title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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Synthesis and ion-exchange properties of thermally stable stannic selenite. | Stannic selenites have been synthesized under a variety of conditions. The most stable sample is prepared by mixing 0-0.5M solutions of stannic chloride and sodium selenite in the ratio of 1:1 at pH 1. It is a bifunctional amorphous material. A tentative structure has been proposed on the basis of chemical composition,... | 18,961,152 |
Determination of subnanogram amounts of chromium in different matrices by flameless atomic-absorption spectroscopy. | A carbon rod flameless atomizer is used for the determination of Cr in water, sea-water, sugar, glycine and blood. The reported analytical curves show that the quantitative determination of Cr in these matrices is feasible in the ppM-ppm range. The influence of the most common anionic and cationic interferents is repor... | 18,961,155 |
Behaviour of ferroin indicator in iron(ii)- dichromate titrations A Critical study. | A critical evaluation has been made of the optimum conditions for a successful direct and reverse titration of iron(II) with dichromate, with ferroin as indicator, taking into account the influence of acidity, the catalytic effect of iron(III) and the induction effect of the iron(II)-dichromate reaction on the indicato... | 18,961,159 |
Formation of hydrogen peroxide upon oxidation of oxalic acid in presence and absence of oxygen-II Oxygen as oxidant. | Hydrogen peroxide, m a mixture that is 0.1M in manganese(II) sulphate and sulphuric add and exposed to light from a tungsten lamp, decomposes slowly at room temperature in a nitrogen atmosphere. At 75 degrees the reaction is fairly rapid in the dark (about 20-25% in 4 hr) and about 60% faster in light. Presence of oxal... | 18,961,168 |
Spectrophotometric determination of dimethyl sulphoxide. | A spectrophotometric method for the determination of milligram quantities of dimethyl sulphoxide in aqueous solutions has been developed. The method is based on the medium effect on the visible absorption spectra of metal salt solutions. Out of several compounds investigated, iron(III) alum was chosen as most suitable ... | 18,961,176 |
Radiochemical separation of zirconium and hafnium from other radionuclides. | Radiozirconium and radiohafnium may be separated from all other radionuclides except scandium and protactinium by precipitation with mandelic acid from 5-10 M hydrochloric acid, using commercial zirconyl chloride as carrier. Scandium and protactinium are removed by dissolving the precipitate in sodium carbonate, then a... | 18,961,201 |
New tests for the detection of azide. | Two new, simple, reliable, and specific colour tests are described for the detection of azide. In one, the azide is heated with allyl isothiocyanate and water to form 1-allyl-2-tetrazoline-5-thione in solution; the latter gives a yellow precipitate on treatment with bismuth nitrate solution. Pyridine enhances the inten... | 18,961,203 |
Quantitative reflectometry-I Principles and scope. | The technique of quantitative reflectometry is critically investigated, the model being the quantitative determination of nickel in aqueous media. Direct reflectance measurements can be made on commercially available nickel test-strips which develop a pink or red colour in the presence of nickel ions. Relative precisio... | 18,961,217 |
Potentiometric determination of stepwise stability constants of vanadium, molybdenum and tungsten chelates formed with asparagine and glutamine. | The metal chelates of V(IV), Mo(VI) and W(VI) formed with asparagine and glutamine have been studied potentiometrically. Stepwise stability constants in O.1M sodium perchlorate at 25 degrees C are reported as follows. Asparagine chelates--log K(1)K(2) 14.50 and log K(3) 4.04 for V, log K(1) 8.06, log K(2) 7.29 and log ... | 18,961,248 |
Spectrophotometric determination of strychnine and methylatropine by extraction with tetrabromophenolphthalein ethyl ester. | A new application of monoacidic dyes is reported for the determination of strychnine and methylatropine. The method is based on solvent extraction into 1,2-dichloroethane of the ion-pair or addition compound formed between tetrabromophenolphthalein ethyl ester and quaternary ammonium salts or alkaloids. The absorbance ... | 18,961,259 |
