract and pull but never push, some animals evolved rigid body parts upon which the muscles can attach and act as levers / cantilevers to redirect force and produce locomotive propulsion . These rigid parts also serve as structural elements to resist gravity and ambient pressure , as well as sometimes provide protective surfaces shielding internal structures from trauma and exposure to external thermal, chemical and pathogenic insults. Such physical structures are the commonly referred "skeletons", [ 1 ] which may be internal (as in vertebrates , echinoderms and sponges ) or external (as in arthropods and non- coleoid molluscs ). However, many soft-bodied animals do still have a functional skeleton maintained by body fluid hydrostatics known as a hydroskeleton , [ 2 ] such as that of earthworms , jellyfish , tapeworms , squids and an enormous variety of invertebrates from almost every phyla of the animal kingdom; and many have hardened teeth that allow them to chew , bite and burrow despite the rest of body being soft.
Most soft-bodied animals are small, but they do make up the majority of the animal biomass . If we were to weigh up all animals on Earth with hard parts against soft-bodied ones, estimates indicate that the biomass of soft-bodied animals would be at least twice that of animals with hard parts, quite possibly much larger. [ 3 ] [ dead link ] Particularly the roundworms are extremely numerous. The nematodologist Nathan Cobb described the ubiquitous presence of nematodes on Earth as follows:
"In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites." [ 4 ]
Being a morphological grouping rather than a true phylogenetic group, soft-bodied organisms vary enormously in anatomy. Cnidarians and flatworms have a single opening to the gut and a diffuse nerve system . The roundworms , annelids , molluscs , the various lophoporate phyla and non-vertebrate chordates have a tubular gut open at both ends. While the majority of the soft-bodied animals typically don't have any kind of skeleton, some do, mainly in the form of stiff cuticles (roundworms, water bears ) or hydrostatic skeletons (annelids). [ 5 ]
While lack of a skeleton typically restricts the body size of soft-bodied animals on land, marine representatives can grow to very large sizes. The heaviest soft-bodied organisms are likely the giant squids , with maximum weight estimated at 275 kilograms (606 lb) for females, while arctic lion's mane jellyfish may reach comparable sizes. [ 6 ] [ 7 ] The longest animal on record is also thought to be a soft-bodied organism, a 55 metres (180 ft) long thread-like bootlace worm , Lineus longissimus found on a Scottish beach 1864. [ 8 ] Siphonophores may grow to considerable sizes too, though they are colonial organisms , and each single animal is small. [ 9 ] Most soft-bodied organisms are as small or smaller, even microscopic. The various organisms grouped as mesozoans and the curious Placozoa are typically composed of just a few hundred cells . [ 2 ]
The lack of hard parts in soft-bodied organisms makes them extremely rare in the fossil record . Accordingly, the evolutionary histories of many of the soft-bodied groups are poorly known. The first major find of fossil soft-bodied animals was from the Burgess Shale in Canada . [ 11 ] Today, several sites with Burgess Shale type preservation are known, but the history of many groups of soft-bodied animals is still poorly understood. | https://en.wikipedia.org/wiki/Soft-bodied_organism |
Soft-body dynamics is a field of computer graphics that focuses on visually realistic physical simulations of the motion and properties of deformable objects (or soft bodies ). [ 1 ] The applications are mostly in video games and films. Unlike in simulation of rigid bodies , the shape of soft bodies can change, meaning that the relative distance of two points on the object is not fixed. While the relative distances of points are not fixed, the body is expected to retain its shape to some degree (unlike a fluid ). The scope of soft body dynamics is quite broad, including simulation of soft organic materials such as muscle, fat, hair and vegetation, as well as other deformable materials such as clothing and fabric. Generally, these methods only provide visually plausible emulations rather than accurate scientific/engineering simulations, though there is some crossover with scientific methods, particularly in the case of finite element simulations. Several physics engines currently provide software for soft-body simulation. [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The simulation of volumetric solid soft bodies [ 8 ] can be realised by using a variety of approaches.
In this approach, the body is modeled as a set of point masses (nodes) connected by ideal weightless elastic springs obeying some variant of Hooke's law . The nodes may either derive from the edges of a two-dimensional polygonal mesh representation of the surface of the object, or from a three-dimensional network of nodes and edges modeling the internal structure of the object (or even a one-dimensional system of links, if for example a rope or hair strand is being simulated). Additional springs between nodes can be added, or the force law of the springs modified, to achieve desired effects. Applying Newton's second law to the point masses including the forces applied by the springs and any external forces (due to contact, gravity, air resistance, wind, and so on) gives a system of differential equations for the motion of the nodes, which is solved by standard numerical schemes for solving ODEs . [ 9 ] Rendering of a three-dimensional mass-spring lattice is often done using free-form deformation , [ 10 ] in which the rendered mesh is embedded in the lattice and distorted to conform to the shape of the lattice as it evolves. Assuming all point masses equal to zero one can obtain the Stretched grid method aimed at several engineering problems solution relative to the elastic grid behavior. These are sometimes known as mass-spring-damper models . In pressurized soft bodies [ 11 ] spring-mass model is combined with a pressure force based on the ideal gas law .
This is a more physically accurate approach, which uses the widely used finite element method to solve the partial differential equations which govern the dynamics of an elastic material . The body is modeled as a three-dimensional elastic continuum by breaking it into a large number of solid elements which fit together, and solving for the stresses and strains in each element using a model of the material. [ 12 ] The elements are typically tetrahedral, the nodes being the vertices of the tetrahedra (relatively simple methods exist [ 13 ] [ 14 ] to tetrahedralize a three dimensional region bounded by a polygon mesh into tetrahedra , similarly to how a two-dimensional polygon may be triangulated into triangles). The strain (which measures the local deformation of the points of the material from their rest state) is quantified by the strain tensor ϵ {\displaystyle {\boldsymbol {\epsilon }}} . The stress (which measures the local forces per-unit area in all directions acting on the material) is quantified by the Cauchy stress tensor σ {\displaystyle {\boldsymbol {\sigma }}} . Given the current local strain, the local stress can be computed via the generalized form of Hooke's law : σ = C ε {\displaystyle {\boldsymbol {\sigma }}={\mathsf {C}}{\boldsymbol {\varepsilon }}\,} where C {\displaystyle {\mathsf {C}}} is the elasticity tensor , which encodes the material properties (parametrized in linear elasticity for an isotropic material by the Poisson ratio and Young's modulus ).
The equation of motion of the element nodes is obtained by integrating the stress field over each element and relating this, via Newton's second law , to the node accelerations.
Pixelux (developers of the Digital Molecular Matter system) use a finite-element-based approach for their soft bodies, using a tetrahedral mesh and converting the stress tensor directly into node forces. [ 15 ] Rendering is done via a form of free-form deformation . [ 10 ]
This approach is motivated by variational principles and the physics of surfaces, which dictate that a constrained surface will
assume the shape which minimizes the total energy of deformation (analogous to a soap bubble ). Expressing the energy of a surface in terms of its local deformation (the energy is due to a combination of stretching and bending), the local force on the surface is given by differentiating the energy with respect to position, yielding an equation of motion which can be solved in the standard ways. [ 16 ] [ 17 ]
In this scheme, penalty forces or constraints are applied to the model to drive it towards its original shape [ 18 ] (i.e. the material behaves as if it has shape memory ). To conserve momentum the rotation of the body must be estimated properly, for example via polar decomposition . To approximate finite element simulation, shape matching can be applied to three dimensional lattices and multiple shape matching constraints blended. [ 19 ]
Deformation can also be handled by a traditional rigid-body physics engine , modeling the soft-body motion using a network of multiple rigid bodies connected by constraints, and using (for example) matrix-palette skinning to generate a surface mesh for rendering. This is the approach used for deformable objects in Havok Destruction . [ 20 ]
In the context of computer graphics, cloth simulation refers to the simulation of soft bodies in the form of two dimensional continuum elastic membranes, that is, for this purpose, the actual structure of real cloth on the yarn level can be ignored (though modeling cloth on the yarn level has been tried). [ 21 ] Via rendering effects, this can produce a visually plausible emulation of textiles and clothing , used in a variety of contexts in video games, animation, and film. It can also be used to simulate two dimensional sheets of materials other than textiles, such as deformable metal panels or vegetation. In video games it is often used to enhance the realism of clothed animated characters .
Cloth simulators are generally based on mass-spring models , but a distinction must be made between force-based and position-based solvers.
The mass-spring model (obtained from a polygonal mesh representation of the cloth) determines the internal spring forces acting on the nodes at each timestep (in combination with gravity and applied forces). Newton's second law gives equations of motion which can be solved via standard ODE solvers. To create high resolution cloth with a realistic stiffness is not possible however with simple explicit solvers (such as forward Euler integration ), unless the timestep is made too small for interactive applications (since as is well known [ citation needed ] , explicit integrators are numerically unstable for sufficiently stiff systems). Therefore, implicit solvers must be used, [ 22 ] requiring solution of a large sparse matrix system (via e.g. the conjugate gradient method ), which itself may also be difficult to achieve at interactive frame rates. An alternative [ 23 ] [ 24 ] is to use an explicit method with low stiffness, with ad hoc methods to avoid instability and excessive stretching (e.g. strain limiting corrections).
To avoid needing to do an expensive implicit solution of a system of ODEs , many real-time cloth simulators (notably PhysX , Havok Cloth , and Maya nCloth ) use position based dynamics (PBD), [ 25 ] an approach based on constraint relaxation. The mass-spring model is converted into a system of constraints, which demands that the distance between the connected nodes be equal to the initial distance. This system is solved sequentially and iteratively, by directly moving nodes to satisfy each constraint, until sufficiently stiff cloth is obtained. This is similar to a Gauss-Seidel solution of the implicit matrix system for the mass-spring model. Care must be taken though to solve the constraints in the same sequence each timestep, to avoid spurious oscillations, and to make sure that the constraints do not violate linear and angular momentum conservation. Additional position constraints can be applied, for example to keep the nodes within desired regions of space (sufficiently close to an animated model for example), or to maintain the body's overall shape via shape matching.
Realistic interaction of simulated soft objects with their environment may be important for obtaining visually realistic results. Cloth self-intersection is important in some applications for acceptably realistic simulated garments. This is challenging to achieve at interactive frame rates, particularly in the case of detecting and resolving self collisions and mutual collisions between two or more deformable objects.
Collision detection may be discrete/a posteriori (meaning objects are advanced in time through a pre-determined interval, and then any penetrations detected and resolved), or continuous/a priori (objects are advanced only until a collision occurs, and the collision is handled before proceeding). The former is easier to implement and faster, but leads to failure to detect collisions (or detection of spurious collisions) if objects move fast enough. Real-time systems generally have to use discrete collision detection, with other ad hoc ways to avoid failing to detect collisions.
Detection of collisions between cloth and environmental objects with a well defined "inside" is straightforward since the system can detect unambiguously whether the cloth mesh vertices and faces are intersecting the body and resolve them accordingly. If a well defined "inside" does not exist (e.g. in the case of collision with a mesh which does not form a closed boundary), an "inside" may be constructed via extrusion. Mutual- or self-collisions of soft bodies defined by tetrahedra is straightforward, since it reduces to detection of collisions between solid tetrahedra.
However, detection of collisions between two polygonal cloths (or collision of a cloth with itself) via discrete collision detection is much more difficult, since there is no unambiguous way to locally detect after a timestep whether a cloth node which has penetrated is on the "wrong" side or not. Solutions involve either using the history of the cloth motion to determine if an intersection event has occurred, or doing a global analysis of the cloth state to detect and resolve self-intersections. Pixar has presented a method which uses a global topological analysis of mesh intersections in configuration space to detect and resolve self-interpenetration of cloth. [ 26 ] Currently, this is generally too computationally expensive for real-time cloth systems.
To do collision detection efficiently, primitives which are certainly not colliding must be identified as soon as possible and discarded from consideration to avoid wasting time.
To do this, some form of spatial subdivision scheme is essential, to avoid a brute force test of O [ n 2 ] {\displaystyle O[n^{2}]} primitive collisions. Approaches used include:
Other effects which may be simulated via the methods of soft-body dynamics are:
Simulating fluids in the context of computer graphics would not normally be considered soft-body dynamics, which is usually restricted to mean simulation of materials which have a tendency to retain their shape and form. In contrast, a fluid assumes the shape of whatever vessel contains it, as the particles are bound together by relatively weak forces. | https://en.wikipedia.org/wiki/Soft-body_dynamics |
A soft-in soft-out decoder ( SISO decoder ) is a type of soft-decision decoder used with error correcting codes . [ 1 ] "Soft-in" refers to the fact that the incoming data may take on values other than 0 or 1, in order to indicate reliability. "Soft-out" refers to the fact that each bit in the decoded output also takes on a value indicating reliability. Typically, the soft output is used as the soft input to an outer decoder in a system using concatenated codes , or to modify the input to a further decoding iteration such as in the decoding of turbo codes .
Examples include the BCJR algorithm and the soft output Viterbi algorithm . | https://en.wikipedia.org/wiki/Soft-in_soft-out_decoder |
Soft foot is a common term used for machine frame distortion. The distortion is caused when one or more foot of a machine differ in height from the others. This in turn may be due to differences when the machine was manufactured, a squishy footage with oil film etc. between foot and base, a bent foot, or it may be induced by a pipe to which the machine is attached (e.g. a pipe on top of a pump), which prevents the machine from touching all its feet to its base.
Soft foot usually gives rise to a 1x harmonic of the rotation frequency in the spectrum when radial (horizontal or vertical) vibration measurements are taken. It can be detected in this way.
Similar harmonic 1x is caused by misalignment and looseness. Usually not only will it resemble them, but it also causes misalignment, imbalance and other problems. In fact, it may be loose, not strictly a soft foot. Therefore, a way to tell the difference is needed.
To differentiate soft foot from misalignment and looseness, even if it causes misalignment when present, one way is to loosen each foot bolt at a time, while the other three are tight. If loosening one of them reduces vibration amplitude (which would be opposite to what one would expect if the machine was all right and we caused looseness by unscrewing of the bolt), then soft foot was present.
Another way to differentiate soft foot from looseness are phase measurements between the machine foot and the base/ground. 180 degrees difference indicates looseness.
Soft foot can be detected by using a variety of methods, including:
Once soft foot has been detected, it can be corrected by shimming the machine feet until all four feet are in solid contact with the foundation or baseplate. | https://en.wikipedia.org/wiki/Soft_Foot |
Soft Ionization by Chemical Reaction in Transfer is a method for ionizing small organic compounds at ambient atmospheric pressure . It is used for ion generation in mass spectrometers (MS).
The technique is often abbreviated as SICRIT, a trademark of Plasmion GmbH, [ 1 ] which commercialized the technique in the 2020s. [ 2 ]
Sicrit ionizes molecules through a technique known as dielectric barrier discharge . This process involves creating an electrical discharge between two electrodes that are separated by a dielectric . The electrodes are a stainless-steel tube placed inside a copper tube, with a thin quartz tube separating them. The sample containing the molecules to be ionized flows through the quartz tube separating the electrodes. A voltage is applied to the electrodes; the resulting electrical discharge ignites a cold plasma which ionizes the sample. [ 3 ]
Unlike other ambient ionization methods such as DART , DAPPI or DESI , SICRIT takes place directly in line with the inlet system of the MS and thus in a continuous flow:
Several reaction pathways have been identified that lead to ionization during this process: [ 4 ]
Regardless of the specific reaction pathway, almost exclusively protonated species [M+H]+ are generated during ionization.
Since the analytes do not come into direct contact with the plasma during ionization, but rather charge transfer occurs via reactive species and UV radiation, the molecules remain intact and fragmentation is avoided. Consequently, SICRIT is a very "soft" ionization method.
The SICRIT technology decouples sample delivery from the ionization process. Through the flow principle, the sample is directly drawn into the high vacuum behind the MS inlet and ionized on its way into the inlet. The electrode geometry is chosen so that, under the given physical parameters (pressure, ignition voltage, gas constant, see Paschen's law ), flexibility regarding the plasma medium is ensured. This allows the generation of stable cold plasma even in ambient air. In the simplest application, ambient air can be directly analyzed.
Ionization in flow enables high ion transmission since ion loss is significantly reduced compared to the most commonly used spraying methods in mass spectrometry (cf. ESI , APCI ). Consequently, this leads to an increase in sensitivity compared to these methods.
Ionization in flow also allows for real-time measurement without the need for sample preparation. Simple screening applications, especially for volatile organic compound analysis, can be easily implemented since the usual sample preparation (including crushing, extraction, purification, etc.) becomes obsolete for simple screening applications.
The different reaction pathways in plasma ionization broaden the spectrum of ionizable substances. This means that compared to ionization methods that only allow for single reaction pathways, a wider polarity range of analytes is covered, and nonpolar substances such as hexane can be ionized.
The low fragmentation ionization allows for identification based on the molecular mass as protonated [M+H]+ species. This can be particularly useful in combination with high-resolution mass spectrometers such as time-of-flight mass spectrometers (TOF-MS) or Orbitrap-MS for non-target analysis, where the entire substance spectrum of a sample is captured based on the exact mass of the molecules. [ 5 ]
Thus, SICRIT can be used in combination with both liquid chromatography (LC) as well as gas chromatography (GC). This enables the performance of both LC-MS and GC-MS analyses on the same mass spectrometer and the establishment of a unified database for comparing data from these otherwise instrumentally separated separation and detection methods.
As ambient ionization, SICRIT technology enables direct, real-time gas phase measurement using a mass spectrometer. The sample is positioned directly in front of the SICRIT source without any preparation. One application area is the measurement of aromatic compounds. [ 6 ]
The SICRIT ion source allows for coupling with various types of chromatography (GC, HPLC , SFC , etc.) as interface technology to any atmospheric pressure mass spectrometer (LC-MS). The ionization with its characteristics (see above) is not influenced by the coupling, allowing the same ionization method to be used for different chromatography couplings. The ability to couple gas chromatography with a low-fragmentation ionization technique on an LC-MS, for example, can be utilized in the analysis of saturated hydrocarbons . Electron impact ionization commonly used in GC-MS leads to difficult-to-interpret fragmentation spectra, while plasma ionization provides fragmentation-free spectra. [ 7 ] Thus, the DBD plasma with its broad ionization range opens up new fields of application possibilities for LC mass spectrometers in residue analysis, such as pesticides, where gas chromatographic separation is the method of choice and plasma ionization achieves very low detection limits. [ 8 ]
In combination with appropriate sample preparation and instrumentation, the SICRIT ion source can also be used for imaging mass spectrometry. The standard procedure typically involves elaborate sample preparation combined with laser desorption/ionization (e.g., MALDI or atmospheric pressure MALDI ), allowing spatial visualization of biomolecules, for example, in tissue sections. [ 9 ]
The use of the SICRIT source for additional in-line post-ionization in AP-MALDI experiments can result in significant signal enhancement in the detection of metabolites in biological sample material or enables detection of small (bio)molecules that are not addressable using MALDI alone. [ 9 ]
Furthermore, the SICRIT ion source enables spatially resolved analysis of unprepared samples in laser ablation experiments (cf. Fig. 3). The analytes released by laser bombardment are ionized directly with the SICRIT ion source, and the spatially resolved data are translated into two-dimensional images. This provides information, for example, on the distribution of active ingredients in tablets. [ 10 ]
In combination with a flow cytometer , the SICRIT ion source also enables the analysis of individual cells. The separated cell is introduced into the mass spectrometer through the ion source, and the lysate released upon cell rupture is analyzed. More precisely, the molecules contained in the lysate (mostly lipids) are ionized. | https://en.wikipedia.org/wiki/Soft_Ionization_by_Chemical_Reaction_in_Transfer |
Soft Matter is a peer-reviewed scientific journal covering the science of soft matter . It is published by the Royal Society of Chemistry and the editor-in-chief is Darrin Pochan ( University of Delaware , USA).
The journal was established in 2005. Initially it was published monthly, but as submissions increased it switched to 24 issues a year in 2009 [ 1 ] and to 48 issues a year in 2012.
The journal is abstracted and indexed in:
According to the Journal Citation Reports , the journal has a 2021 impact factor of 4.046. [ 5 ] | https://en.wikipedia.org/wiki/Soft_Matter_(journal) |
In theoretical physics , soft SUSY breaking is type of supersymmetry breaking that does not cause ultraviolet divergences to appear in scalar masses.
These terms are relevant operators —i.e. operators whose coefficients have a positive dimension of mass—though there are some exceptions.
A model with soft SUSY breaking was proposed in 1981 by Howard Georgi and Savas Dimopoulos . [ 1 ] Before this, dynamical models of supersymmetry breaking were being used that suffered from giving rise to color and charge breaking vacua.
Soft SUSY breaking decouples the origin of supersymmetry breaking from its phenomenological consequences. In effect, soft SUSY breaking adds explicit symmetry breaking to the supersymmetric Standard Model Lagrangian. The source of SUSY breaking results from a different sector where supersymmetry is broken spontaneously. Divorcing the spontaneous supersymmetry breaking from the supersymmetric Standard Model leads to the notion of mediated supersymmetry breaking.
In low energy supersymmetry based models, the soft supersymmetry breaking interactions excepting the mass terms are usually considered to be holomorphic functions of fields. While a superpotential such as that of MSSM needs to be holomorphic, there is no reason why soft supersymmetry breaking interactions are required to be holomorphic functions of fields. [ 2 ] Of course, an arbitrary nonholomorphic interaction may invite an appearance of quadratic divergence (or hard supersymmetry breaking); however, there are scenarios with no gauge singlet fields where nonholomorphic interactions can as well be of soft supersymmetry breaking type. [ 3 ] One may consider a hidden sector based supersymmetry breaking, with X {\displaystyle X} and Φ {\displaystyle \Phi } to be chiral superfields . Then, there exist nonholomorphic D {\displaystyle D} -term contributions of the forms 1 M 3 [ X X ∗ Φ 2 Φ ∗ ] D {\displaystyle {\frac {1}{M^{3}}}[XX^{*}\Phi ^{2}\Phi ^{*}]_{D}} and 1 M 3 [ X X ∗ D α Φ D α Φ ] D {\displaystyle {\frac {1}{M^{3}}}[XX^{*}D^{\alpha }\Phi D_{\alpha }\Phi ]_{D}} that are soft supersymmetry breaking in nature. The above lead to nonholomorphic trilinear soft terms like ϕ 2 ϕ ∗ {\displaystyle \phi ^{2}\phi ^{*}} and an explicit Higgsino soft mass term like ψ ψ {\displaystyle \psi \psi } in the Lagrangian. The coefficients of both ϕ 2 ϕ ∗ {\displaystyle \phi ^{2}\phi ^{*}} and ψ ψ {\displaystyle \psi \psi } terms are proportional to | F | 2 M 3 {\displaystyle {\frac {|F|^{2}}{M^{3}}}} , where | F | {\displaystyle |F|} is the vacuum expectation value of the auxiliary field components of X {\displaystyle X} and M {\displaystyle M} is the scale of mediation of supersymmetry breaking. Away from MSSM, there can be higgsino-gaugino interactions like ψ λ {\displaystyle \psi \lambda } that are also nonholomorphic in nature.
This quantum mechanics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Soft_SUSY_breaking |
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce images of very small objects.
Unlike visible light , X-rays do not reflect or refract easily, and they are invisible to the human eye. Therefore, the basic process of an X-ray microscope is to expose film or use a charge-coupled device (CCD) detector to detect X-rays that pass through the specimen. It is a contrast imaging technology using the difference in absorption of soft X-ray in the water window region (wavelength region: 2.34–4.4 nm, photon energy region: 280 – 530 eV) by the carbon atom (main element composing the living cell) and the oxygen atom (main element for water).
Early X-ray microscopes by Paul Kirkpatrick and Albert Baez used grazing incidence reflective optics to focus the X-rays, which grazed X-rays off parabolic curved mirrors at a very high angle of incidence . An alternative method of focusing X-rays is to use a tiny fresnel zone plate of concentric gold or nickel rings on a silicon dioxide substrate. Sir Lawrence Bragg produced some of the first usable X-ray images with his apparatus in the late 1940s.
In the 1950s Newberry produced a shadow X-ray microscope which placed the specimen between the source and a target plate, this became the basis for the first commercial X-ray microscopes from the General Electric Company .
The Advanced Light Source (ALS) in Berkeley, California, is home to XM-1 ( http://www.cxro.lbl.gov/BL612/ ), a full field soft X-ray microscope operated by the Center for X-ray Optics and dedicated to various applications in modern nanoscience, such as nanomagnetic materials, environmental and materials sciences and biology. XM-1 uses an X-ray lens to focus X-rays on a CCD, in a manner similar to an optical microscope. XM-1 held the world record in spatial resolution with Fresnel zone plates down to 15 nm and is able to combine high spatial resolution with a sub-100ps time resolution to study e.g. ultrafast spin dynamics. In July 2012, a group at DESY claimed a record spatial resolution of 10 nm, by using the hard X-ray scanning microscope at PETRA III. [ 1 ]
The ALS is also home to the world's first soft X-ray microscope designed for biological and biomedical research. This new instrument, XM-2 was designed and built by scientists from the National Center for X-ray Tomography. XM-2 is capable of producing 3-Dimensional tomograms of cells.
Sources of soft X-rays suitable for microscopy, such as synchrotron radiation sources, have fairly low brightness of the required wavelengths, so an alternative method of image formation is scanning transmission soft X-ray microscopy. Here the X-rays are focused to a point and the sample is mechanically scanned through the produced focal spot. At each point the transmitted X-rays are recorded with a detector such as a proportional counter or an avalanche photodiode . This type of Scanning Transmission X-ray Microscope (STXM) was first developed by researchers at Stony Brook University and was employed at the National Synchrotron Light Source at Brookhaven National Laboratory .
The resolution of X-ray microscopy lies between that of the optical microscope and the electron microscope . It has an advantage over conventional electron microscopy in that it can view biological samples in their natural state. Electron microscopy is widely used to obtain images with nanometer level resolution but the relatively thick living cell cannot be observed as the sample has to be chemically fixed, dehydrated, embedded in resin, then sliced ultra thin. However, it should be mentioned that cryo-electron microscopy allows the observation of biological specimens in their hydrated natural state, albeit embedded in water ice. Until now, resolutions of 30 nanometer are possible using the Fresnel zone plate lens which forms the image using the soft X-rays emitted from a synchrotron. Recently, the use of soft X-rays emitted from laser-produced plasmas rather than synchrotron radiation is becoming more popular.
Additionally, X-rays cause fluorescence in most materials, and these emissions can be analyzed to determine the chemical elements of an imaged object. Another use is to generate diffraction patterns, a process used in X-ray crystallography . By analyzing the internal reflections of a diffraction pattern (usually with a computer program), the three-dimensional structure of a crystal can be determined down to the placement of individual atoms within its molecules. X-ray microscopes are sometimes used for these analyses because the samples are too small to be analyzed in any other way. | https://en.wikipedia.org/wiki/Soft_X-ray_microscopy |
In mathematics , a soft cell is a shape with curved edges that can tile the 2D plane or 3D space. [ 1 ] The class of shapes was discovered in 2024 by Gábor Domokos , Alain Goriely , Ákos G. Horváth and Krisztina Regős. [ 2 ] [ 3 ]
The shapes are found in a wide variety of phenomena in nature, such as river estuaries , muscle fibres , and the seashell chambers of the nautilus . [ 4 ] [ 5 ] | https://en.wikipedia.org/wiki/Soft_cell |
Soft chemistry (also known as chimie douce ) is a type of chemistry that uses reactions at ambient temperature in open reaction vessels with reactions similar to those occurring in biological systems. [ 1 ] [ 2 ]
The aim of the soft chemistry is to synthesize materials , [ 3 ] drawing capacity of living beings - more or less basic - such as diatoms capable of producing glass from silicates dissolved. It is a new branch of materials science that differs from conventional solid-state chemistry and its application to the intense energy to explore the chemical inventiveness of the living world. This specialty emerged in the 1980s around the label of "chimie douce", which was first published by the French chemist, Jacques Livage [ 4 ] in Le Monde , 26 October 1977. [ 5 ] French hits, the term soft chemistry is employed as such in the early twenty-first century in scientific publications , English and others. His mode of synthesis is similar generally for reactions involved in the polymerizations based on organic and the establishment of solutions reactive energy intake without essential polycondensation . The fundamental interest of this kind of polymerization mineral obtained at room temperature is to preserve organic molecules or microorganisms that wishes to fit. The products obtained by means of the so-called soft chemistry sol-gel can be stored in several types:
The early results have included the creation of glasses and ceramic with new properties. These different structures are more or less composite mobilized a wide range of applications ranging from health to the needs of the conquest of space. Beyond its mode of synthesis, a compound with the label soft chemistry combines the advantages of the mineral (resistance, transparency, repetition patterns, etc.) and now exploring the potential of the biochemistry and organic chemistry (interface with the organic world, reactivity, synthesis capability, etc.). According to its practitioners, "soft chemistry" is only in its early success and opens up vast prospects. | https://en.wikipedia.org/wiki/Soft_chemistry |
Soft Cost is a construction industry term but more specifically a contractor accounting term for an expense item that is not considered direct construction cost. Soft costs include architectural, engineering, financing, and legal fees, and other pre- and post-construction expenses. [ 1 ] The term has been replaced in most contractor accrual accounting with the term General & Administrative abbreviated G&A.
For a contractor, soft costs are essentially construction costs incurred that are not labor and materials. Delay in Start Up insurance coverage and soft costs are not the same. Some soft costs may be incurred in the repair of a covered loss before the anticipated completion date is reached. These can be architect fees or engineering fees incurred to repair loss or damage to the insured property. Only those indirect costs that are above what would have been incurred up to the anticipated completion date but continue after such date due to the insured delay are soft costs that are covered by delay in completion or delay in start up coverage. Soft cost is a contractor accounting term for their expenses that are not associated with a particular construction task. Their construction trailer, water delivery, book keepers, etc. are all soft costs that continue on after the original anticipated completion date is reached, if the project is delayed. Only if the delay was caused by an insured loss would the insurance pick these expenses up, and only if the policy includes delay in start up coverage. Any repair costs which are not labor or materials and are indemnified to complete the repair of property loss should not be reported under delay in completion and there is no delay in completion until the anticipated date of completion is reached, and the project is not finished. Not all indirect costs are time related expenses that continue after the original date of completion. Those soft costs (indirect costs) which are continuing fixed expenses that continue because the project is delayed by an insured loss are soft costs that should be included with the delay in start up values. A soft cost to a contractor , such as his administration costs, can be a hard cost to the owner because what the contractor invoices the owner is the owner's direct cost. If the owner employs engineers to overlook construction as the project is executed, this will be a continuing expense during repair if the repair is done after the original completion date and would be reported in the delay in completion values. If the engineer cost was a one time charge for a design, he may need to be consulted in order for the loss to be repaired. This expense does not occur because of a delay, but is incurred to repair property damage and hence should be included in the construction costs if the intention is for that expense to be covered in the indemnification depending on policy wording. If the project is insured to the extent of the reported values, and that value was left out to compute the premium, the company may decline that cost in the indemnification.
Soft costs differ from hard costs in both labor and materials; they are generally not considered to be exclusively related to physical construction. Rather, they are commonly perceived to entail non-construction costs such as taxes , marketing expenses, interest payments, and finance charges. The soft costs endorsement provided in the Builders’ Risk section of the AAIS Inland Marine Guide lists 10 types of soft costs: advertising, design fees, professional fees, financing, lease administration, real estate taxes, general administration, lease expenses, permit fees, and insurance premiums. [ 2 ]
In recent years, a solution to the problem has emerged in the form of Delay in Opening coverage which can be provided in Builder's Risk Insurance . This coverage can provide indemnification for these indirect costs that may continue after the original completion date. Other soft costs that can be repeated in the repair of the property should be reported with the property values. A Draw Back expense proforma shows which soft costs are one time charges and which are continuing expenses throughout the project term. Engineer design fee is a one time charge that can be incurred again in a repair whereas engineer oversight of quality persists through the term and after.
Unfortunately, these contractor accounting terms are being used when the owner is insured and many have erroneously equated hard costs with property and soft costs with business interruption which is called Delay in Opening [ 3 ] coverage being added to some builder's risk policies. With its popularity increasing in recent years, some insurers automatically include soft costs coverage, which can be activated by designating the limit on policy declarations. However, these modifications to builder's risk insurance will not cover the efficiency of business owners or managers. Soft costs can also refer to the failure of implementing a strategy in a timely manner, or the opportunity cost of delaying a solution to a problem for discussion or consideration. For this reason, it is important to understand that soft costs can refer to unforeseen construction costs (lost screws, damaged equipment), physical labor (task takes longer than expected, losing a key team member), or time wasted on strategy implementation (taking too long to decide a course of action). [ 4 ] | https://en.wikipedia.org/wiki/Soft_costs |
A soft gamma repeater ( SGR ) is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them. [ 1 ]
On March 5, 1979 [ 2 ] a powerful gamma-ray burst was noted. As a number of receivers at different locations in the Solar System [ 3 ] saw the burst at slightly different times, its direction could be determined, and it was shown to originate from near a supernova remnant in the Large Magellanic Cloud . [ 2 ] [ 3 ]
Over time it became clear that this was not a normal gamma-ray burst. The photons were less energetic in the soft gamma-ray and hard X-ray range, and repeated bursts came from the same region.
Astronomer Chryssa Kouveliotou of the Universities Space Research Association (USRA) at NASA's Marshall Space Flight Center decided to test the hypothesis that soft gamma repeaters were magnetars. [ 2 ] [ 3 ] According to the hypothesis, the bursts would cause the object to slow down its rotation. In 1998, [ 2 ] [ 3 ] she made careful comparisons of the periodicity of soft gamma repeater SGR 1806-20 . The period had increased by 0.008 seconds since 1993, and she calculated that this would be explained by a magnetar with a magnetic-field strength of 8×10 10 teslas (8×10 14 gauss ). This was enough to convince the international astronomical community that soft gamma repeaters are indeed magnetars.
An unusually spectacular soft gamma repeater burst was SGR 1900+14 observed on August 27, 1998. Despite the large distance to this SGR, estimated at 20,000 light years, the burst had large effects on the Earth's atmosphere. The atoms in the ionosphere , which are usually ionized by the Sun's radiation by day and recombine to neutral atoms by night, were ionized at nighttime at levels not much lower than the normal daytime level. The Rossi X-Ray Timing Explorer ( RXTE ), an X-ray satellite , received its strongest signal from this burst at this time, even though it was directed at a different part of the sky, and should normally have been shielded from the radiation.
Known soft gamma repeaters include: [ 4 ]
The numbers give the position in the sky, for example, SGR 0525-66 has a right ascension of 5h25m and a declination of −66°. The date of discovery sometimes appears in a format such as 1979/1986 to refer to the year the object was discovered, in addition to the year soft gamma repeaters were recognized as a separate class of objects rather than "normal" gamma-ray bursts. | https://en.wikipedia.org/wiki/Soft_gamma_repeater |
Soft handover or soft handoff refers to a feature used by the CDMA and W-CDMA standards, [ 1 ] [ 2 ] where a cell phone is simultaneously connected to two or more cells (or cell sectors) during a call. If the sectors are from the same physical cell site (a sectorised site), it is referred to as softer handoff . This technique is a form of mobile-assisted handover, for IS-95 / CDMA2000 CDMA cell phones continuously make power measurements of a list of neighboring cell sites, and determine whether or not to request or end soft handover with the cell sectors on the list.
Due to the properties of the CDMA signaling scheme, it is possible for a CDMA phone to simultaneously receive signals from two or more radio base stations that are transmitting the same bit stream (using different transmission codes) on the different physical channels in the same frequency bandwidth. If the signal power from two or more radio base stations is nearly the same, the phone receiver can combine the received signals in such a way that the bit stream is decoded much more reliably than if only one base station were transmitting to the subscriber station. If any one of these signals fades significantly, there will be a relatively high probability of having adequate signal strength from one of the other radio base stations.