Study of Cu(II)-hydrazine-6-methylpicolinaldehyde system: A new "in situ" reaction. | The Cu(II)-hydrazine-6-methylpicolinaldehyde system in solution is studied. The "in situ" reactions, based on the formation of a ligand by condensation of an amine and an aldehyde in the presence of the metal ion, and the consequent formation of the coloured Cu(I)-azine and Cu(l)-hydrazone complexes are reported. A new... | 18,961,260 |
A phosphorimetric investigation of the external heavy-atom effect in aqueous solution and its correlation with phosphorescence intensity and quantum yield. | Excitation and emission phosphorescence spectra, lifetimes, and relative quantum yields of benzene and ten monosubstituted benzenes were determined at 77 K in methanol/water 10/90 v/v and in sodium iodide/methanol/water solutions. Substituents CHO, COCH(3), COC(2)H(5), OH, OCH(3), H(3), C(2)H(5), CH(2)OH and N(CH(3))(2... | 18,961,273 |
Indirect polarographic determination of tripolyphosphate ions in the presence of other polyphosphates, with octyltin chloride. | Tripolyphosphate ions form a soluble complex with mono-octyltin cations, thus reducing the polarographic wave height ofthe octyltin. This provides a method for the determination of 2 x 10(-4)-4 x 10(-3)M tripolyphosphate in the presence of 2 x 10(-3)M ortho-, pyro-, trimeta-, and 10(-3)M tetrametaphosphate, together, o... | 18,961,280 |
Application of indirect methods in analysis by atomic-absorption spectrometry. | The use of indirect methods for the determination by atomic-absorption spectrometry of those elements not normally amenable to sensitive determination by this technique is reviewed. The available indirect methods are classified into five general types of procedure; specific reported procedures for the determination of ... | 18,961,303 |
Ultramicro atomic-absorption spectroscopy with a tungsten-filament atom-reservoir. | The detection and measurement of traces of zinc, lead, copper and silver by atomic-absorption spectroscopy, with a tungsten-filament atom-reservoir (TFAR), hollow-cathode lamps and limited-field viewing is described. The performance of this atom cell is compared with that of the carbon-filament atom-reservoir for deter... | 18,961,305 |
Acid-base equilibria in ethylene glycol--I: definition of pH and determination of pk-values of acid-base indicators. | A pH-scale in ethylene glycol is defined, based on potentiometric measurements for a cell without liquid junction: glass electrode || 0.1M (HCl + KCl), ethylene glycol | AgCl:Ag; and a potentiometric-spectrophotometric method for the determination of pK-value of acid-base indicators in ethylene glycol on the basis of t... | 18,961,308 |
Oxidation with permanganate in presence of fluoride potentiometric determination of manganese(II). | The effects of acidity, fluoride concentration, temperature and concentration of manganese in the reaction between KMnO(4) and Mn(II) were studied potentiometrically. The rate of reaction is increased by increasing the fluoride concentration and/or decreasing the acidity of the solution. The formal redox potentials of ... | 18,961,313 |
Simultaneous determination of N-unsubstituted- and N-substituted nitroazoles and criteria for their identification-I Nitroimidazoles and nitropyrazoles-polarographic determination. | The N-unsubstituted nitroazoles have an imino hydrogen atom in contrast to the N-substituted derivatives, and react with hydroxide to give nitroazole anions. The strongly negative shift of E(1 2 ) for these anions makes possible simultaneous polarographic determination of any pair of compounds, one of which is an N-uns... | 18,961,314 |
Complexation of polyvinyl acetate with iodine. | Polyvinyl acetate and iodine form a characteristic red complex in the presence of potassium iodide. Spectrophotometry of the complex at 510 nm in a methanol-water system at 20 degrees yields linear calibration curves over the range 25-100 mg of polyvinyl acetate per 1. of final solution. The limit of detection is 0.1 m... | 18,961,316 |
The performance characteristics of analytical methods-III. | The range of concentrations covered by an analytical method is an important performance-characteristic, and suggestions are made for definition of this range. The ability to detect small concentrations are also considered, and it is suggested that the standard deviation of blank determinations be quoted as the performa... | 18,961,338 |