On the uplink (phone-to-cell-site), all the cell site sectors that are actively supporting a call in soft handover send the bit stream that they receive back to the Radio Network Controller (RNC), along with information about the quality of the received bits . The RNC examines the quality of all these bit streams and dynamically chooses the bit stream with the highest quality. Again, if the signal degrades rapidly, the chance is still good that a strong signal will be available at one of the other cell sectors that is supporting the call in soft handover .
Soft handover results in a diversity gain [ 3 ] called soft handover gain. | https://en.wikipedia.org/wiki/Soft_handover |
Soft infrastructure is all the services that are required to maintain the economic, health, cultural and social standards of a population, as opposed to the hard infrastructure , which is the physical infrastructure of roads, bridges etc. It includes both physical assets such as highly specialised buildings and equipment, as well as non-physical assets, such as communication, the body of rules and regulations governing the various systems, the financing of these systems, the systems and organisations by which professionals are trained, advance in their careers by acquiring experience, and are disciplined if required by professional associations. It includes institutions such as the financial and economic systems, the education system , the health care system , the system of government, and law enforcement , and emergency services .
The essence of soft infrastructure is the delivery of specialised services to people. Unlike much of the service sector of the economy, the delivery of those services depends on highly developed systems and large specialised facilities, fleets of specialised vehicles or institutions. [ 1 ] [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/Soft_infrastructure |
A soft launch , also known as a soft opening , is a preview release of a product or service to a limited audience prior to the general public . Soft-launching a product is sometimes used to gather data or customer feedback , prior to making it widely available during an official release or grand opening. A company may also choose a soft launch to test the functionality of a product, allowing adjustments to be made before a wider release and marketing efforts are implemented.
When implementing a soft launch strategy, a company releases a product with little or no marketing. A soft launch permits a company to react to customer demands quickly and effectively, introducing new features which will ultimately make the product successful. For companies with a limited budget, a soft launch can allow them to focus on product development rather than marketing.
Soft launches can be used with websites to help roll out new features, test or tweak a design (or possible redesign) allowing a design which users dislike to be quietly retired. Changes can also be made to increase the functionality of the website and respond to user requests. Gmail , for example, was soft launched in 2005 and fully launched one year later.
In the instance of hardware products, a limited release soft launch can be used to test the market prior to a wide scale release. It also means companies are allowed to make last minute changes to the product after the soft launch. In many instances, soft launches of hardware are done in major metropolitan areas where the company has access to a wide variety of demographic groups.
Soft launches are also used for software, with a small release being made to a limited group of individuals for beta testing . Software can be extensively tested by the releasing company, but ultimately it needs to be used to determine how effective it is. Major flaws in the design may emerge during beta testing and can be corrected before the product is released into a major market.
Some software is soft launched on the Internet, which allows for easy software updates . Early beta testers can grow attached to the program and will continue to download new versions as they are released. Thus, companies often build up a loyal customer base, which spreads the word to other potential customers. [ citation needed ]
Soft launches are popular for free-to-play mobile games . [ 1 ]
Before committing to a hard launch in the United States , developers creating English mobile applications may choose to launch unofficially in less populous English-speaking countries in order to refine it before launch by analyzing usage and spending habits, which are thought to be similar to those in the United States. [ citation needed ] This may also reduce the chances of the American press noticing the app. [ citation needed ] While predominantly English-speaking countries like Canada, Australia, and New Zealand are common choices, games are also tested in countries like the Philippines, which has connections to Asia; Sweden, which can provide an on-ramp into the European market; and many other countries including Brazil, South Africa, and Indonesia. [ 1 ] Canada, in particular, also has the advantage of having similar time zones to the United States. [ citation needed ]
A soft launch differs significantly from a hard launch (also known as a "grand opening" or "full launch") in several key aspects. While a soft launch targets a limited, select audience, a hard launch aims for the general public with a wide release. Soft launches typically involve minimal or no marketing , whereas hard launches are accompanied by extensive marketing campaigns .
The duration of these launch strategies also varies. Soft launches extend over a period, allowing for testing and refinement, while hard launches are often centered around a single event or short-term push. The primary purpose of a soft launch is to gather feedback, test functionality, and make adjustments. In contrast, a hard launch focuses on official release and maximizing impact and awareness.
Visibility is another distinguishing factor. Soft launches are typically low-key and often fly under the radar, while hard launches are high-profile events seeking attention. Soft launches offer high flexibility, allowing for changes based on feedback, whereas hard launches present the product or service as final with little room for major adjustments. [ 2 ]
Resource investment often differs between the two approaches. Soft launches generally require lower initial investment, while hard launches often demand significant upfront resources. This correlates with the level of risk: soft launches carry lower risk as issues can be addressed before full release, but hard launches involve higher risk due to less room for major adjustments post-launch.
Businesses may choose to use a soft launch, hard launch, or a combination of both strategies depending on factors such as product readiness, market conditions, available resources, risk tolerance , brand strategy, and the nature of the product or service. While soft launches allow for more flexibility and risk mitigation, hard launches can create more immediate impact and awareness. The choice between the two approaches often depends on the specific goals and circumstances of the release.
When a brick and mortar business wishes to open prior to its grand opening (to test its capacity and train its staff), this may be referred to as a soft launch or "soft opening".
When a business wishes to close but still allow customers to shop, this is referred to as a "soft close".
The term test event is often used in sports, especially in the UK , to refer to events held in a newly constructed sports venue before its official opening. For example, a newly built venue in the UK is required to host two events at reduced capacity, with the second event using a larger capacity than the first, before being granted a safety certificate that allows it to hold events at full capacity. [ 3 ]
The term "soft launch" has been used by social media influencers to hint at the existence of a significant other without making a formal announcement, as a subtler alternative to a "boyfriend reveal". Examples can include posting pictures of food or drink for two or a selfie in an unfamiliar location. [ 4 ] | https://en.wikipedia.org/wiki/Soft_launch |
Soft matter or soft condensed matter is a type of matter that can be deformed or structurally altered by thermal or mechanical stress which is of similar magnitude to thermal fluctuations .
The science of soft matter is a subfield of condensed matter physics . Soft materials include liquids , colloids , polymers , foams , gels , granular materials , liquid crystals , flesh , and a number of biomaterials . These materials share an important common feature in that predominant physical behaviors occur at an energy scale comparable with room temperature thermal energy (of order of kT ), and that entropy is considered the dominant factor. [ 1 ] At these temperatures, quantum aspects are generally unimportant. When soft materials interact favorably with surfaces, they become squashed without an external compressive force. [ 2 ]
Pierre-Gilles de Gennes , who has been called the "founding father of soft matter," [ 3 ] received the Nobel Prize in Physics in 1991 for discovering that methods developed for studying order phenomena in simple systems can be generalized to the more complex cases found in soft matter, in particular, to the behaviors of liquid crystals and polymers . [ 4 ]
The current understanding of soft matter grew from Albert Einstein's work on Brownian motion , [ 5 ] [ 6 ] understanding that a particle suspended in a fluid must have a similar thermal energy to the fluid itself (of order of kT ). This work built on established research into systems that would now be considered colloids. [ 7 ]
The crystalline optical properties of liquid crystals and their ability to flow were first described by Friedrich Reinitzer in 1888, [ 8 ] and further characterized by Otto Lehmann in 1889. [ 9 ] The experimental setup that Lehmann used to investigate the two melting points of cholesteryl benzoate are still used in the research of liquid crystals as of about 2019. [ 10 ]
In 1920, Hermann Staudinger , recipient of the 1953 Nobel Prize in Chemistry , [ 11 ] was the first person to suggest that polymers are formed through covalent bonds that link smaller molecules together. [ 12 ] The idea of a macromolecule was unheard of at the time, with the scientific consensus being that the recorded high molecular weights of compounds like natural rubber were instead due to particle aggregation . [ 13 ]
The use of hydrogel in the biomedical field was pioneered in 1960 by Drahoslav Lím and Otto Wichterle . [ 14 ] Together, they postulated that the chemical stability, ease of deformation, and permeability of certain polymer networks in aqueous environments would have a significant impact on medicine, and were the inventors of the soft contact lens . [ 15 ]
These seemingly separate fields were dramatically influenced and brought together by Pierre-Gilles de Gennes . The work of de Gennes across different forms of soft matter was key to understanding its universality , where material properties are not based on the chemistry of the underlying structure , more so on the mesoscopic structures the underlying chemistry creates. [ 16 ] He extended the understanding of phase changes in liquid crystals, introduced the idea of reptation regarding the relaxation of polymer systems, and successfully mapped polymer behavior to that of the Ising model . [ 16 ] [ 17 ]
Interesting behaviors arise from soft matter in ways that cannot be predicted, or are difficult to predict, directly from its atomic or molecular constituents. Materials termed soft matter exhibit this property due to a shared propensity of these materials to self-organize into mesoscopic physical structures. The assembly of the mesoscale structures that form the macroscale material is governed by low energies, and these low energy associations allow for the thermal and mechanical deformation of the material. [ 18 ] By way of contrast, in hard condensed matter physics it is often possible to predict the overall behavior of a material because the molecules are organized into a crystalline lattice with no changes in the pattern at any mesoscopic scale. Unlike hard materials, where only small distortions occur from thermal or mechanical agitation, soft matter can undergo local rearrangements of the microscopic building blocks. [ 19 ]
A defining characteristic of soft matter is the mesoscopic scale of physical structures. The structures are much larger than the microscopic scale (the arrangement of atoms and molecules ), and yet are much smaller than the macroscopic (overall) scale of the material. The properties and interactions of these mesoscopic structures may determine the macroscopic behavior of the material. [ 20 ] The large number of constituents forming these mesoscopic structures, and the large degrees of freedom this causes, results in a general disorder between the large-scale structures. This disorder leads to the loss of long-range order that is characteristic of hard matter. [ 21 ]
For example, the turbulent vortices that naturally occur within a flowing liquid are much smaller than the overall quantity of liquid and yet much larger than its individual molecules, and the emergence of these vortices controls the overall flowing behavior of the material. Also, the bubbles that compose a foam are mesoscopic because they individually consist of a vast number of molecules, and yet the foam itself consists of a great number of these bubbles, and the overall mechanical stiffness of the foam emerges from the combined interactions of the bubbles.
Typical bond energies in soft matter structures are of similar scale to thermal energies. Therefore the structures are constantly affected by thermal fluctuations and undergo Brownian motion . [ 20 ] The ease of deformation and influence of low energy interactions regularly result in slow dynamics of the mesoscopic structures which allows some systems to remain out of equilibrium in metastable states. [ 22 ] [ 23 ] This characteristic can allow for recovery of initial state through an external stimulus, which is often exploited in research. [ 24 ] [ 25 ]
Self-assembly is an inherent characteristic of soft matter systems. The characteristic complex behavior and hierarchical structures arise spontaneously as a system evolves towards equilibrium. [ 20 ] Self-assembly can be classified as static when the resulting structure is due to a free energy minimum, or dynamic when the system is caught in a metastable state. [ 26 ] Dynamic self-assembly can be utilized in the functional design of soft materials with these metastable states through kinetic trapping . [ 18 ] [ 27 ]
Soft materials often exhibit both elasticity and viscous responses to external stimuli [ 22 ] such as shear induced flow or phase transitions. However, excessive external stimuli often result in nonlinear responses. [ 1 ] [ 28 ] Soft matter becomes highly deformed before crack propagation , which differs significantly from the general fracture mechanics formulation. [ 19 ] Rheology , the study of deformation under stress , is often used to investigate the bulk properties of soft matter. [ 22 ]
Soft matter consists of a diverse range of interrelated systems and can be broadly categorized into certain classes. These classes are by no means distinct, as often there are overlaps between two or more groups.
Polymers are large molecules composed of repeating subunits whose characteristics are governed by their environment and composition. Polymers encompass synthetic plastics, natural fibers and rubbers, and biological proteins. Polymer research finds applications in nanotechnology , [ 29 ] [ 30 ] from materials science and drug delivery to protein crystallization . [ 24 ] [ 31 ]
Foams consist of a liquid or solid through which a gas has been dispersed to form cavities. This structure imparts a large surface-area-to-volume ratio on the system. [ 23 ] [ 32 ] Foams have found applications in insulation and textiles , [ 32 ] and are undergoing active research in the biomedical field of drug delivery and tissue engineering . [ 31 ] Foams are also used in automotive for water and dust sealing and noise reduction.
Gels consist of non-solvent- soluble 3D polymer scaffolds, which are covalently or physically cross-linked , that have a high solvent/content ratio. [ 33 ] [ 34 ] Research into functionalizing gels that are sensitive to mechanical and thermal stress, as well as solvent choice, has given rise to diverse structures with characteristics such as shape-memory , [ 35 ] or the ability to bind guest molecules selectively and reversibly. [ 34 ]
Colloids are non-soluble particles suspended in a medium, such as proteins in an aqueous solution. [ 36 ] Research into colloids is primarily focused on understanding the organization of matter, with the large structures of colloids, relative to individual molecules, large enough that they can be readily observed. [ 37 ]
Liquid crystals can consist of proteins, small molecules, or polymers, that can be manipulated to form cohesive order in a specific direction. [ 38 ] They exhibit liquid-like behavior in that they can flow , yet they can obtain close-to-crystal alignment. One feature of liquid crystals is their ability to spontaneously break symmetry . [ 39 ] Liquid crystals have found significant applications in optical devices such as liquid-crystal displays (LCD).
Biological membranes consist of individual phospholipid molecules that have self-assembled into a bilayer structure due to non-covalent interactions . The localized, low energy associated with the forming of the membrane allows for the elastic deformation of the large-scale structure. [ 40 ]
Due to the importance of mesoscale structures in the overarching properties of soft matter, experimental work is primarily focused on the bulk properties of the materials. Rheology is often used to investigate the physical changes of the material under stress. [ 22 ] Biological systems, such as protein crystallization, are often investigated through X-ray and neutron crystallography , [ 41 ] while nuclear magnetic resonance spectroscopy can be used in understanding the average structure and lipid mobility of membranes. [ 40 ]
Scattering techniques, such as wide-angle X-ray scattering , small-angle X-ray scattering , neutron scattering , and dynamic light scattering can also be used for materials when probing for the average properties of the constituents. These methods can determine particle-size distribution , shape, crystallinity and diffusion of the constituents in the system. [ 42 ] [ 43 ] There are limitations in the application of scattering techniques to some systems, as they can be more suited to isotropic and dilute samples. [ 42 ]
Computational methods are often employed to model and understand soft matter systems, as they have the ability to strictly control the composition and environment of the structures being investigated, as well as span from microscopic to macroscopic length scales. [ 21 ] Computational methods are limited, however, by their suitability to the system and must be regularly validated against experimental results to ensure accuracy. [ 21 ] The use of informatics in the prediction of soft matter properties is also a growing field in computer science thanks to the large amount of data available for soft matter systems. [ 44 ]
Optical microscopy can be used in the study of colloidal systems, but more advanced methods like transmission electron microscopy (TEM) and atomic force microscopy (AFM) are often used to characterize forms of soft matter due to their applicability to mapping systems at the nanoscale. [ 45 ] [ 46 ] These imaging techniques are not universally appropriate to all classes of soft matter and some systems may be more suited to one kind of analysis than another. For example, there are limited applications in imaging hydrogels with TEM due to the processes required for imaging. However, fluorescence microscopy can be readily applied. [ 42 ] Liquid crystals are often probed using polarized light microscopy to determine the ordering of the material under various conditions, such as temperature or electric field . [ 47 ]
Soft materials are important in a wide range of technological applications, and each soft material can often be associated with multiple disciplines. Liquid crystals, for example, were originally discovered in the biological sciences when the botanist and chemist Friedrich Reinitzer was investigating cholesterols . [ 10 ] Now, however, liquid crystals have also found applications as liquid-crystal displays , liquid crystal tunable filters , and liquid crystal thermometers . Active liquid crystals are another example of soft materials, where the constituent elements in liquid crystals can self-propel. [ 48 ]
Polymers have found diverse applications, from the natural rubber found in latex gloves to the vulcanized rubber found in tires. Polymers encompass a large range of soft matter, with applications in material science. An example of this is hydrogel. With the ability to undergo shear thinning , hydrogels are well suited for the development of 3D printing . [ 27 ] Due to their stimuli responsive behavior, 3D printing of hydrogels has found applications in a diverse range of fields, such as soft robotics , tissue engineering , and flexible electronics . [ 49 ] Polymers also encompass biological molecules such as proteins, where research insights from soft matter research have been applied to better understand topics like protein crystallization. [ 41 ]
3D/4D printing of soft materials is evolving, focusing on various printing techniques, material types, and their broad applications in engineering and technology. Key printing methods are extrusion and inkjet based printing, stereolithography, selective laser sintering, direct ink writing, and VAT photopolymerization. A diversity in soft materials for 3D/4D printing includes elastomers, hydrogels, bio-inspired polymers, conductive and flexible materials, andinkjet-based biomimetic materials for applications in biomedical engineering, soft robotics, wearable devices, textiles, food technology, and pharmaceuticals. Changelings and limitations prevail in design geometric complexity,cost, resolution, material #compatibility, scalability and regulatory concerns. [ 50 ]
Foams can naturally occur, such as the head on a beer , or be created intentionally, such as by fire extinguishers . The physical properties available to foams have resulted in applications which can be based on their viscosity, [ 23 ] with more rigid and self-supporting forms of foams being used as insulation or cushions , and foams that exhibit the ability to flow being used in the cosmetic industry as shampoos or makeup. [ 23 ] Foams have also found biomedical applications in tissue engineering as scaffolds and biosensors . [ 51 ]
Historically the problems considered in the early days of soft matter science were those pertaining to the biological sciences. As such, an important application of soft matter research is biophysics , with a major goal of the discipline being the reduction of the field of cell biology to the concepts of soft matter physics. [ 20 ] Applications of soft matter characteristics are used to understand biologically relevant topics such as membrane mobility, [ 40 ] as well as the rheology of blood . [ 36 ]
Media related to Soft matter at Wikimedia Commons | https://en.wikipedia.org/wiki/Soft_matter |
Soft privacy technologies fall under the category of PETs , Privacy-enhancing technologies, as methods of protecting data. Soft privacy is a counterpart to another subcategory of PETs, called hard privacy . Soft privacy technology has the goal of keeping information safe, allowing services to process data while having full control of how data is being used. To accomplish this, soft privacy emphasizes the use of third-party programs to protect privacy, emphasizing auditing, certification, consent, access control, encryption, and differential privacy. [ 1 ] Since evolving technologies like the internet, machine learning, and big data are being applied to many long-standing fields, we now need to process billions of datapoints every day in areas such as health care, autonomous cars, smart cards, social media, and more. Many of these fields rely on soft privacy technologies when they handle data.
Some medical devices like Ambient Assisted Living monitor and report sensitive information remotely into a cloud. [ 2 ] Cloud computing offers a solution that meets the healthcare need for processing and storage at an affordable price. [ 2 ] Together, this system is used to monitor a patient's biometric conditions remotely, connecting with smart technology when necessary. In addition to monitoring, the devices can also send a mobile notification when certain conditions pass a set point such as a major change in blood pressure. Due to the nature of these devices, which report data constantly and use smart technology, [ 3 ] this type of medical technology is subject to a lot of privacy concerns. Soft privacy is thus relevant for the third-party cloud service, as many privacy concerns center there, including risk in unauthorized access, data leakage, sensitive information disclosure, and privacy disclosure. [ 4 ]
One solution proposed for privacy issues around cloud computing in health care is through the use of Access control , by giving partial access to data based on a user's role: such as a doctor, family, etc. Another solution, applicable for wireless technology that moves data to a cloud, is through the usage of Differential privacy . [ 5 ] The differential privacy system typically encrypts the data, sends it to a trusted service, then opens up access to it for hospital institutions. A strategy that is often used to prevent data leakage and attacks works by adding ‘noise’ into the data which changes its values slightly. The real underlying information can be accessed through security questions. A study by Sensors concluded that differential privacy techniques involving additional noise helped achieve mathematically-precise guaranteed privacy. [ 5 ]
Adding noise to data by default can prevent devastating privacy breaches. In the mid-90's the Commonwealth of Massachusetts Group Insurance Commission released anonymous health records while hiding some sensitive information such as addresses and phone numbers. Despite this attempt to hiding personal information while providing a useful database, privacy was still breached–by correlating the health databases with public voting databases, individuals' hidden data could be rediscovered. Without the differential privacy techniques of encrypting data and adding noise, it is possible to link data that may not seem related, together. [ 6 ]
Autonomous cars raise concerns about location tracking, because they are sensor-based vehicles. To achieve full autonomy, these cars would need access to a massive database with information on the surroundings, paths to take, interaction with others, weather, and many more circumstances that need to be accounted for. This leads to privacy and security questions: how the data will all be stored, who is it shared with, and what type of data is being stored. A lot of this data is potentially sensitive and could be used maliciously if it was leaked or hacked. Additionally, there are concerns over this data being sold to companies, as the data can help predict products the consumer would like or need. This could be undesirable as data here may expose health conditions and alert some companies to advertise to said customers with location-based spam or products. [ 7 ]
In terms of the legal aspect of this technology, there are rules and regulations governing some parts of these cars, but for other areas, laws are left unwritten or oftentimes outdated. [ 8 ] Many of the current laws are vague, leaving the rules to be open to interpretation. For example, there are federal laws dating back many years ago governing computer privacy, which were extended to cover phones when they arose, and now are being extended again to apply to the “computer” inside most driverless cars. [ 8 ] Another legal concern surrounds government surveillance: can governments gain access to driverless car data, giving them the opportunity for mass surveillance or tracking with no warrants? Finally, companies may try to use this data to improve their technology and target their marketing data to fit the needs of their consumers. In response to this controversy, automakers pre-empted government action on driverless cars with the Automotive Information Sharing and Analysis Center (Auto-ISAC) in August 2015 [ 9 ] to establish protocols for cybersecurity and decide how to handle vehicular communication systems in a safe manner through with other autonomous cars.
Vehicle-to-grid , known as V2G, plays a big role in the energy consumption, cost, and effectiveness of smart grids. [ 10 ] This system is what electric vehicles use to charge and discharge, as they communicate with the power grid to fill up the appropriate amount. Although this ability is extremely important for electric vehicles, it does open up privacy issues surrounding the visibility of the car's location. For example, the driver's home address, place of work, place of entertainment, and record of frequency may be reflected in the car's charging history. With this information, which could potentially be leaked, there are a wide variety of security breaches that can occur. For example, someone’s health could be deduced by the car's number of hospital visits, or based on a user's parking patterns, they may receive location-based spam, or a thief could benefit from knowing their target's home address and work schedule. Like with handling sensitive health data, a possible solution here is to use differential privacy to add noise to the mathematical data so leaked information may not be as accurate.
Using the cloud is important for consumers and businesses, as it provides a cheap source of virtually unlimited storage space. One challenge cloud storage has faced was search functions. Typical cloud computing design would encrypt every word before it enters the cloud. If a user wants to search by keyword for a specific file stored in the cloud, the encryption hinders an easy and fast method of search. You can't scan the encrypted data for your search term anymore, because the keywords are all encrypted. So encryption ends up being a double-edged sword: it protects privacy but introduces new, inconvenient problems. [ 11 ] One performance solution lies in modifying the search method, so that documents are indexed entirely, rather than just their keywords. The search method can also be changed by searching with a term that gets encrypted, so that it can be matched to encrypted keywords without de-encrypting any data. In this case, privacy is achieved and it is easy to search for words that match with the encrypted files. However, there is a new issue that arises from this, as it takes a longer time to read and match through an encrypted file and decrypt the whole thing for a user. [ 11 ]
Police and other authorities also benefit from reading personal information from mobile data, which can be useful during investigations. [ 12 ] Privacy infringements and potential surveillance in these cases has often been a concern in the United States, and several cases have reached the Supreme Court. In some instances, authorities used GPS data to track down suspects' locations, and monitored data over long periods of time. This practice is now limited because of the Supreme Court case Riley v. California . There it was unanimously decided to prevent warrantless searches of mobile data.
Mobile privacy has also been an issue in the realm of spam calls. In the effort to reduce these calls, many people are being taken advantage of by apps that promise to help block spam. The problem with these apps is that many are known to collect personal phone data, including callers, phone honeypot call detail records (CDRs), and call recordings. Although some of this information is necessary for creating blacklists of spam, not all of it is, but these apps don't always prioritize privacy in their collection of data. As these are typically small-scaled apps with varying budget degrees, differential privacy is not always top of mind, and differential privacy, rather than ignoring privacy concerns, is often more expensive. This is because the dataset needed to construct a good algorithm that achieves local differential privacy is much larger than a basic dataset. [ 13 ]
VPNs are used to create a remote user and a home network and encrypt their package usage. This allows the user to have their own private network while on the internet. However, this encrypted tunnel must trust a third party to protect the privacy of the user, since it acts as a virtual leased line over the shared public infrastructure of the internet. Additionally, VPNs have a difficult time when it comes to mobile applications, because the cell network may be constantly changing and can even break, thus endangering the privacy that the VPN gives from its encryption. [ 14 ]
VPNs are susceptible to attackers that fabricate, intercept, modify, and interrupt traffic. They become a target, because sensitive information is often being transmitted over these networks. Quick VPNs generally provide faster tunnel establishment and less overhead, but they downgrade the effectiveness of VPNs as a security protocol. One mitigation centers around the simple practice of changing long usernames (IP addresses) and passwords frequently, which is important to achieving security and protection from malicious attacks. [ 15 ]
Newer smart cards are a developing technology used to authorize users for certain resources. [ 16 ] Using biometrics such as fingerprints, iris images, voice patterns, or even DNA sequences as access control for sensitive information such as a passport can help ensure privacy. Biometrics are important because they are basically unchangeable and can be used as the access code to one’s information, in some cases granting access to virtually any data about the particular person. Currently they are being used for telecommunications, e-commerce, banking applications, government applications, healthcare, transportation, and more.
Biometrics contain unique characteristic details about a person. If they are leaked, it would be fairly easy to trace the endangered user. This poses a great danger, because biometrics are based on features that rarely change, like a user's fingerprint, and many sensitive applications use biometrics. There are some possible solutions to this:
Anonymous Biometric Access Control System (ABAC) : This method authenticates valid users into the system without knowing who individuals are. For example, a hotel should be able to admit a VIP guest member into a VIP room without knowing any details about that person, even though the verification process is still utilizing biometrics. One way to do this was developed by the Center for Visualization and Virtual Environment. They designed an algorithm that uses techniques like hamming distance computation, bit extraction, comparison, and result aggregation, all implemented with a homomorphic cipher, to allow a biometric server to confirm a user without knowing their identity. This is done by taking the biometric saved and encrypting it. While saving the biometrics, there are specific processes to de-identify features such as facial recognition when encrypting the data so even if it was leaked, there would be no danger of tracing someone's identity. [ 17 ]
Online learning through videos has gotten very popular. One of the biggest challenges for privacy in this field is the practice of video prefetching. When a user selects an online video, rather than making them wait for it to slowly load, prefetching helps the user save time by loading part of the video before the user has even started watching. It seems to be a perfect and necessary solution as we stream more content, but prefetching faces privacy concerns because it heavily relies on prediction. For an accurate prediction to happen, it is necessary to access a user's view history and preferences. Otherwise, prefetching will be more of a waste to bandwidth than a benefit. After learning the user’s viewing history and opinions on popular content, it is easier to predict the next video to prefetch, but this data is valuable and possibly sensitive. [ 18 ] There has been research on applying differential privacy to video prefetching, to improve user privacy. [ 18 ]
E-commerce has been growing rapidly, so there have been initiatives to reduce consumer perceptions of risk while shopping online. Firms have found ways to gain trust from new consumers through the use of seals and certifications off of third-party platforms. A study done by Electronic Commerce Research found that payment providers can reduce perceptions of risk from consumers by having third-party logos and seals on the checkout page to enhance visitor conversion. [ 19 ] These logos and certificates serve as an indicator for the consumer, so they feel safe about inputting their payment information and shipping address to an otherwise unknown or untrusted website.
mIPS - mobile Intrusion Prevention System looks to be location-aware and help protect users when utilizing future technology such as virtualized environments where the phone acts as a small virtual machine. Some cases to be wary about in the future includes stalking attacks, bandwidth stealing, attack on cloud hosts, and PA2: traffic analysis attack on the 5G device based on a confined area. Current privacy protection programs are prone to leakage and do not account for the changing of Bluetooth, locations, and LAN connections which affect how often leakage can occur. [ 20 ]
In the context of sensor net , public-key based access control (PKC) may be a good solution in the future to cover some issues in wireless access control. For sensor net, the danger from attackers includes; impersonation which grants access to malicious users, replay attack where the adversary captures sensitive information by replaying it, interleaving which selectively combines messages from previous sessions, reflection where an adversary sends an identical message to the originator similar to impersonation, forced delay which blocks communication message to be sent at a later time, and chosen-text attack where the attacker tries to extract the keys to access the sensor. The solution to this may be public key-based cryptography as a study done by Haodong Wang shows that PKC-based protocol presented is better than the traditional symmetric key in regards to memory usage, message complexity, and security resilience. [ 21 ]
Privacy management is a big part of social networks and this paper presents several solutions to this issue. For example, users of various social networks has the ability to control and specify what information they want to share to certain people based on their trust levels. Privacy concerns arise from this, for example in 2007 Facebook received complaints about their advertisements. In this instance Facebook’s partner collects information about a user and spreads it to the user’s friends without any consent. There are some proposed solutions in prototype stage by using a protocol that focuses on cryptographic and digital signature techniques to ensure the right privacy protections are in place. [ 22 ]
With increasing data collection one source may have they become prone to privacy violations and a target for malicious attacks due to the abundance of personal information they hold. [ 23 ] Some solutions proposed would be to anonymize the data by building a virtual database while that anonymizes both the data provider and the subjects of the data. The proposed solution here is a new and developing technology called l-site diversity. [ 24 ] | https://en.wikipedia.org/wiki/Soft_privacy_technologies |
A soft story building is a multi-story building in which one or more floors have windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall would normally be required for stability as a matter of earthquake engineering design. [ 1 ] [ 2 ] A typical soft story building is an apartment building of three or more stories located over a ground level with large openings, such as a parking garage or series of retail businesses with large windows. [ 3 ]
Buildings are classified as having a soft story if that level is less than 70% as stiff as the floor immediately above it, or less than 80% as stiff as the average stiffness of the three floors above it. [ 4 ] Soft story buildings are vulnerable to collapse in a moderate to severe earthquake in a phenomenon known as soft story collapse . [ 5 ] The inadequately-braced level is relatively less resistant than surrounding floors to lateral earthquake motion, so a disproportionate amount of the building's overall side-to-side drift is focused on that floor. Subject to disproportionate lateral stress, and less able to withstand the stress, the floor becomes a weak point that may suffer structural damage or complete failure, which in turn results in the collapse of the entire building. [ 4 ]
Soft-story failure was responsible for nearly half of all homes that became uninhabitable in California's Loma Prieta earthquake of 1989 and was projected to cause severe damage and possible destruction of 160,000 homes in the event of a more significant earthquake in the San Francisco Bay Area . [ 6 ] As of 2009, few such buildings in the area had undergone the relatively inexpensive seismic retrofit to correct the condition. [ 1 ] [ 7 ] In 2013, San Francisco mandated screening of soft-story buildings to determine if retrofitting is necessary and required that retrofitting be completed by 2017 through 2020. [ 8 ]
After the establishment of the San Francisco Mandatory Seismic Retrofit Program in 2013, [ 9 ] Los Angeles adopted a similar ordinance targeting soft-story apartment buildings. [ 10 ] This ordinance is to reduce structural damage in the event of an earthquake by reinforcing soft-story areas with steel structures. A soft-story building is described as existing wood-frame buildings with soft, weak, or open-front walls and existing non-ductile concrete buildings in the ordinance. Most of these buildings were built before 1978, before building codes were changed. [ citation needed ]
Los Angeles property owners are being targeted by the size of their buildings. The first group of ordinances went out May 2, 2016, with sixteen or more units and more than three stories. The second is July 22, 2016, with sixteen or more units and two stories. The third is October 17, 2016, with sixteen or fewer units and more than three stories. The fourth is January 30, 2017, for nine to fifteen units. The fifth is May 29, 2017 for seven to eight units. The sixth is August 14, 2017, for four to six units. Then on October 30, 2017 condominiums and commercial buildings will receive their orders to comply.
The order to comply is legally and logistically significant because it starts a "ticking clock".
In Los Angeles, property owners have two years from the date of the order to bring forth approved plans. After that milestone, they have 3.5 years (counting from when the order was received) to obtain the construction permit. Total completion, as confirmed by receiving a certificate of compliance, must be attained within seven years of the date of issue of the original order.
In Los Angeles, property owners also have the option to demolish their noncompliant buildings. Demolition plans must be submitted within two years, and a demolition permit must be issued within 3.5 years (from the date of the original compliance order), and the actual demolition must be completed within seven years of the original compliance order. [ citation needed ]
Failure to meet the deadlines can result in the municipality stepping in, evicting any lingering tenants, and then demolishing the building, whereupon the cost of demolition is charged back to the property owner. If the property owner refuses to pay the bill, then the City can seize the entire property and sell it in order to pay for the demolition (including all associated clean-up tasks), as well as any back-taxes that may be owing. However, because land values are often high, it is rare for property owners to neglect orders from the municipality.
In Turkey, multi-story residential buildings often have a soft inset ground floor, which is used in high-density areas in Asia to provide extra space for parking or pedestrians. About 90% of buildings that collapsed in the 1999 İzmit earthquake in Turkey had soft stories, which prompted the creation of a building code for earthquake safety. [ 11 ] [ 12 ] In 2016, Turkish President Recep Tayyip Erdoğan started issuing amnesty to developers for building regulations, [ 13 ] allowing the construction of unsafe multi-story buildings, including ones with soft stories. [ 14 ] [ 11 ] The 2023 Turkey–Syria earthquake destroyed many soft-story buildings, which were widespread in the country and greatly increased the amount of damage and number of casualties. [ 13 ] | https://en.wikipedia.org/wiki/Soft_story_building |
In physics and astronomy , an N -body simulation is a simulation of a dynamical system of particles, usually under the influence of physical forces, such as gravity (see n -body problem for other applications). N -body simulations are widely used tools in astrophysics , from investigating the dynamics of few-body systems like the Earth - Moon - Sun system to understanding the evolution of the large-scale structure of the universe . [ 1 ] In physical cosmology , N -body simulations are used to study processes of non-linear structure formation such as galaxy filaments and galaxy halos from the influence of dark matter . Direct N -body simulations are used to study the dynamical evolution of star clusters .
The 'particles' treated by the simulation may or may not correspond to physical objects which are particulate in nature. For example, an N-body simulation of a star cluster might have a particle per star, so each particle has some physical significance. On the other hand, a simulation of a gas cloud cannot afford to have a particle for each atom or molecule of gas as this would require on the order of 10 23 particles for each mole of material (see Avogadro constant ), so a single 'particle' would represent some much larger quantity of gas (often implemented using Smoothed Particle Hydrodynamics ). This quantity need not have any physical significance, but must be chosen as a compromise between accuracy and manageable computer requirements.