Determination of Hg(II) in acidic media by stripping voltammetry with collection. | Stripping voltammetry with collection at a rotating ring-disk electrode having a platinum ring and a glassy-carbon disk was used for the determination of Hg(II) in 1.0M H(2)SO(4) medium in the range 0.10-4.00 ppM. Satisfactory results were obtained only after a thin film of Au (two monolayer equivalents) was electropla... | 18,961,350 |
Aromatic sulphonate ion-selective electrode membrane with crystal violet as ion-exchange site. | Four triphenylmethane derivatives (cations) and a high molecular-weight quaternary ammonium ion were used as the ion-exchange site in the liquid membranes of electrodes responsive to aromatic sulphonate ions, such as benzenesulphonate and alpha-naphthalenesulphonate. The nitrobenzene or 1,2-dichloroethane membrane cont... | 18,961,356 |
Determination of lithium stearate in sebacate-based lubricants by atomic absorption. | An accurate method is proposed for the determination of lithium stearate in sebacate-based lubricants. The sample is treated with dilute hydrochloric acid and an extraction is performed with ethyl ether to remove di-isopropyl phosphite which would otherwise interfere by causing the subsequent precipitation of lithium p... | 18,961,363 |
NMR determination of the microscopic constants of diprotonated diamines in aqueous solution. | The microscopic acidity constants of the diprotonated asymmetric N-methyl-substituted ethylenediamines and N-methylpiperazine were determined by using the change of the chemical shift of the methyl protons with varying acidity. The determination was carried out at 25 degrees in aqueous solution and in an ionic medium o... | 18,961,374 |
Interpretation of mass spectra. | A computer programme is described which calculates the mass numbers and the relative intensities of each of the lines in the cluster formed in a mass spectrometer from a single type of fragment ion which contains one or more polyisotopic elements. Many elements such as B, C, S, Cl and Br possess more than one naturally... | 18,961,381 |
Indirect flame-photometric determination of silicon. | An indirect flame-photometric method for the determination of silicon in terms of the potassium in precipitated K(2)SiF(6) has been developed. Optimum conditions have been found for the precipitation and the washing of the precipitate with aqueous ethanol. Satisfactory results have been obtained for silicon contents &g... | 18,961,383 |
Coulometric microdetermination of peroxides--I. Hydrogen peroxide. | An electroanalytical method, based on controlled-potential coulometry in the iodine-iodide system, has been developed for determination of small amounts of hydrogen peroxide. The sample is added to an electrolyte containing an acid solution of iodide and the iodine, which is produced rapidly, is reduced at a rotating p... | 18,961,387 |
Selective separation of uranium from other elements by cation-exchange chromatography in hydrobromic acid and hydrochloric acid-acetone mixtures. | U(VI) can be separated from Ga, Fe(III), Bi, Pb, Cd, Zn, Cu(II) and Au(III) by quantitative elution with 0.50M HBr in 86% acetone or with 0.35M HBr in 90% acetone from a column of AG50W-X4 cation-exchange resin of 200-400 mesh particle size. U(VI) and many other ions are retained. U(VI) then can be eluted selectively w... | 18,961,390 |
Determination of vanadium and molybdenum by atomic-absorption spectrophotometry. | A method is described for the determination by atomic-absorption spectrophotometry of vanadium and molybdenum, up to the milligram level, in samples of yellow cake, uranium-bearing minerals and geochemical standards. After attack with acids these two elements are separated from each other and from matrix elements by me... | 18,961,392 |
Solvent extraction-spectrophotometric determination of rare earths with chlorophosphonazo-III. | The rare-earth chlorophosphonazo III chelates are easily extracted from an aqueous solution (pH 1.1-1.5) into n-butanol. The absorbance at the absorption maximum (at 668 nm) is about 3 times that in aqueous solution. The spectrophotometric determination of rare earths has been investigated. | 18,961,422 |