Dark matter plays an important role in the formation of galaxies. The time evolution of the density f (in phase space) of dark matter particles, can be described by the collisionless Boltzmann equation
d f d t = ∂ f ∂ t + v ⋅ ∇ f − ∂ f ∂ v ⋅ ∇ Φ {\displaystyle {\frac {df}{dt}}={\frac {\partial f}{\partial t}}+\mathbf {v} \cdot \nabla f-{\frac {\partial f}{\partial \mathbf {v} }}\cdot \nabla \Phi }
In the equation, v {\displaystyle \mathbf {v} } is the velocity, and Φ is the gravitational potential given by Poisson's Equation . These two coupled equations are solved in an expanding background Universe, which is governed by the Friedmann equations , after determining the initial conditions of dark matter particles. The conventional method employed for initializing positions and velocities of dark matter particles involves moving particles within a uniform Cartesian lattice or a glass-like particle configuration. [ 2 ] This is done by using a linear theory approximation or a low-order perturbation theory . [ 3 ]
In direct gravitational N -body simulations, the equations of motion of a system of N particles under the influence of their mutual gravitational forces are integrated numerically without any simplifying approximations. These calculations are used in situations where interactions between individual objects, such as stars or planets, are important to the evolution of the system.
The first direct gravitational N -body simulations were carried out by Erik Holmberg at the Lund Observatory in 1941, determining the forces between stars in encountering galaxies via the mathematical equivalence between light propagation and gravitational interaction: putting light bulbs at the positions of the stars and measuring the directional light fluxes at the positions of the stars by a photo cell, the equations of motion can be integrated with O ( N ) {\displaystyle O(N)} effort. [ 4 ] The first purely calculational simulations were then done by Sebastian von Hoerner at the Astronomisches Rechen-Institut in Heidelberg , Germany. Sverre Aarseth at the University of Cambridge (UK) dedicated his entire scientific life to the development of a series of highly efficient N -body codes for astrophysical applications which use adaptive (hierarchical) time steps, an Ahmad-Cohen neighbour scheme and regularization of close encounters. Regularization is a mathematical trick to remove the singularity in the Newtonian law of gravitation for two particles which approach each other arbitrarily close. Sverre Aarseth's codes are used to study the dynamics of star clusters, planetary systems and galactic nuclei. [ citation needed ]
Many simulations are large enough that the effects of general relativity in establishing a Friedmann-Lemaitre-Robertson-Walker cosmology are significant. This is incorporated in the simulation as an evolving measure of distance (or scale factor ) in a comoving coordinate system, which causes the particles to slow in comoving coordinates (as well as due to the redshifting of their physical energy). However, the contributions of general relativity and the finite speed of gravity can otherwise be ignored, as typical dynamical timescales are long compared to the light crossing time for the simulation, and the space-time curvature induced by the particles and the particle velocities are small. The boundary conditions of these cosmological simulations are usually periodic (or toroidal), so that one edge of the simulation volume matches up with the opposite edge.
N -body simulations are simple in principle, because they involve merely integrating the 6 N ordinary differential equations defining the particle motions in Newtonian gravity . In practice, the number N of particles involved is usually very large (typical simulations include many millions, the Millennium simulation included ten billion) and the number of particle-particle interactions needing to be computed increases on the order of N 2 , and so direct integration of the differential equations can be prohibitively computationally expensive. Therefore, a number of refinements are commonly used.
Numerical integration is usually performed over small timesteps using a method such as leapfrog integration . However all numerical integration leads to errors. Smaller steps give lower errors but run more slowly. Leapfrog integration is roughly 2nd order on the timestep, other integrators such as Runge–Kutta methods can have 4th order accuracy or much higher.
One of the simplest refinements is that each particle carries with it its own timestep variable, so that particles with widely different dynamical times don't all have to be evolved forward at the rate of that with the shortest time.
There are two basic approximation schemes to decrease the computational time for such simulations. These can reduce the computational complexity to O(N log N) or better, at the loss of accuracy.
In tree methods , such as a Barnes–Hut simulation , an octree is usually used to divide the volume into cubic cells and only interactions between particles from nearby cells need to be treated individually; particles in distant cells can be treated collectively as a single large particle centered at the distant cell's center of mass (or as a low-order multipole expansion). This can dramatically reduce the number of particle pair interactions that must be computed. To prevent the simulation from becoming swamped by computing particle-particle interactions, the cells must be refined to smaller cells in denser parts of the simulation which contain many particles per cell. For simulations where particles are not evenly distributed, the well-separated pair decomposition methods of Callahan and Kosaraju yield optimal O( n log n ) time per iteration with fixed dimension.
Another possibility is the particle mesh method in which space is discretised on a mesh and, for the purposes of computing the gravitational potential , particles are assumed to be divided between the surrounding 2x2 vertices of the mesh. The potential energy Φ can be found with the Poisson equation
∇ 2 Φ = 4 π G ρ , {\displaystyle \nabla ^{2}\Phi =4\pi G{\rho },\,}
where G is Newton's constant and ρ {\displaystyle \rho } is the density (number of particles at the mesh points). The fast Fourier transform can solve this efficiently by going to the frequency domain where the Poisson equation has the simple form
Φ ^ = − 4 π G ρ ^ k 2 , {\displaystyle {\hat {\Phi }}=-4\pi G{\frac {\hat {\rho }}{k^{2}}},}
where k → {\displaystyle {\vec {k}}} is the comoving wavenumber and the hats denote Fourier transforms. Since g → = − ∇ → Φ {\displaystyle {\vec {g}}=-{\vec {\nabla }}\Phi } , the gravitational field can now be found by multiplying by − i k → {\displaystyle -i{\vec {k}}} and computing the inverse Fourier transform (or computing the inverse transform and then using some other method). Since this method is limited by the mesh size, in practice a smaller mesh or some other technique (such as combining with a tree or simple particle-particle algorithm) is used to compute the small-scale forces. Sometimes an adaptive mesh is used, in which the mesh cells are much smaller in the denser regions of the simulation.
Several different gravitational perturbation algorithms are used to get fairly accurate estimates of the path of objects in the Solar System .
People often decide to put a satellite in a frozen orbit .
The path of a satellite closely orbiting the Earth can be accurately modeled starting from the 2-body elliptical orbit around the center of the Earth, and adding small corrections due to the oblateness of the Earth , gravitational attraction of the Sun and Moon, atmospheric drag, etc.
It is possible to find a frozen orbit without calculating the actual path of the satellite.
The path of a small planet, comet, or long-range spacecraft can often be accurately modeled starting from the 2-body elliptical orbit around the Sun, and adding small corrections from the gravitational attraction of the larger planets in their known orbits.
Some characteristics of the long-term paths of a system of particles can be calculated directly. The actual path of any particular particle does not need to be calculated as an intermediate step. Such characteristics include Lyapunov stability , Lyapunov time , various measurements from ergodic theory , etc.
Although there are millions or billions of particles in typical simulations, they typically correspond to a real particle with a very large mass, typically 10 9 solar masses . This can introduce problems with short-range interactions between the particles such as the formation of two-particle binary systems. As the particles are meant to represent large numbers of dark matter particles or groups of stars, these binaries are unphysical. To prevent this, a softened Newtonian force law is used, which does not diverge as the inverse-square radius at short distances. Most simulations implement this quite naturally by running the simulations on cells of finite size. It is important to implement the discretization procedure in such a way that particles always exert a vanishing force on themselves.
Softening is a numerical trick used in N-body techniques to prevent numerical divergences when a particle comes too close to another (and the force goes to infinity). This is obtained by modifying the regularized gravitational potential of each particle as
Φ = − 1 r 2 + ϵ 2 , {\displaystyle \Phi =-{\frac {1}{\sqrt {r^{2}+\epsilon ^{2}}}},}
(rather than 1/r) where ϵ {\displaystyle \epsilon } is the softening parameter. The value of the softening parameter should be set small enough to keep simulations realistic.
N -body simulations give findings on the large-scale dark matter distribution and the structure of dark matter halos. According to simulations of cold dark matter, the overall distribution of dark matter on a large scale is not entirely uniform. Instead, it displays a structure resembling a network, consisting of voids, walls, filaments, and halos. Also, simulations show that the relationship between the concentration of halos and factors such as mass, initial fluctuation spectrum, and cosmological parameters is linked to the actual formation time of the halos. [ 5 ] In particular, halos with lower mass tend to form earlier, and as a result, have higher concentrations due to the higher density of the Universe at the time of their formation. Shapes of halos are found to deviate from being perfectly spherical. Typically, halos are found to be elongated and become increasingly prolate towards their centers. However, interactions between dark matter and baryons would affect the internal structure of dark matter halos. Simulations that model both dark matters and baryons are needed to study small-scale structures.
Many simulations simulate only cold dark matter , and thus include only the gravitational force. Incorporating baryons , leptons and photons into the simulations dramatically increases their complexity and often radical simplifications of the underlying physics must be made. However, this is an extremely important area and many modern simulations are now trying to understand processes that occur during galaxy formation which could account for galaxy bias .
Reif and Tate [ 6 ] prove that if the n -body reachability problem is defined as follows – given n bodies satisfying a fixed electrostatic potential law, determining if a body reaches a destination ball in a given time bound where we require a poly( n ) bits of accuracy and the target time is poly( n ) is in PSPACE .
On the other hand, if the question is whether the body eventually reaches the destination ball, the problem is PSPACE-hard. These bounds are based on similar complexity bounds obtained for ray tracing .
The simplest implementation of N-body simulations where n ≥ 3 {\textstyle n\geq 3} is a naive propagation of orbiting bodies; naive implying that the only forces acting on the orbiting bodies is the gravitational force which they exert on each other. In object-oriented programming languages, such as C++ , some boilerplate code is useful for establishing the fundamental mathematical structures as well as data containers required for propagation; namely state vectors , and thus vectors , and some fundamental object containing this data, as well as the mass of an orbiting body. This method is applicable to other types of N-body simulations as well; a simulation of point masses with charges would use a similar method, however the force would be due to attraction or repulsion by interaction of electric fields. Regardless, acceleration of particle is a result of summed force vectors, divided by the mass of the particle:
a → = 1 m ∑ F → {\displaystyle {\vec {a}}={\frac {1}{m}}\sum {\vec {F}}}
An example of a programmatically stable and scalable method for containing kinematic data for a particle is the use of fixed length arrays, which in optimised code allows for easy memory allocation and prediction of consumed resources; as seen in the following C++ code:
Note that OrbitalEntity contains enough room for a state vector, where:
Additionally, OrbitalEntity contains enough room for a mass value.
Commonly, N-body simulations will be systems based on some type of equations of motion ; of these, most will be dependent on some initial configuration to "seed" the simulation. In systems such as those dependent on some gravitational or electric potential, the force on a simulation entity is independent on its velocity. Hence, to seed the forces of the simulation, merely initial positions are needed, but this will not allow propagation- initial velocities are required. Consider a planet orbiting a star- it has no motion, but is subject to gravitational attraction to its host star. As a time progresses, and time steps are added, it will gather velocity according to its acceleration. For a given instant in time, t n {\displaystyle t_{n}} , the resultant acceleration of a body due to its neighbouring masses is independent of its velocity, however, for the time step t n + 1 {\displaystyle t_{n+1}} , the resulting change in position is significantly different due the propagation's inherent dependency on velocity. In basic propagation mechanisms, such as the symplectic euler method to be used below, the position of an object at t n + 1 {\displaystyle t_{n+1}} is only dependent on its velocity at t n {\displaystyle t_{n}} , as the shift in position is calculated via
r → t n + 1 = r → t n + v → t n ⋅ Δ t {\displaystyle {\vec {r}}_{t_{n+1}}={\vec {r}}_{t_{n}}+{\vec {v}}_{t_{n}}\cdot \Delta t}
Without acceleration, v → t n {\textstyle {\vec {v}}_{t_{n}}} is static, however, from the perspective of an observer seeing only position, it will take two time steps to see a change in velocity.
A solar-system-like simulation can be accomplished by taking average distances of planet equivalent point masses from a central star. To keep code simple, a non-rigorous approach based on semi-major axes and mean velocities will be used. Memory space for these bodies must be reserved before the bodies are configured; to allow for scalability, a malloc command may be used:
where N_ASTEROIDS is a variable which will remain at 0 temporarily, but allows for future inclusion of significant numbers of asteroids, at the users discretion. A critical step for the configuration of simulations is to establish the time ranges of the simulation, t 0 {\displaystyle t_{0}} to t end {\displaystyle t_{\text{end}}} , as well as the incremental time step d t {\displaystyle dt} which will progress the simulation forward:
The positions and velocities established above are interpreted to be correct for t = t 0 {\displaystyle t=t_{0}} .
The extent of a simulation would logically be for the period where t 0 ≤ t < t end {\displaystyle t_{0}\leq t<t_{\text{end}}} .
An entire simulation can consist of hundreds, thousands, millions, billions, or sometimes trillions of time steps. At the elementary level, each time step (for simulations with particles moving due to forces exerted on them) involves
The above can be implemented quite simply with a while loop which continues while t {\displaystyle t} exists in the aforementioned range:
Focusing on the inner four rocky planets in the simulation, the trajectories resulting from the above propagation is shown below: | https://en.wikipedia.org/wiki/Softening |
The softening point is the temperature at which a material softens beyond some arbitrary softness. [ 1 ] It can be determined, for example, by the Vicat method (ASTM-D1525 or ISO 306), Heat Deflection Test (ASTM-D648) or a ring and ball method (ISO 4625 or ASTM E28-67/E28-99 or ASTM D36 or ASTM D6493 - 11 or JIS K 6863). A ring and ball apparatus can also be used for the determination of softening point of bituminous materials. [ 2 ]
This thermodynamics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Softening_point |
Software-defined data center ( SDDC ; also: virtual data center, VDC) is a marketing term that extends virtualization concepts such as abstraction, pooling, and automation to all data center resources and services to achieve IT as a service (ITaaS). [ 1 ] In a software-defined data center, "all elements of the infrastructure — networking, storage, CPU and security – are virtualized and delivered as a service." [ 2 ]
SDDC support can be claimed by a wide variety of approaches. Critics see the software-defined data center as a marketing tool and "software-defined hype," noting this variability. [ 3 ]
In 2013, analysts were divided into three different groups, [ 3 ] those who think it is "just another software-defined hype", those who think most of the components are already available and those who see a potential future market. There was no unified agreement about the direction of SDDC. For some areas like the software-defined networking a market value of about US$3.7 billion by 2016 was expected, compared to US$360 million in 2013. [ 3 ] (software-defined networking was expected to reach US$18.5 billion in 2022 [ 4 ] ) IDC estimates that the software-defined storage market is poised to expand faster than any other storage market. [ 3 ]
The software-defined data center encompasses a variety of concepts and data-center infrastructure components, with each component potentially provisioned , operated, and managed through an application programming interface (API). [ 5 ] Core architectural components that comprise the software-defined data center [ 6 ] include the following:
A software-defined data center differs from a private cloud , since a private cloud only has to offer virtual-machine self-service, [ 9 ] beneath which it could use traditional provisioning and management. Instead, SDDC concepts imagine a data center that can encompass private, public, and hybrid clouds. [ 10 ]
Data centers traditionally lacked the capacity to accommodate total virtualization. [ 11 ] By 2013, companies began laying the foundation for software-defined data centers with virtualization. [ 3 ] Ben Cherian of Midokura considered Amazon Web Services as a catalyst for the move toward software-defined data centers because it "convinced the world that the data center could be abstracted into much smaller units and could be treated as disposable pieces of technology, which in turn could be priced as a utility." [ 5 ]
In 2013, the software-defined data center term was promoted as a paradigm shift. [ 5 ] [ 12 ] According to Steve Herrod, the promise of the software-defined data center was that companies would no longer need to rely on specialized hardware or hire consultants to install and program hardware in its specialized language. [ 13 ] Rather, IT would define applications and all of the resources they require—including compute, storage, networking, security, and availability—and group all of the required components to create a “logical application.” [ 13 ]
Commonly cited benefits of software-defined data centers include improved efficiency [ 14 ] from extending virtualization throughout the data center; increased agility [ 15 ] from provisioning applications quickly; improved control [ 15 ] over application availability and security through policy-based governance; and the flexibility [ 14 ] [ 15 ] to run new and existing applications in multiple platforms and clouds.
In addition, a software-defined data center implementation could reduce a company's energy usage by enabling servers and other data center hardware to run at decreased power levels or be turned off. [ 15 ] Some believe that software-defined data centers improve security by giving organizations more control over their hosted data and security levels, compared to security provided by hosted-cloud providers. [ 15 ]
The software-defined data center was marketed to drive down prices for data center hardware and challenge traditional hardware vendors to develop new ways to differentiate their products through software and services. [ 16 ]
The concepts of software-defined in general, and software-defined data centers in particular, have been dismissed by some as “nonsense,” “ marketecture ,” and “software-defined hype.” [ 3 ] Some critics believe that only a minority of companies with “completely homogeneous IT systems’” already in place, such as Yahoo! and Google , can transition to software-defined data centers. [ 3 ]
According to some observers, software-defined data centers won’t necessarily eliminate challenges that relate to handling the differences between development and production environments; managing a mix of legacy and new applications; or delivering service-level agreements (SLAs). [ 3 ]
Software-defined networking was seen as essential to the software-defined data center, but it is also considered to be the “least mature technology” required to enable the software-defined data center. [ 11 ] However, several companies, including Arista Networks , Cisco , Microsoft and VMware , market products to enable virtual networks that are provisioned, extended, and moved across existing physical networks. [ 11 ]
Several competing network virtualization standards already existed by 2012. [ 11 ] Neutron, the networking component of the open-source software OpenStack project, provides an application-level abstraction of network resources and includes an interface for configuring virtual switches. [ 11 ] [ 17 ]
The software-defined data center approach will force IT organizations to adapt. Software-defined environments require rethinking many IT processes—including automation, metering, and billing—and executing service delivery, service activation, and service assurance. [ 15 ] A widespread transition to the SDDC could take years. [ 6 ] | https://en.wikipedia.org/wiki/Software-defined_data_center |
Software-defined mobile networking ( SDMN ) is an approach to the design of mobile networks where all protocol-specific features are implemented in software, maximizing the use of generic and commodity hardware and software in both the core network and radio access network (RAN).
Through the 20th century, telecommunications technology was driven by hardware development, with most functions implemented in special-purpose equipment.
In the early 2000s, generally available CPUs became cheap enough to enable commercial software-defined radio (SDR) technology and softswitches .
SDMN extends these trends into the design of mobile networks, moving nearly all network functions into software.
The term "software-defined mobile network" first appeared in public literature in early 2014, used independently by Lime Microsystems [ 1 ] [ 2 ] and researchers from University of Oulu , Finland. [ 3 ]
Mobile networks based on special-purpose hardware suffer from the following limitations:
SDR is an important element of SDMN, because it replaces protocol-specific radio hardware with protocol-agnostic digital transceivers.
While many earlier digital radio systems used field-programmable gate arrays (FPGAs) or special-purposed digital signal processors (DSPs) for calculations on baseband radio waveforms, the SDMN approach moves all of the baseband processing into general-purpose CPUs .
SDMN radio systems also use hardware with publicly-documented interfaces that is designed to be readily reproducible by multiple manufacturers.
SDMN designs avoid the use of components that are specialized as to their functions or that are available from only a single vendor.
This is true of both the hardware and software elements of the network.
The telephony switches of SDMN networks are software-based, including software transcoding for speech codecs.
A new SDN architecture for wireless distribution systems (WDSs) is explored that eliminates the need for multi-hop flooding of route information and therefore enables WDNs to easily expand. [ 4 ] The key idea is to split network control and data forwarding by using two separate frequency bands. The forwarding nodes and the SDN controller exchange link-state information and other network control signaling in one of the bands, while actual data forwarding takes place in the other band.
The SDMN approach has many advantages over hardware-based mobile network designs. | https://en.wikipedia.org/wiki/Software-defined_mobile_network |
Software-defined storage ( SDS ) is a marketing term for computer data storage software for policy-based provisioning and management of data storage independent of the underlying hardware. Software-defined storage typically includes a form of storage virtualization to separate the storage hardware from the software that manages it. [ 1 ] The software enabling a software-defined storage environment may also provide policy management for features such as data deduplication , replication, thin provisioning , snapshots, copy-on-write clones, tiering and backup.
Software-defined storage (SDS) hardware may or may not also have abstraction, pooling, or automation software of its own. When implemented as software only in conjunction with commodity servers with internal disks, it may suggest software such as a virtual or global file system or distributed block storage . If it is software layered over sophisticated large storage arrays, it suggests software such as storage virtualization or storage resource management , categories of products that address separate and different problems. If the policy and management functions also include a form of artificial intelligence to automate protection and recovery, it can be considered as intelligent abstraction. [ 2 ] Software-defined storage may be implemented via appliances over a traditional storage area network (SAN), or implemented as network-attached storage (NAS), or using object-based storage . In March 2014 the Storage Networking Industry Association (SNIA) began a report on software-defined storage. [ 3 ]
VMware used the marketing term " software-defined data center " (SDDC) for a broader concept wherein all the virtual storage, server, networking and security resources required by an application can be defined by software and provisioned automatically. [ 4 ] [ 5 ] Other smaller companies then adopted the term "software-defined storage", such as Cleversafe (acquired by IBM ), and OpenIO .
Based on similar concepts as software-defined networking (SDN), [ 6 ] interest in SDS rose after VMware acquired Nicira for over a billion dollars in 2012.
Data storage vendors used various definitions for software-defined storage depending on their product-line. Storage Networking Industry Association (SNIA), a standards group, attempted a multi-vendor, negotiated definition with examples. [ 7 ]
The software-defined storage industry is projected to reach $86 billion by 2023. [ 8 ]
Building on the concept of VMware, esurfing cloud has launched a new software-defined storage product called HBlock. HBlock is a lightweight storage cluster controller that operates in user mode. It can be installed on any Linux operating system as a regular application without root access, and deployed alongside other applications on the server. HBlock integrates unused disk space across various servers to create high-performance and highly available virtual disks. These virtual disks can be mounted to local or other remote servers using the standard iSCSI protocol, revitalizing storage resources on-site without impacting existing operations or requiring additional hardware purchases. [ 9 ]
Characteristics of software-defined storage may include the following features: [ 10 ]
In computing , a storage hypervisor is a software program which can run on a physical server hardware platform, on a virtual machine , inside a hypervisor OS or in the storage network. It may co-reside with virtual machine supervisors or have exclusive control of its platform. Similar to virtual server hypervisors a storage hypervisor may run on a specific hardware platform, a specific hardware architecture, or be hardware independent. [ 11 ]
The storage hypervisor software virtualizes the individual storage resources it controls and creates one or more flexible pools of storage capacity. In this way it separates the direct link between physical and logical resources in parallel to virtual server hypervisors. By moving storage management into isolated layer it also helps to increase system uptime and High Availability . "Similarly, a storage hypervisor can be used to manage virtualized storage resources to increase utilization rates of disk while maintaining high reliability." [ 12 ]
The storage hypervisor, a centrally-managed supervisory software program, provides a comprehensive set of storage control and monitoring functions that operate as a transparent virtual layer across consolidated disk pools to improve their availability , speed and utilization.
Storage hypervisors enhance the combined value of multiple disk storage systems, including dissimilar and incompatible models, by supplementing their individual capabilities with extended provisioning, data protection, replication and performance acceleration services.
In contrast to embedded software or disk controller firmware confined to a packaged storage system or appliance, the storage hypervisor and its functionality spans different models and brands and types of storage [including SSD ( solid state disks ), SAN ( storage area network ) and DAS ( direct attached storage ) and Unified Storage(SAN and NAS)] covering a wide range of price and performance characteristics or tiers. The underlying devices need not be explicitly integrated with each other nor bundled together.
A storage hypervisor enables hardware interchangeability. The storage hardware underlying a storage hypervisor matters only in a generic way with regard to performance and capacity. While underlying "features" may be passed through the hypervisor, the benefits of a storage hypervisor underline its ability to present uniform virtual devices and services from dissimilar and incompatible hardware, thus making these devices interchangeable. Continuous replacement and substitution of the underlying physical storage may take place, without altering or interrupting the virtual storage environment that is presented.
The storage hypervisor manages, virtualizes and controls all storage resources, allocating and providing the needed attributes (performance, availability) and services (automated provisioning , snapshots , replication ), either directly or over a storage network, as required to serve the needs of each individual environment.
The term "hypervisor" within "storage hypervisor" is so named because it goes beyond a supervisor, [ 13 ] it is conceptually a level higher than a supervisor and therefore acts as the next higher level of management and intelligence that sits above and spans its control over device-level storage controllers, disk arrays, and virtualization middleware.
A storage hypervisor has also been defined as a higher level of storage virtualization [ 14 ] software, providing a "Consolidation and cost: Storage pooling increases utilization and decreases costs. Business availability: Data mobility of virtual volumes can improve availability. Application support: Tiered storage optimization aligns storage costs with required application service levels". [ 15 ] The term has also been used in reference to use cases including its reference to its role with storage virtualization in disaster recovery [ 16 ] and, in a more limited way, defined as a volume migration capability across SANs. [ 17 ]
An analogy can be drawn between the concept of a server hypervisor and the concept of a storage hypervisor. By virtualizing servers, server hypervisors ( VMware ESX , Microsoft Hyper-V , Citrix Hypervisor, Linux KVM , Xen , z/VM ) increased the utilization rates for server resources, and provided management flexibility by de-coupling servers from hardware. This led to cost savings in server infrastructure since fewer physical servers were needed to handle the same workload, and provided flexibility in administrative operations like backup, failover and disaster recovery.
A storage hypervisor does for storage resources what the server hypervisor did for server resources. A storage hypervisor changes how the server hypervisor handles storage I/O to get more performance out of existing storage resources, and increases efficiency in storage capacity consumption, storage provisioning and snapshot/clone technology. A storage hypervisor, like a server hypervisor, increases performance and management flexibility for improved resource utilization. | https://en.wikipedia.org/wiki/Software-defined_storage |
Software Component Management Object ( SCOMO ) is an Open Mobile Alliance specification that allows a management authority to perform mobile device management on a remote device, including installation, uninstallation, activation and deactivation of software components over the air. [ 1 ] It appears to have been in use between 2008 [ 2 ] [ 3 ] and 2013. [ 4 ]
This computing article is a stub . You can help Wikipedia by expanding it .
This article about wireless technology is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Software_Component_Management_Object |
System Package Data Exchange ( SPDX , formerly Software Package Data Exchange ) is an open standard capable of representing systems with digital components as bills of materials (BOMs). [ 1 ] First designed to describe software components, SPDX can describe the components of software systems, AI models, software builds, security data, and other data packages. SPDX allows the expression of components, licenses , copyrights, security references and other metadata relating to systems. [ 2 ]
The original purpose of SPDX was to improve license compliance, [ 3 ] and it has since been expanded to facilitate additional use cases such as supply-chain transparency and security. [ 4 ] SPDX is authored by the community-driven SPDX Project involving key industry experts, organizations, and open-source enthusiasts under the auspices of the Linux Foundation .
The SPDX specification is recognized as the international open standard for security, license compliance, and other software supply chain artifacts as ISO/IEC 5962:2021. The current [ when? ] version of the standard is 3.0. [ 5 ]
The SPDX 2.x standard defines an SBOM document, which contains SPDX metadata about software. The document itself can be expressed in multiple formats, including JSON, YAML, RDF/XML, tag–value, and spreadsheet. Each SPDX document describes one or more elements, which can be a software package, a specific file, or a snippet from a file. Each element is given a unique identifier, and metadata for an element can refer to other elements. [ 6 ]
SPDX 3.0 allows users to communicate information at a much more granular level without having to package it as "envelope" data. A key design principle in SPDX 3.0 is that all elements may be expressed and referenced independent of any other element. This independence is required to support a variety of content exchange and analysis use cases and makes it easier to communicate single elements of interest. The relationship structure has also been updated to be both more expressive and easier to understand compared to older versions of the spec.
The SPDX 3.0 data model is based on the Resource Description Framework (RDF). Data may be serialized in a variety of formats for storage and transmission, including formats defined in RDF 1.1 such as JSON-LD, Turtle (Terse RDF Triple Language), N-Triples, and RDF/XML.
The 3.0 specification introduced profiles to support the expansion of use cases beyond software, without increasing overall complexity. Profiles allow users to define data for the use cases they need, while also increasing the amount of information that can be gathered directly from the SPDX data. There are eight profiles defined by SPDX 3.0:
The first version of the SPDX specification was intended to make compliance with software licenses easier, [ 3 ] but subsequent versions of the specification added capabilities intended for other use-cases, such as being able to contain references to known software vulnerabilities . [ 13 ] Recent versions of SPDX fulfill the NTIA's 'Minimum Elements For a Software Bill of Materials'. [ 17 ]
SPDX 2.2.1 was submitted to the International Organization for Standardization (ISO) in October, 2020, and was published as ISO/IEC 5962:2021 Information technology — SPDX® Specification V2.2.1 in August, 2021. [ 10 ] [ 18 ]
Each license is identified by a full name, such as "Mozilla Public License 2.0" and a short identifier, here "MPL-2.0".
Licenses can be combined by operators AND and OR , and grouping ( , ) .
For example, (Apache-2.0 OR MIT) means that one can choose between Apache-2.0 ( Apache License ) or MIT ( MIT license ). On the other hand, (Apache-2.0 AND MIT) means that both licenses apply.
There is also a "+" operator which, when applied to a license, means that future versions of the license apply as well. For example, Apache-1.1+ means that Apache-1.1 and Apache-2.0 may apply (and future versions if any).
SPDX describes the exact terms under which a piece of software is licensed. It does not attempt to categorize licenses by type, for instance by describing licenses with similar terms to the BSD License as "BSD-like". [ 19 ]
In 2020, the European Commission published its Joinup Licensing Assistant, [ 20 ] which makes possible the selection and comparison of more than 50 licenses, with access to their SPDX identifier and full text.
The GNU family of licenses (e.g., GNU General Public License version 2 ) have the choice of choosing a later version of the license built in. Sometimes, it was not clear whether the SPDX expression GPL-2.0 meant "exactly GPL version 2.0" or "GPL version 2.0 or any later version". [ 21 ] Thus, since version 3.0 of the SPDX License List, the GNU family of licenses got new names. [ 22 ] GPL-2.0-only means "exactly version 2.0" and GPL-2.0-or-later means "version 2.0 or any later version".
The SPDX license identifier can be added to the top of source code files as a short string unambiguously declaring the license used. The SPDX-License-Identifier syntax, pioneered by Das U-Boot in 2013, became part of SPDX in version 2.1. In 2017, the FSFE launched REUSE, which provides tools to validate the comment and to efficiently extract copyright information. [ 23 ]
The SPDX license identifier is also used in a number of package managers such as npm , [ 24 ] Python, [ 25 ] and Rust cargo. [ 26 ] SPDX license expressions are used in RPM package metadata in Fedora Linux , replacing the earlier use of the Callaway system. [ 27 ] Debian uses a slightly different license specification. [ 28 ] | https://en.wikipedia.org/wiki/Software_Package_Data_Exchange |
In computing, adoption means the transfer (conversion) between an old system and a target system in an organization (or more broadly, by anyone).
If a company works with an old software system, it may want to use a new system which is more efficient, has more work capacity, etc. So then a new system needs to be adopted, after which it can be used by users.
There are several adoption strategies that can be used to implement a system in an organization. The main strategies are big bang adoption , parallel adoption and phased adoption . "Big bang" is a metaphor for the cosmological theory of the same name , in which the start of the cosmos happened at one moment in time. This is also the case with the big bang adoption approach, in which the new system is supposed to be adopted wholesale on one date. In the case of parallel adoption, the old and the new system are run in parallel initially, so that all the users can get used to the new system, but still can do their work using the old system if they want to or need to do so. Phased adoption means that the adoption happens in several phases, so that after each phase the system is a little closer to being fully adopted by the organization.
The adoption strategy has to be selected before adoption begins, and is chosen based on the goals to be achieved and on the type of system to be implemented. The three types of adoption, Big Bang, parallel adoption and phased adoption, range from an instant switch to a strategy where users progressively start using the new system over a certain period of time (which can be weeks, months or even years).
The actual selection is done by prioritizing the goals to be achieved and then matching a strategy against it (Eason, 1988). Eason defines the following goals:
If a large critical mass is, or might be, needed for the system to work effectively (e.g. due to network effects ), a big bang strategy might be the answer. (Rogers, 1995)
Minimising risk to the ongoing operation of the organization can be very important. Parallel and phased introductions might help to control these risks, depending on the situation.
The organization has to be ready for the changeover. Socio-technical preparations such as training sessions and ready-made scenarios must be clear.
If the new system is designed to deal with new requirements, such as business process reengineering , the speed at which the organization is changing over to the new processes or attempting to meet other new requirements.
The system might need to be adjusted to the users needs. In this case, the chosen strategy must provide the opportunity to do so.
Table Eason Matrix
The actual selection of adoption strategy depends on far more factors then these goals, but they create a window to choose one of the types. Other criteria are called variables (Gallivan, 1996). Gallivan suggests that the appropriate adoption types depends on:
Innovativeness of the individuals Attributes of the ones that are to adopt the innovation/system
The type of innovation Is it a process or product innovation?
Attributes of the innovation itself Preparedness, communicability and divisibility
The implementation complexity. How complex is the implementation or what is it is extent?
These variables are of a higher level than the criteria of Eason and should be handled as such. Based on table 1 and on the mentioned higher level variables by Gallivan, one can make a selection of an appropriate strategy to choose.
Figure 1: Organization preparation Process
In order to prepare the organization for the adoption of the new system, the changes that will take place need to be determined. This is necessary to be able to have a plan or an overview of the changeover, and can be done by creating requirements for the system. Once the management has determined the requirements in a report of determined changes, they need to agree upon them to be able to move on with the change-process. If there is no agreement, the management needs to discuss the requirements again and again until they do agree. If agreement is achieved and the agreement contract is signed, the organization can take further steps. So now the test-phase can be prepared, in which the validity of the data that will be used will be checked and in which trials will be held (Eason, 1988).
In parallel, it is highly recommended that a comprehensive user adoption plan be prepared working together with the business and the affected users. This plan should consider all pre- and post- system rollout communications; user training & documentation; any internal marketing efforts that will be undertaken to drive adoption such as system branding or swag; as well as troubleshooting assistance during the rollout (i.e. extended help desk hours and/or a hotline, and identification of key contacts for each affected business area).
. | https://en.wikipedia.org/wiki/Software_adoption |
In a software development team, a software analyst [ 1 ] is the person who monitors the software development process , performs configuration management , identifies safety, performance, and compliance issues, and prepares software requirements and specification ( Software Requirements Specification ) documents. [ 2 ] [ 3 ] [ unreliable source? ] [ 4 ] The software analyst is the seam between the software users and the software developers. [ 2 ] [ unreliable source? ] They convey the demands of software users to the developers. [ 2 ] [ unreliable source? ] | https://en.wikipedia.org/wiki/Software_analyst |
In computer programming and software engineering , software brittleness is the increased difficulty in fixing older software that may appear reliable, but instead, fails, when presented with unusual data or data that is altered in a seemingly minor way. The phrase is derived from analogies to brittleness in metalworking . [ 1 ]
When software is new, it is very malleable; it can be formed to be whatever is wanted by the implementers. But as the software in a given project grows larger and larger, and develops a larger base of users with long experience with the software, it becomes less and less malleable. Like a metal that has been work-hardened, the software becomes a legacy system , brittle and unable to be easily maintained without fracturing the entire system. [ citation needed ]
Brittleness in software can be caused by algorithms that do not work well for the full range of input data. Following, are some examples:
Very often, an old codebase is simply abandoned in favor of a brand-new one (which is intended to be free of many of the burdens of the legacy system; a.k.a. a rewrite ) created from scratch, but this can be an expensive and time-consuming process.
Some examples and reasons behind software brittleness: | https://en.wikipedia.org/wiki/Software_brittleness |
A software calculator is a calculator that has been implemented as a computer program , rather than as a physical hardware device.