Evaluation of 1-(2-thiazolylazo)-2-hydroxy-3-naphthoic acid as a metallochromic indicator. | The acid dissociation constants of 1-(2-thiazolylazo)-2-hydroxy-3-naphthoic acid (TAHN) and the formation constants of Cu(II), Ni(II) and Zn(II) chelates of this dye have been determined spectrophotometrically at 25 degrees in a 5% v/v mixture of dioxan and water. The formation constants of the 1:2 chelates are smaller... | 18,961,425 |
Rapid EDTA determination of lead in binary alloys of lead and tin. | Binary alloys of lead and tin were dissolved in nitric acid (1 + 1) containing 10% sodium fluoride. The tin(IV) was effectively masked by the fluoride. The lead was quickly and accurately titrated with EDTA in a hexamine-buffered solution, with Xylenol Orange as indicator. | 18,961,427 |
Detection and spectrophotometric determination of cobalt with dimedone dioxime. | Dimedone dioxime forms coloured complexes only with cobalt, nickel and copper ions in alkaline solution. Acidification and solvent extraction enables cobalt (1-50 mug) to be determined spectrophotometrically without interference. A specific spot test for cobalt is based on the same reaction. | 18,961,442 |
The error in absorption measurements caused by the use of non-monochromatic light-III Application to linear calibration curves. | When in spectrophotometry the absorption is measured with non-monochromatic light, a curved calibration curve is often obtained. Some errors are introduced if a linear calibration curve is still used. The magnitude of these errors has been calculated. | 18,961,446 |
Stepwise a.c. amperometric titration of cadmium and zinc with EGTA. | The theory of d.c. and a.c. amperometric titrations based on complexometric reactions is presented. It is shown that when E(1 2 )(M(I)) > E(1 2 )(M(II)) and log K(M(I)L) < log K(M(II)L), M(I) and M(II) can be sequentially determined by d.c. as well as a.c. amperometric titration. If, on the other hand E(1 2 )(M(I... | 18,961,447 |
Rapid determination of the equivalence volume in potentiometric acid-base titrations to a preset pH-II Standardizing a solution of a strong base, graphic location of equivalence volume, determination of stability constants of acids and titration of a mixture of two weak acids. | A newly proposed method of titrating weak acids with strong bases is applied to standardize a solution of a strong base, to graphic determination of equivalence volume of acetic acid with an error of 0.2%, to calculate the stability constants of hydroxylammonium ion, boric acid and hydrogen ascorbate ion and to analyse... | 18,961,474 |
Applications of enzyme-catalysed reactions in trace analysis-VII Determination of lead and indium by their inhibition of isocitrate dehydrogenase. | The inhibition of isocitrate dehydrogenase by lead, indium and calcium has been studied. Methods for the determination of 0.024-1 mug of lead and indium, based on this inhibition, are outlined. Lead may be separeted from some interfering ions by extraction with tributyl phosphate in isobutyl methyl ketone, before appli... | 18,961,476 |
Comparison between amperometric and true potentiometric end-point detection in the determination of water by the Karl Fischer method. | A rapid and sensitive method using true potentiometric end-point detection has been developed and compared with the conventional amperometric method for Karl Fischer determination of water. The effect of the sulphur dioxide concentration on the shape of the titration curve is shown. By using kinetic data it was possibl... | 18,961,491 |
Katalytische bestimmung von silberspuren in wabetariger lösung und nach extraktion. | The application of the catalysed oxidation of Bromopyrogallol Red by potassium per- sulphate for silver determination is discussed. In aqueous solution silver concentrations of 0.5- 1 mug/ml can be determined and 1- 13 ng/ml in the presence of 1, 10-phenanthroline as activator. In combination with solvent extraction, c... | 18,961,494 |
Phase-titration analysis of ternary mixtures containing mutually miscible components. | A method, based on phase-titration, for the analysis of ternary mixtures composed of mutually miscible components is described. One of the components is determined by an independent chemical or physical means and its concentration in the original mixture then brought to a fixed value by adding a calculated amount of on... | 18,961,497 |