They are among the simpler interactive software tools, and, as such, they provide operations for the user to select one at a time. They can be used to perform any process that consists of a sequence of steps each of which applies one of these operations, and have no purpose other than these processes, because the operations are the sole, or at least the primary, features of the calculator, rather than being secondary features that support other functionality that is not normally known simply as calculation. [ 1 ]
As a calculator , rather than a computer , they usually have a small set of relatively simple operations, perform short processes that are not compute intensive and do not accept large amounts of input data or produce many results, though many software calculators can emulate handheld scientific calculator and graphing calculator features such as trigonometric functions , approximations of pi , and making plots of functions.
Software calculators are available for many different platforms , and they can be:
Modern computers first emerged in the 1940s and 1950s. The software that they ran was naturally used to perform calculations, but it was specially designed for a substantial application that was not limited to simple calculations. For example, the LEO computer was designed to run business application software such as payroll .
Software specifically to perform calculations as its main purpose was first written in the 1960s, and the first software package for general calculations to obtain widespread use was released in 1978. [ 2 ] This was VisiCalc and it was called an interactive visible calculator , but it was actually a spreadsheet , and these are now not normally known simply as calculators.
The Unix version released in 1979, V7 Unix, contained a command-line accessible calculator.
Calculators have been used since ancient times and until the advent of software they were physical, hardware machines. The most recent hardware calculators are electronic hand-held devices with buttons for digits and operations, and a small display for inputs and results.
The first software calculators imitated these hardware calculators by implementing the same functionality with mouse-operated, rather than finger-operated, buttons. Such software calculators first emerged in the 1980s as part of the original Macintosh operating system ( System 1 ) and the Windows operating system ( Windows 1.0 ).
Some software calculators directly simulate one of the hardware calculators, by presenting an image that looks like the calculator, and by providing the same functionality.
There is now a very wide range of software calculators, and searching the Internet produces very large numbers of programs that are called calculators .
The results include numerical calculators that apply arithmetic operations or mathematical functions to numbers, and that produce numerical results or graphs of numerical functions, plus some non-numerical tools and games that are also called calculators.
Many of the results are calculators that do not imitate or simulate hardware calculators, but that take advantage of the greater power of computer software to implement alternative types of calculators. Software calculators are provided on the Internet which are customizable to use any conceivable algebraic expression. These user-customizable software calculators can also be used in conjunction with formula or equation creation capabilities so that the software calculator can now be created to perform all possible mathematical functions. No longer limited to a set of trigonometric and simple algebraic expressions, versions of the software calculator are now tailored to any and all topical applications.
Every type of hardware calculator has been implemented in software, including conversion , financial , graphing , programmable and scientific calculators.
Other numerical calculators that do not imitate traditional hardware calculators include:
Not all software-based calculators take numerical data or algebraic expressions as their input. Calculators can also take in arbitrary information ranging from lifestyle information to scientific notation. Some examples of these types of software calculators include:
There are also types of software used to help solve games that are sometimes referred to as calculators, including:
There are many interactive software packages that provide user-accessible calculation features, but that are not normally called calculators , because the calculation features play only a supporting role rather than being an end in themselves. These include: | https://en.wikipedia.org/wiki/Software_calculator |
Software categories are groups of software . They allow software to be understood in terms of those categories, instead of the particularities of each package. Different classification schemes consider different aspects of software.
Computer software can be put into categories based on common function, type, or field of use. There are three broad classifications:
The GNU Project categorizes software by copyright status: free software , open source software , public domain software , copylefted software, noncopylefted free software, lax permissive licensed software, GPL -covered software, the GNU operating system , GNU programs, GNU software, FSF -copyrighted GNU software, nonfree software, proprietary software , freeware , shareware , private software and commercial software . [ 1 ]
Free software is software that comes with permission for anyone to use, copy and distribute , either verbatim or with modifications, either gratis or for a fee. In particular, this means that source code must be available. "If it's not the source, it's not software." If a program is free, then it can potentially be included in a free operating system such as GNU, or free versions of the Linux system.
Free software in the sense of copyright license (and the GNU project) is a matter
of freedom, not price. However proprietary software companies typically use the term "free software" to refer to price. Sometimes this means a binary copy can be obtained at no charge; sometimes this means a copy is bundled with a computer for sale at no additional charge. [ 1 ]
Open-source software is software with its source code made available under a certain license to its licensees. It can be used and disseminated at any point, the source code is open and can be modified as required. The one condition with this type of software is that when changes are made users should make these changes known to others. One of the key characteristics of open source software is that it is the shared intellectual property of all developers and users. The Linux operating system is one of the best-known examples of a collection of open-source software. [ 2 ]
Copylefted software is free software whose distribution terms ensure that all copies of all versions carry more or less the same distribution terms. This means, for instance, that copyleft licenses generally disallow others to add additional requirements to the software (though a limited set of safe added requirements can be allowed) and require making source code available. This shields the program, and its modified versions, from some of the common ways of making a program proprietary. Some copyleft licenses block other means of turning software proprietary.
Copyleft is a general concept. Copylefting an actual program requires a specific set of distribution terms. Different copyleft licenses are usually "incompatible" due to varying terms, which makes it illegal to merge the code using one license with the code using the other license. If two pieces of software use the same license, they are generally mergeable. [ 1 ]
Noncopylefted free software comes from the author with permission to redistribute modify and add license restrictions.
If a program is free but not copylefted, then some copies or modified versions may not be free. A software company can compile the program, with or without modifications, and distribute the executable file as a proprietary software product. The X Window System illustrates this approach. The X Consortium releases X11 with distribution terms that make it non-copylefted free software. If you wish, you can get a copy that has those distribution terms and is free, however nonfree versions are available. There are workstations and PC graphics boards for which nonfree versions are the only versions that will work. The developers of X11 made X11 nonfree for a while; they were able to do this because others had contributed their code under the same non-copyleft license. [ 1 ]
Shareware is software that comes with permission to redistribute copies but says that anyone who continues to use a copy is required to pay. Shareware is not free software or even semi-free. For most shareware, source code is not available; thus, the program cannot be modified. Shareware does not come with permission to make a copy and install it without paying a license fee, including for nonprofit activity. [ 1 ]
Like shareware, freeware is software available for download and distribution without any initial payment. Freeware never has an associated fee. Things like minor program updates and small games are commonly distributed as freeware. Though freeware is cost-free, it is copyrighted , so other people can not market the software as their own. [ 3 ]
This classification has seven major elements. They are: platform and management , education and reference , home and entertainment, content and communication , operations and professional, product manufacturing and service delivery, and line of business . | https://en.wikipedia.org/wiki/Software_categories |
A software component is a modular unit of software that encapsulates specific functionality. [ 1 ] The desired characteristics of a component are reusability and maintainability . [ 1 ]
Components allow software development to assemble software with reliable parts rather than writing code for every aspect; allowing for implementation to be more like factory assembly than custom building.
Desirable attributes of a component include but are not limited to:
Some components are built in-house by the same organization or team building the software system . Some are third-party , developed elsewhere and assembled into the software system. [ 2 ]
For large-scale systems, component-based development encourages a disciplined process to manage complexity . [ 3 ]
Some components conform to a framework technology that allows them to be consumed in a well-known way. Examples include: CORBA , COM , Enterprise JavaBeans , and the .NET Framework . [ 4 ] [ 5 ]
Component design is often modeled visually. In Unified Modeling Language (UML) 2.0 a component is shown as a rectangle, and an interface is shown as a lollipop to indicate a provided interface and as a socket to indicate consumption of an interface.
The idea of reusable software components was promoted by Douglas McIlroy in his presentation at the NATO Software Engineering Conference of 1968. [ 6 ] (One goal of that conference was to resolve the so-called software crisis of the time.) In the 1970s, McIlroy put this idea into practice with the addition of the pipeline feature to the Unix operating system .
Brad Cox refined the concept of a software component in the 1980s. [ 7 ] He attempted to create an infrastructure and market for reusable third-party components by inventing the Objective-C programming language. [ 8 ]
IBM introduced System Object Model (SOM) in the early 1990s. [ 9 ]
Microsoft introduced Component Object Model (COM)
in the early 1990s. Microsoft built many domain-specific component technologies on COM, including Distributed Component Object Model (DCOM), Object Linking and Embedding (OLE), and ActiveX. | https://en.wikipedia.org/wiki/Software_component |
Software configuration management ( SCM ), a.k.a. software change and configuration management ( SCCM ), [ 1 ] is the software engineering practice of tracking and controlling changes to a software system ; part of the larger cross-disciplinary field of configuration management (CM). [ 2 ] SCM includes version control and the establishment of baselines .
The goals of SCM include: [ citation needed ]
With the introduction of cloud computing and DevOps the purposes of SCM tools have become merged in some cases. The SCM tools themselves have become virtual appliances that can be instantiated as virtual machines and saved with state and version. The tools can model and manage cloud-based virtual resources, including virtual appliances, storage units, and software bundles. The roles and responsibilities of the actors have become merged as well with developers now being able to dynamically instantiate virtual servers and related resources. [ 3 ] | https://en.wikipedia.org/wiki/Software_configuration_management |
Software construction is a software engineering discipline. It is the detailed creation of working meaningful software through a combination of coding , verification , unit testing , integration testing , and debugging . It is linked to all the other software engineering disciplines, most strongly to software design and software testing . [ 1 ]
The need to reduce complexity is mainly driven by limited ability of most people to hold complex structures and information in their working memories. Reduced complexity is achieved through emphasizing the creation of code that is simple and readable rather than clever. Minimizing complexity is accomplished through making use of standards , and through numerous specific techniques in coding . It is also supported by the construction-focused quality techniques. [ 2 ]
Anticipating change helps software engineers build extensible software, which means they can enhance a software product without disrupting the underlying structure. [ 2 ] Research over 25 years showed that the cost of rework can be 10 to 100 times (5 to 10 times for smaller projects) more expensive than getting the requirements right the first time. Given that 25% of the requirements change during development on average project, the need to reduce the cost of rework elucidates the need for anticipating change. [ 3 ]
Constructing for verification means building software in such a way that faults can be ferreted out readily by the software engineers writing the software , as well as during independent testing and operational activities. Specific techniques that support constructing for verification include following coding standards to support code reviews , unit testing , organizing code to support automated testing , and restricted use of complex or hard-to- understand language structures, among others. [ 2 ]
Systematic reuse can enable significant software productivity, quality, and cost improvements. Reuse has two closely related facets: [ 2 ]
Standards, whether external (created by international organizations) or internal (created at the corporate level), that directly affect construction issues include: [ 2 ]
Numerous models have been created to develop software , some of which emphasize construction more than others. Some models are more linear from the construction point of view, such as the Waterfall and staged-delivery life cycle models. These models treat construction as an activity which occurs only after significant prerequisite work has been completed—including detailed requirements work, extensive design work, and detailed planning . Other models are more iterative , such as evolutionary prototyping , Extreme Programming , and Scrum . These approaches tend to treat construction as an activity that occurs concurrently with other software development activities, including requirements , design , and planning , or overlaps them. [ 1 ]
The choice of construction method is a key aspect of the construction planning activity. The choice of construction method affects the extent to which construction prerequisites (e.g. Requirements analysis , Software design , .. etc.) are performed, the order in which they are performed, and the degree to which they are expected to be completed before construction work begins. Construction planning also defines the order in which components are created and integrated, the software quality management processes, the allocation of task assignments to specific software engineers , and the other tasks, according to the chosen method . [ 1 ]
Numerous construction activities and artifacts can be measured, including code developed, code modified, code reused, code destroyed, code complexity, code inspection statistics, fault-fix and fault-find rates, effort, and scheduling. These measurements can be useful for purposes of managing construction, ensuring quality during construction, improving the construction process, as well as for other reasons. [ 1 ]
Software construction is driven by many practical considerations:
In order to account for the unanticipated gaps in the software design , during software construction some design modifications must be made on a smaller or larger scale to flesh out details of the software design . [ 4 ]
Low Fan-out is one of the design characteristics found to be beneficial by researchers. Information hiding proved to be a useful design technique in large programs that made them easier to modify by a factor of 4. [ 5 ]
Construction languages include all forms of communication by which a human can specify an executable problem solution to a computer. They include configuration languages, toolkit languages, and programming languages : [ 6 ]
Programmers working in a language they have used for three years or more are about 30 percent more productive than programmers with equivalent experience who are new to a language. High-level languages such as C++, Java, Smalltalk, and Visual Basic yield 5 to 15 times better productivity, reliability, simplicity, and comprehensibility than low-level languages such as assembly and C. Equivalent code has been shown to need fewer lines to be implemented in high level languages than in lower level languages. [ 7 ]
The following considerations apply to the software construction coding activity: [ 8 ]
The purpose of construction testing is to reduce the gap between the time at which faults are inserted into the code and the time those faults are detected. In some cases, construction testing is performed after code has been written. In test-first programming , test cases are created before code is written. Construction involves two forms of testing, which are often performed by the software engineer who wrote the code : [ 1 ]
Implementing software reuse entails more than creating and using libraries of assets. It requires formalizing the practice of reuse by integrating reuse processes and activities into the software life cycle . The tasks related to reuse in software construction during coding and testing are: [ 1 ]
The primary techniques used to ensure the quality of code as it is constructed include: [ 15 ]
Studies have shown that a combination of these techniques needs to be used to achieve a high defect detection rate. Other studies showed that different people tend to find different defects. One study found that the extreme programming practices of pair programming , desk checking , unit testing , integration testing , and regression testing can achieve a 90% defect detection rate. [ 16 ] An experiment involving experienced programmers found that on average they were able to find 5 errors (9 at best) out of 15 errors by testing. [ 18 ]
80% of the errors tend to be concentrated in 20% of the project's classes and routines. 50% of the errors are found in 5% of the project's classes. IBM was able to reduce the customer reported defects by a factor of ten to one and to reduce their maintenance budget by 45% in its IMS system by repairing or rewriting only 31 out of 425 classes. Around 20% of a project's routines contribute to 80% of the development costs. A classic study by IBM found that few error-prone routines of OS/360 were the most expensive entities. They had around 50 defects per 1000 lines of code and fixing them costs 10 times what it took to develop the whole system. [ 18 ]
A key activity during construction is the integration of separately constructed routines , classes , components , and subsystems. In addition, a particular software system may need to be integrated with other software or hardware systems. Concerns related to construction integration include planning the sequence in which components will be integrated, creating scaffolding to support interim versions of the software , determining the degree of testing and quality work performed on components before they are integrated, and determining points in the project at which interim versions of the software are tested. [ 1 ]
Object-oriented languages support a series of runtime mechanisms that increase the flexibility and adaptability of the programs like data abstraction , encapsulation , modularity , inheritance , polymorphism , and reflection . [ 19 ] [ 20 ]
Data abstraction is the process by which data and programs are defined with a representation similar in form to its meaning, while hiding away the implementation details. [ 21 ] Academic research showed that data abstraction makes programs about 30% easier to understand than functional programs. [ 10 ]
Assertions are executable predicates which are placed in a program that allow runtime checks of the program. [ 19 ] Design by contract is a development approach in which preconditions and postconditions are included for each routine. Defensive programming is the protection a routine from being broken by invalid inputs. [ 22 ]
Error-handling refers to the programming practice of anticipating and coding for error conditions that may arise when the program runs. Exception-handling is a programming-language construct or hardware mechanism designed to handle the occurrence of exceptions, special conditions that change the normal flow of program execution. [ 23 ] Fault tolerance is a collection of techniques that increase software reliability by detecting errors and then recovering from them if possible or containing their effects if recovery is not possible. [ 22 ]
State-based programming is a programming technology using finite state machines to describe program behaviors. [ 22 ] A table-driven method is a schema that uses tables to look up information rather than using logic statements (such as if and case). [ 24 ]
Runtime configuration is a technique that binds variable values and program settings when the program is running, usually by updating and reading configuration files in a just-in-time mode. Internationalization is the technical activity of preparing a program, usually interactive software, to support multiple locales. The corresponding activity, localization , is the activity of modifying a program to support a specific local language. [ 24 ] | https://en.wikipedia.org/wiki/Software_construction |
Software crisis is a term used in the early days of computing science for the difficulty of writing useful and efficient computer programs in the required time. The software crisis was due to the rapid increases in computer power and the complexity of the problems that could be tackled. With the increase in the complexity of the software, many software problems arose because existing methods were inadequate.
The term "software crisis" was coined by some attendees at the first NATO Software Engineering Conference in 1968 at Garmisch , Germany. [ 1 ] [ 2 ] Edsger Dijkstra 's 1972 Turing Award Lecture makes reference to this same problem: [ 3 ]
The major cause of the software crisis is that the machines have become several orders of magnitude more powerful! To put it quite bluntly: as long as there were no machines, programming was no problem at all; when we had a few weak computers, programming became a mild problem, and now we have gigantic computers, programming has become an equally gigantic problem.
The causes of the software crisis were linked to the overall complexity of hardware and the software development process. The crisis manifested itself in several ways:
The main cause is that improvements in computing power had outpaced the ability of programmers to effectively use those capabilities. Various processes and methodologies have been developed over the last few decades to improve software quality management such as procedural programming and object-oriented programming . However, software projects that are large, complicated, poorly specified, or involve unfamiliar aspects, are still vulnerable to large, unanticipated problems. | https://en.wikipedia.org/wiki/Software_crisis |
Software design is the process of conceptualizing how a software system will work before it is implemented or modified. [ 1 ] Software design also refers to the direct result of the design process – the concepts of how the software will work which consists of both design documentation and undocumented concepts.
Software design usually is directed by goals for the resulting system and involves problem-solving and planning – including both
high-level software architecture and low-level component and algorithm design .
In terms of the waterfall development process , software design is the activity of following requirements specification and before coding . [ 2 ]
The design process enables a designer to model various aspects of a software system before it exists.
Creativity, past experience, a sense of what makes "good" software, and a commitment to quality are success factors for a competent design. However, the design process is not always a straightforward procedure.
The software design model can be compared to an architected plan for a house. High-level plans represent the totality of the house (e.g., a three-dimensional rendering of the house). Lower-level plans provide guidance for constructing each detail (e.g., the plumbing lay). Similarly, the software design model provides a variety of views of the proposed software solution.