Polystyrene impregnated with beta-diphenylglyoxime, a selective reagent for palladium. | alpha- and beta-diphenylglyoximes impregnated on macroreticular polystyrene (XAD-2) were tested as adsorptive reagents and one of them (the beta-isomer) was found to adsorb palladium in preference to platinum (selectivity factor 20) and nickel (factor > 100). | 18,961,503 |
Preparation, properties and analytical application of thorium n-phenyl-o-nitrobenzohydroxamate. | A new complex of thorium(IV) with N-phenyl-o-nitrobenzohydroxamic acid (PNHA) has been prepared by reacting an aqueous solution of thorium with an alcoholic solution of PNHA at 60 degrees C and adjusting the pH to 4-4.5. The infrared spectra and thermal analysis of the complex are discussed. The use of PNHA for gravime... | 18,961,504 |
[Not Available]. | The method for the determination of sulphur in organic compounds (E. Debal and R. Levy, Bull. Soc. Chim. France, 1968, 426; 1971, 3374) by combustion in oxygen at 1310-1320 degrees C and coulometric titration of the sulphur dioxide formed is improved. Silver and 8-hydroxy-quinoline are successfully used to remove halog... | 18,961,505 |
Spectrophotometric determination of iron in sea-water by solvent extraction as the ternary complex iron(II)-2-nitroso-4-chlorophenol-rhodamine B. | Iron has been determined in sea-water by extraction of the ternary complex of iron(II) with 2-nitroso-4-chlorophenol and Rhodamine B at pH 4.7 and measurement at 558 nm. Toluene is used as the organic solvent. Any iron(III) is reduced with hydroxylammonium chloride. | 18,961,509 |
Complexation reactions of pyridinols. | Complexation of iron(III) with several pyridinols has been studied and used in selective detection and determination (spectrophotometric and chelatometric) of the metal. Iron(III)-pyridinol complexes are also used as indicators in acid-base titrations. A thiol group vicinal to a phenol group in a pyridine molecule prov... | 18,961,528 |
Thiomercurimetric determination of sulphur, aliphatic and aromatic thiols and disulphides in hydrocarbon solvents, using reduction with sodium aluminium bis(2-methoxyethoxy)dihydride. | A method is proposed for determination of hydrogen sulphide and aliphatic and aromatic thiols in hydrocarbon solvents by extraction with 2M potassium hydroxide and titration with o-hydroxymercuribenzoic acid in the presence of dithiofluorescein and dithizone, with selective masking with acrylonitrile. Sulphur and organ... | 18,961,530 |
Redox indicator properties of some substituted chrysoidins. | Indicator properties of eleven substituted chrysoidins have been studied. Conditional reduction potentials of the three appreciably reversible indicators in this group were obtained by classical approaches and by use of a potentiopoised standard solution procedure. Chemical and electrochemical observations lead to the ... | 18,961,544 |
Study of ion-association complexes used in spectrophotometric determination of iron. | The following ion-association systems were investigated spectrophotometrically: Fe(2,2'-bipyridyl)(3)(Methyl Orange)(2); Fe(1,10-phenanthroline)(3)(Methyl Orange)(2); Fe(4,7-diphenyl-1,10-phenanthroline)(3)(Methyl Orange)2; Fe(1,10-phenanthroline)(3)(Benzyl Orange)2; Fe(4,7-diphenyl-1,10-phenanthroline)(3)(Benzyl Orang... | 18,961,549 |
Atomic-emission spectrometry with an induction-coupled high-frequency plasma source Comparison with the inert-gas shielded premixed nitrous oxide-acetylene flame for multi-element analysis. | The performance for trace analysis in solution by atomic-emission spectrometry from a 36-MHz induction-coupled radiofrequency plasma atom-cell is predicted from a simple model and compared with the corresponding characteristics of an inert-gas shielded nitrous oxide-acetylene flame. A longer linear calibration range is... | 18,961,578 |
On the reduction of oxygen in aqueous solution by electrolytically precipitated cadmium. | The reduction of oxygen in aqueous solution by electrolytically precipitated cadmium, used in a reductor column, has been studied in two ways. First, by analysis of the effluent for the hydrogen peroxide formed as a reaction intermediate, the conditions for quantitative reduction have been found. Attention is called to... | 18,961,595 |