Software systems inherently deal with uncertainties, and the size of software components can significantly influence a system's outcomes, both positively and negatively. Neal Ford and Mark Richards propose an iterative approach to address the challenge of identifying and right-sizing components. This method emphasizes continuous refinement as teams develop a more nuanced understanding of system behavior and requirements. [ 3 ]
The approach typically involves a cycle with several stages: [ 3 ]
This cycle serves as a general framework and can be adapted to different domains.
Software design documentation may be reviewed or presented to allow constraints, specifications and even requirements to be adjusted prior to coding . Redesign may occur after a review of a programmed simulation or prototype . It is possible to design software in the process of coding, without a plan or requirement analysis, [ 4 ] but for more complex projects this is less feasible. A separate design prior to coding allows for multidisciplinary designers and subject-matter experts (SMEs) to collaborate with programmers in order to produce software that is useful and technically sound.
One component of software design is software requirements analysis (SRA). SRA is a part of the software development process that lists specifications used in software engineering .
The output of the analysis is smaller problems to solve.
In contrast, the design focuses on capabilities, and thus multiple designs for the same problem can exist. Depending on the environment, the design often varies, whether it is created from reliable frameworks or implemented with suitable design patterns .
A design process may include the production of artifacts such as flow chart , use case , Pseudocode , Unified Modeling Language model and other Fundamental modeling concepts . For user centered software, design may involve user experience design yielding a storyboard to help determine those specifications.
Sometimes the output of a design process is
design documentation .
Basic design principles enable a software engineer to navigate the design process. Davis [ 5 ] suggests a set of principles for software design, which have been adapted and extended in the following list:
Design concepts provide a designer with a foundation from which more sophisticated methods can be applied. A set of design concepts has evolved including:
In his object model, Grady Booch mentions Abstraction , Encapsulation , Modularisation , and Hierarchy as fundamental software design principles. [ 6 ] The acronym PHAME (Principles of Hierarchy, Abstraction, Modularisation, and Encapsulation) is sometimes used to refer to these four fundamental principles. [ 7 ]
There are many aspects to consider in the design of a piece of software. The importance of each consideration should reflect the goals and expectations that the software is being created to meet. Some of these aspects are:
A modeling language can be used to express information, knowledge or systems in a structure that is defined by a consistent set of rules. These rules are used for interpretation of the components within the structure. A modeling language can be graphical or textual. Examples of graphical modeling languages for software design include:
A software designer may identify a design aspect which has been visited and perhaps even solved by others in the past. A template or pattern describing a solution to a common problem is known as a design pattern . The reuse of such patterns can increase software development velocity. [ 11 ]
The difficulty of using the term "design" in relation to software is that in some senses, the source code of a program is the design for the program that it produces. To the extent that this is true, "software design" refers to the design of the design. Edsger W. Dijkstra referred to this layering of semantic levels as the "radical novelty" of computer programming, [ 12 ] and Donald Knuth used his experience writing TeX to describe the futility of attempting to design a program prior to implementing it:
T E X would have been a complete failure if I had merely specified it and not participated fully in its initial implementation. The process of implementation constantly led me to unanticipated questions and to new insights about how the original specifications could be improved. [ 13 ]
^ Roger S. Pressman (2001). Software engineering: a practitioner's approach . McGraw-Hill. ISBN 0-07-365578-3 . | https://en.wikipedia.org/wiki/Software_design |
Software development is the process of designing and implementing a software solution to satisfy a user . The process is more encompassing than programming , writing code , in that it includes conceiving the goal, evaluating feasibility, analyzing requirements , design , testing and release . The process is part of software engineering which also includes organizational management , project management , configuration management and other aspects. [ 1 ]
Software development involves many skills and job specializations including programming , testing , documentation , graphic design , user support , marketing , and fundraising .
Software development involves many tools including: compiler , integrated development environment (IDE), version control , computer-aided software engineering , and word processor .
The details of the process used for a development effort varies. The process may be confined to a formal, documented standard , or it can be customized and emergent for the development effort. The process may be sequential, in which each major phase (i.e. design, implement and test) is completed before the next begins, but an iterative approach – where small aspects are separately designed, implemented and tested – can reduce risk and cost and increase quality.
Each of the available methodologies are best suited to specific kinds of projects, based on various technical, organizational, project, and team considerations. [ 3 ]
Another focus in many programming methodologies is the idea of trying to catch issues such as security vulnerabilities and bugs as early as possible ( shift-left testing ) to reduce the cost of tracking and fixing them. [ 13 ]
In 2009, it was estimated that 32 percent of software projects were delivered on time and budget, and with the full functionality. An additional 44 percent were delivered, but missing at least one of these features. The remaining 24 percent were cancelled prior to release. [ 14 ]
Software development life cycle refers to the systematic process of developing applications . [ 15 ]
The sources of ideas for software products are plentiful. These ideas can come from market research including the demographics of potential new customers, existing customers, sales prospects who rejected the product, other internal software development staff, or a creative third party. Ideas for software products are usually first evaluated by marketing personnel for economic feasibility, fit with existing channels of distribution, possible effects on existing product lines, required features , and fit with the company's marketing objectives. In the marketing evaluation phase, the cost and time assumptions become evaluated. [ 16 ] The feasibility analysis estimates the project's return on investment , its development cost and timeframe. Based on this analysis, the company can make a business decision to invest in further development. [ 17 ] After deciding to develop the software, the company is focused on delivering the product at or below the estimated cost and time, and with a high standard of quality (i.e., lack of bugs) and the desired functionality. Nevertheless, most software projects run late and sometimes compromises are made in features or quality to meet a deadline. [ 18 ]
Software analysis begins with a requirements analysis to capture the business needs of the software. [ 19 ] Challenges for the identification of needs are that current or potential users may have different and incompatible needs, may not understand their own needs, and change their needs during the process of software development. [ 20 ] Ultimately, the result of analysis is a detailed specification for the product that developers can work from. Software analysts often decompose the project into smaller objects, components that can be reused for increased cost-effectiveness, efficiency, and reliability. [ 19 ] Decomposing the project may enable a multi-threaded implementation that runs significantly faster on multiprocessor computers. [ 21 ]
During the analysis and design phases of software development, structured analysis is often used to break down the customer's requirements into pieces that can be implemented by software programmers. [ 22 ] The underlying logic of the program may be represented in data-flow diagrams , data dictionaries , pseudocode , state transition diagrams , and/or entity relationship diagrams . [ 23 ] If the project incorporates a piece of legacy software that has not been modeled, this software may be modeled to help ensure it is correctly incorporated with the newer software. [ 24 ]
Design involves choices about the implementation of the software, such as which programming languages and database software to use, or how the hardware and network communications will be organized. Design may be iterative with users consulted about their needs in a process of trial and error . Design often involves people expert in aspect such as database design , screen architecture, and the performance of servers and other hardware. [ 19 ] Designers often attempt to find patterns in the software's functionality to spin off distinct modules that can be reused with object-oriented programming . An example of this is the model–view–controller , an interface between a graphical user interface and the backend . [ 25 ]
The central feature of software development is creating and understanding the software that implements the desired functionality. [ 26 ] There are various strategies for writing the code. Cohesive software has various components that are independent from each other. [ 19 ] Coupling is the interrelation of different software components, which is viewed as undesirable because it increases the difficulty of maintenance . [ 27 ] Often, software programmers do not follow industry best practices, resulting in code that is inefficient, difficult to understand, or lacking documentation on its functionality. [ 28 ] These standards are especially likely to break down in the presence of deadlines. [ 29 ] As a result, testing, debugging, and revising the code becomes much more difficult. Code refactoring , for example adding more comments to the code, is a solution to improve the understandability of code. [ 30 ]
Testing is the process of ensuring that the code executes correctly and without errors. Debugging is performed by each software developer on their own code to confirm that the code does what it is intended to. In particular, it is crucial that the software executes on all inputs, even if the result is incorrect. [ 31 ] Code reviews by other developers are often used to scrutinize new code added to the project, and according to some estimates dramatically reduce the number of bugs persisting after testing is complete. [ 32 ] Once the code has been submitted, quality assurance —a separate department of non-programmers for most large companies—test the accuracy of the entire software product. Acceptance tests derived from the original software requirements are a popular tool for this. [ 31 ] Quality testing also often includes stress and load checking (whether the software is robust to heavy levels of input or usage), integration testing (to ensure that the software is adequately integrated with other software), and compatibility testing (measuring the software's performance across different operating systems or browsers). [ 31 ] When tests are written before the code, this is called test-driven development . [ 33 ]
Production is the phase in which software is deployed to the end user. [ 34 ] During production, the developer may create technical support resources for users [ 35 ] [ 34 ] or a process for fixing bugs and errors that were not caught earlier. There might also be a return to earlier development phases if user needs changed or were misunderstood. [ 34 ]
Software development is performed by software developers , usually working on a team. Efficient communications between team members is essential to success. This is more easily achieved if the team is small, used to working together, and located near each other. [ 36 ] Communications also help identify problems at an earlier state of development and avoid duplicated effort. Many development projects avoid the risk of losing essential knowledge held by only one employee by ensuring that multiple workers are familiar with each component. [ 37 ] Software development involves professionals from various fields, not just software programmers but also product managers who set the strategy and roadmap for the product, [ 38 ] individuals specialized in testing, documentation writing, graphic design , user support, marketing , and fundraising. Although workers for proprietary software are paid, most contributors to open-source software are volunteers. [ 39 ] Alternately, they may be paid by companies whose business model does not involve selling the software, but something else—such as services and modifications to open source software. [ 40 ]
Computer-aided software engineering (CASE) is tools for the partial automation of software development. [ 41 ] CASE enables designers to sketch out the logic of a program, whether one to be written, or an already existing one to help integrate it with new code or reverse engineer it (for example, to change the programming language ). [ 42 ]
Documentation comes in two forms that are usually kept separate—that intended for software developers, and that made available to the end user to help them use the software. [ 43 ] [ 44 ] Most developer documentation is in the form of code comments for each file, class , and method that cover the application programming interface (API)—how the piece of software can be accessed by another—and often implementation details. [ 45 ] This documentation is helpful for new developers to understand the project when they begin working on it. [ 46 ] In agile development, the documentation is often written at the same time as the code. [ 47 ] User documentation is more frequently written by technical writers . [ 48 ]
Accurate estimation is crucial at the feasibility stage and in delivering the product on time and within budget. The process of generating estimations is often delegated by the project manager . [ 49 ] Because the effort estimation is directly related to the size of the complete application, it is strongly influenced by addition of features in the requirements—the more requirements, the higher the development cost. Aspects not related to functionality, such as the experience of the software developers and code reusability, are also essential to consider in estimation. [ 50 ] As of 2019 [update] , most of the tools for estimating the amount of time and resources for software development were designed for conventional applications and are not applicable to web applications or mobile applications . [ 51 ]
An integrated development environment (IDE) supports software development with enhanced features compared to a simple text editor . [ 52 ] IDEs often include automated compiling , syntax highlighting of errors, [ 53 ] debugging assistance, [ 54 ] integration with version control , and semi-automation of tests. [ 52 ]
Version control is a popular way of managing changes made to the software. Whenever a new version is checked in, the software saves a backup of all modified files. If multiple programmers are working on the software simultaneously, it manages the merging of their code changes. The software highlights cases where there is a conflict between two sets of changes and allows programmers to fix the conflict. [ 55 ]
A view model is a framework that provides the viewpoints on the system and its environment , to be used in the software development process . It is a graphical representation of the underlying semantics of a view.
The purpose of viewpoints and views is to enable human engineers to comprehend very complex systems and to organize the elements of the problem around domains of expertise . In the engineering of physically intensive systems, viewpoints often correspond to capabilities and responsibilities within the engineering organization. [ 56 ]
Fitness functions are automated and objective tests to ensure that the new developments don't deviate from the established constraints, checks and compliance controls. [ 57 ]
Intellectual property can be an issue when developers integrate open-source code or libraries into a proprietary product, because most open-source licenses used for software require that modifications be released under the same license. As an alternative, developers may choose a proprietary alternative or write their own software module. [ 58 ] | https://en.wikipedia.org/wiki/Software_developer |
Software diagnosis (also: software diagnostics ) refers to concepts, techniques, and tools that allow for obtaining findings, conclusions, and evaluations about software systems and their implementation, composition, behaviour, and evolution. It serves as means to monitor, steer, observe and optimize software development, software maintenance, and software re-engineering in the sense of a business intelligence approach specific to software systems. It is generally based on the automatic extraction, analysis, and visualization of corresponding information sources of the software system. It can also be manually done and not automatic.
Software diagnosis supports all branches of software engineering , in particular project management, quality management, risk management as well as implementation and test. Its main strength is to support all stakeholders of software projects (in particular during software maintenance and for software re-engineering tasks [ 1 ] ) and to provide effective communication means for software development projects. For example, software diagnosis facilitates "bridging an essential information gap between management and development, improve awareness, and serve as early risk detection instrument". [ 2 ] Software diagnosis includes assessment methods for "perfective maintenance" that, for example, apply "visual analysis techniques to combine multiple indicators for low maintainability, including code complexity and entanglement with other parts of the system, and recent changes applied to the code". [ 3 ]
In contrast to manifold approaches and techniques in software engineering , software diagnosis does not depend on programming languages, modeling techniques, software development processes or the specific techniques used in the various stages of the software development process. Instead, software diagnosis aims at analyzing and evaluating the software system in its as-is state and based on system-generated information to bypass any subjective or potentially outdated information sources (e.g., initial software models). For it, software diagnosis combines and relates sources of information that are typically not directly linked. Examples:
The core principle of software diagnosis is to automatically extract information from all available information sources of a given software projects such as source code base, project repository, code metrics, execution traces, [ 6 ] test results, etc. To combine information, software-specific data mining, analysis, and visualization techniques are applied. Its strength results, among various reasons, from integrating decoupled information spaces in the scope of a typical software project, for example development and developer activities (recorded by the repository) and code and quality metrics (derived by analyzing source code) or key performance indicators (KPIs).
Examples of software diagnosis tools include software maps and software metrics .
Software diagnosis—in contrast to many approaches in software engineering—does not assume that developer capabilities, development methods, programming or modeling languages are right or wrong (or better or worse compared to each other): Software diagnosis aims at giving insight into a given software system and its status regardless of the methods, languages, or models used to create and maintain the system. | https://en.wikipedia.org/wiki/Software_diagnosis |
Software distribution is the process of delivering software to the end user. [ 1 ]
GNU Autotools are widely used for which consist of source files written in C++ and the C programming language , but are not limited to these.
Distribution of software to small mobile devices such as phones, PDAs and other hand-held terminals is a particular challenge due to their inconsistent connection to the Internet. Some tools that cater to this category of devices are:
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Software_distribution |
Software diversity is a research field about the comprehension and engineering of diversity in the context of software.
The different areas of software diversity are discussed in surveys on diversity for fault-tolerance [ 1 ] or for security. [ 2 ] [ 3 ]
The main areas are:
It is possible to amplify software diversity through automated transformation processes that create synthetic diversity. A "multicompiler" is compiler embedding a diversification engine. [ 5 ] A multi-variant execution environment (MVEE) is responsible for selecting the variant to execute and compare the output. [ 6 ]
Fred Cohen was among the very early promoters of such an approach. He proposed a series of rewriting and code reordering transformations that aim at producing massive quantities of different versions of operating systems functions. [ 7 ] These ideas have been developed over the years and have led to the construction of integrated obfuscation schemes to protect key functions in large software systems. [ 8 ]
Another approach to increase software diversity of protection consists in adding randomness in certain core processes, such as memory loading. Randomness implies that all versions of the same program run differently from each other, which in turn creates a diversity of program behaviors. This idea was initially proposed and experimented by Stephanie Forrest and her colleagues. [ 9 ]
Recent work on automatic software diversity explores different forms of program transformations that slightly vary the behavior of programs. The goal is to evolve one program into a population of diverse programs that all provide similar services to users, but with a different code. [ 10 ] This diversity of code enhances the protection of users against one single attack that could crash all programs at the same time.
Transformation operators include: [ 11 ]
It is known that some functionalities are available in multiple interchangeable implementations. This natural diversity can be exploited, for example it has been shown valuable to increase security in cloud systems . [ 12 ] | https://en.wikipedia.org/wiki/Software_diversity |
In software engineering , software durability means the solution ability of serviceability of software and to meet user's needs for a relatively long time. Software durability is important for user's satisfaction. For a software security to be durable, it must allow an organization to adjust the software to business needs that are constantly evolving, often in impulsive ways. [ 1 ]
Durability of software depends on four characteristics mainly; i.e. software trustworthiness, Human Trust for Serviceability , software dependability and software usability . [ citation needed ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Software_durability |
Software Ecosystem is a book written by David G. Messerschmitt and Clemens Szyperski that explains the essence and effects of a " software ecosystem ", defined as a set of businesses functioning as a unit and interacting with a shared market for software and services , together with relationships among them. These relationships are frequently underpinned by a common technological platform and operate through the exchange of information, resources, and artifacts. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ]
In the context of software analysis , the term software ecosystem is defined by Lungu [ 6 ] as “a collection of software projects, which are developed and co-evolve in the same environment”. The environment can be organizational (a company), social (an open-source community), or technical (the Ruby ecosystem). The ecosystem metaphor is used in order to denote an analysis which takes into account multiple software systems. [ 7 ] The most frequent of such analyses is static analysis of the source code of the component systems of the ecosystem.
Software analysis is the process of systematically examining and evaluating software applications to assess their design, functionality, performance, and adherence to requirements. This involves reviewing code, testing the software for bugs or vulnerabilities, ensuring compliance with design specifications, and optimizing for efficiency. Software analysis helps identify potential issues early in the development cycle, improves overall quality, and ensures that the software meets the intended goals. It includes techniques like static code analysis, dynamic analysis, and performance profiling to provide insights for better software maintenance and improvement. [ 8 ]
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Software_ecosystem |
A software engine is a core component of a complex software system . The word "engine" is a metaphor of a car 's engine . Thus a software engine is a complex subsystem .
There is no formal guideline for what should be called an engine, but the term has become widespread in the software industry . [ 1 ] [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/Software_engine |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.