Comparison of an instrumental and modified Kjeldahl technique for determination of nitrogen in niobium and tantalum alloys. | Results obtained for the determination of nitrogen in two tantalum alloys and six niobium alloys by modified Kjeldahl and Leco TC-30 nitrogen-oxygen determinator are compared. In the 5-25 ppm range, for tantalum alloys, the relative standard deviation was 3-9% by the Kjeldahl procedure and 9-11% by the instrumental tec... | 18,961,607 |
Controlled potential lodometric determination of nitrate after reduction to nitrite by coppered cadmium. | A controlled-potential coulometric iodometric method previously developed for the accurate determination of small amounts of nitrite has been extended for the determination of nitrate after its reduction on a coppered cadmium reductor. The conditions for quantitative reduction have been investigated with respect to typ... | 18,961,612 |
Gravimetric determination of selenium from perchloric acid solution with hydrazine. | The gravimetric determination of selenium, by reduction of selenious acid in perchloric acid solution with hydrazine hydrate, has been studied in detail. Elemental selenium is completely precipitated in 3.2-5.1M perchloric acid at room temperature or 100 degrees C. One mole of selenious acid reacts with one mole of hyd... | 18,961,615 |
New redox titrants in non-aqueous or partially aqueous media-V Potentiometric titrations with iodosobenzene diacetate in acetic acid medium. | A stable new redox titrant, viz., iodosobenzene diacetate in anhydrous acetic acid medium, is proposed for the potentiometric determination of a number of reductants such as As(III), I(-), Fe(II), N(2)H(4), [Fe(CN)(6)](4-), Tl(I), Sb(III), hydroquinone, ascorbic acid, phenol, aniline and oxine. | 18,961,616 |
The use of 5-(4-pyridyl)nonane for the separation of chromium(vi) from fission products in hydrochloric acid media. | The distribution of chromium(VI) between 5-(4-pyridyl)nonane in benzene and hydrochloric acid media has been studied as a function of the concentration of the acid, extractant, chromium(VI), chloride and a few other ions. The extraction mechanism and the composition of the extracted complexes of Cr(VI) have been propos... | 18,961,632 |
A study of some pyridylazo dyestuffs as chromogenic reagents and the elucidation of the nature of their metal complex spectra. | A series of dyestuffs having the same basic structure as 2-(2-pyridylazo)-5-diethyl-aminophenol (PADAP) but varying in their substituents on the 5-positions of both rings has been prepared. Dissociation constants for three such dialkylaminophenol derivatives have been determined, the pK(OH) values being of the same ord... | 18,961,644 |
Direct photometric titration of tellurium. | A direct photometric titration method has been developed for the determination of tellurium. Tellurium(IV) is titrated with potassium dichromate in 2-6M nitric acid (or 1-4M perchloric acid) at 380-430 nm (blue-violet filter). Selenium(IV) does not interfere. | 18,961,646 |
Advantages of statistical design in the investigation of titrimetric methods, as exemplified by a factorial-experiment study of the ferric iron-ascorbic acid titration system. | An example is outlined of the application of factorial experiment-design to the development of a titrimetric method, and the usefulness of such designs to analytical chemistry is discussed. | 18,961,652 |
A stable d.c. capillary arc plasma for solution analysis. | The analytical capability of a d.c. capillary arc plasma, operating on argon, is described. Solutions containing Cd, Pb, Hg, I, As and Zn are introduced into the plasma from a tantalum-filament atomizer. Signals are observed from both the arc and the tail-flame. The problem of sample rejection by the hot plasma is illu... | 18,961,653 |
Acid-base equilibria in ethylene glycol--II: autoprotolysis constants and acid-base properties of ethylene glycol and its mixtures. | The acid-base behaviour of ethylene glycol and its mixtures with water (1, 5 and 10%), methanol, ethanol, isopropanol, nitromethane (each 10%) and ethyl methyl ketone-chloroform (5 + 5%) have been investigated by potentiometric titration, in a cell without liquid junction, equipped with a glass and a silver-silver chlo... | 18,961,676 |
Polarographic reduction of methylene blue in presence of clay minerals. | Clay-Methylene Blue suspensions have been examined polarographically. The degree of binding of the dye on the clay particles has been calculated. The possibility of using the data in estimating the clay content of a sample and identifying the mineral is suggested. | 18,961,669 |
Colour changes of chemical indicators-VI: metallochromic indicators for direct chelometric titrations of zinc. | Eriochrome Blue SE, Eriochrome Red B, Naphthylazoxine 6S, SNAZOXS, and Zincon have been studied in order to find optimum conditions for their use as metallochromic indicators in direct visual chelometric titrations of zinc. The sharpness of the indicator transitions has been investigated by means of photometric titrati... | 18,961,678 |
Spectrographic determination of impurities in ultrapure tungsten and tungsten oxide. | The effects of an external magnetic field and of the diameter of the anode on the spectroscopic line intensity of the impurity elements in ultrapure tungsten and tungsten oxide have been studied. The results obtained are used for the development of a more sensitive method for the determination of these impurities (Mn, ... | 18,961,672 |
3-methyl-2-oxazolidone as a solvent for acid-base titrations. | 3-Methyl-2-oxazolidone has been evaluated as a solvent for the titration of various weak carboxylic acids and phenols. Its high dielectric constant and wide liquid range contribute to its outstanding solvent properties. Tetrabutylammonium hydroxide was the titrant. End-points were determined potentiometrically with a g... | 18,961,698 |
The analysis of detergents. | A review is made of the analysis of detergents, covering the determination of all classes of component materials. | 18,961,702 |
Atomic-absorption determination of manganese, cobalt and copper in whole blood and serum, with a graphite atomizer. | A new and rapid method is described for the determination of Mn, Co and Cu by atomic absorption with a graphite atomizer and deuterium compensation, on very small samples of whole blood and serum, with no preliminary manipulations. The metal concentrations in blood serum from healthy donors have been found to be Mn 9 +... | 18,961,710 |
The use of long-chain alkylamines for preconcentration of traces of molybdenum, tungsten and rhenium in their determination by atomic-absorption spectroscopy-I General studies. | Long-chain alkylamines are used for the preconcentration of traces of molybdenum, tungsten and rhenium as thiocyanate complexes, in their determination by atomic-absorption spectroscopy. General studies of factors, influencing the extraction show that the thiocyanate complexes can be extracted into chloroform containin... | 18,961,721 |
Basicity of nitropyrazoles and their simultaneous spectrophotometric determination. | The protonation constants of some 1-, 3(5)-, 3-, 4- and 5-nitropyrazoles have been determined, and compared with those of nitroimidazoles. The effect of the position of the nitro group in the pyrazole and imidazole ring is discussed. The ortho effects of the nitro group in pyrazole and imidazole are compared and found ... | 18,961,738 |
Spectrophotometric determination of tungsten in ores and steel by chloroform extraction of the tungsten-thiocyanate-diantipyrylmethane complex. | A method for determining up to about 6% of tungsten in ores and mill products is described. It is based on the extraction of the yellow tungsten(V)-thiocyanate-diantipyrylmethane ion-association complex into chloroform from a 2.4M sulphuric acid-7.8M hydrochloric acid medium containing ammonium hydrogen fluoride as mas... | 18,961,741 |
Spectrophotofluorometric determination of some alkaloids containing a tertiary amine group. | The method developed involves the base-catalysed condensation of mixed anhydrides of organic acids, where a tertiary amine group functions as the basic catalyst. The product of the condensation reaction is highly fluorescent and allows the fluorometric determination of alkaloids containing a tertiary amine group, in th... | 18,961,745 |
An evaluation of solvent mediators for ion-selective electrode membranes based on calcium bis(dialkylphosphate) sensors trapped in poly(vinyl chloride) matrices. | This study on several alkan-1-ols, di-n-octylphenyl phosphorate and di-n-nonyl phthalate as solvent materials in ion-selective electrode membranes based on calcium bis(dialkylphosphate) sensors trapped in a PVC matrix indicates that the best electrodes are made with di-n-octylphenyl phosphonate. These are selective for... | 18,961,752 |
Utilization of an Hg(2+)-sensitive membrane-electrode in the complexometric determination of Bi(3+), Fe(3+) and Cr(3+). | The paper reports the results obtained in the complexometric determination of Bi(3+), Fe(3+) and Cr(3+) by using an Hg(2+)-sensitive membrane-electrode for the end-point indication. The determination of Bi(3+) and Fe(3+) is performed after addition of mercuric complexonate from which these cations release Hg(2+) by mea... | 18,961,754 |
Chromatography of aromatic compounds on anion-exchange resins. | Complex mixtures of aromatic compounds can be rapidly separated on anion-exchangers in the acetate form with acetic acid as eluent and determined automatically by recording the absorbance in the ultraviolet. Carboxylates are separated by ion-exchange. Hydrogen bonds between non-disso-ciated acids and the counter-ions i... | 18,961,772 |
Sequential determination of thorium and rare earths with EDTA and kojic acid. | Kojic acid can be used instead of acetylacetone to form a ternary complex with Th-EDTA that is more stable than the corresponding Xylenol Orange ternary complex, thus making it possible to titrate lanthanides with EDTA at pH 5.5 after titration of thorium at pH 2. | 18,961,798 |
Trace characterization of powders by atomic-absorption spectrometry: the state of the art. | A review is made of the progress achieved in the last 15 years in the field of trace characterization of powders by direct atomic-absorption spectrometry. The studies covered include the development of novel atomization devices, modification of existing atomic-absorption spectrometers, and the use of closed-cavity vapo... | 18,961,816 |
Studies on synthetic inorganic ion exchangers-V: preparation, properties and ion-exchange behaviour of amorphous and crystalline thorium tungstate. | Amorphous and crystalline thorium tungstate have been prepared by mixing 0.1M thorium nitrate and 0.1M sodium tungstate under different conditions. The physico-chemical properties, chemical stability, composition, TGA, DTA, X-ray, infrared absorption and ion-exchange behaviour of thorium-tungstate are reported and disc... | 18,961,820 |
Miniature potassium-sensitive electrodes with neutral carriers in a poly(vinyl chloride) matrix. | A miniature version of the potassium ion-selective electrode with valinomycin or dimethyldibenzo-30-crown-10 in a poly(vinyl chloride) matrix is described. Electrodes having an effective membrane area of <0.2 mm(2) exhibit Nernstian behaviour within a range of activities of the potassium ion of 10(-1)-10(-5)M, a rap... | 18,961,826 |
An evaluation of four titrimetric methods for the determination of lead in ores. | Four titrimetric methods for the determination of lead in ores were evaluated. In the absence of bismuth and indium, a method based on EDTA titration of lead, after chloroform extraction of lead diethyldithiocarbamate, yields accurate and more precise results than the other methods evaluated. Interference from indium c... | 18,961,829 |
Trace analysis for chlorinated hydrocarbons in air by quantitative combustion and coulometric chloride determination: application to standardization of vinyl chloride permeation tubes. | Methods for high-temperature combustion of vinyl chloride in air were studied theoretically and two types of gas mixtures were found to give 100% conversion into HCl. The chloride was determined by coulometric titration with silver, in 70% acetic acid. Good agreement between theoretical and experimental results was obt... | 18,961,836 |
Relative sensitivity coefficients for the analysis of steel by spark-source mass-spectrometry. | Quantitative analysis by spark-source mass-spectrometry requires the knowledge of socalled sensitivity coefficients for the elements being determined. Five series of analyses have been carried out on five different steel standard reference materials (NBS-SRM 661-665), using photoplate detection. The relative sensitivit... | 18,961,876 |
On the copper(II)-EDTA-par system for visual and photometric end-point detection in iron(III)-EDTA titrations. | The copper(II)-EDTA-PAR system is proposed as indicator for direct EDTA titration of 0.2-20 mg of iron(III) in acetic acid medium. The precision and accuracy have been evaluated by spectrophotometric titration. Microtitrations determine down to 10 mug of iron. A logarithmic concentration diagram has been constructed to... | 18,961,892 |
Metal oxide electrodes as sensors in complexometric titrations. | EDTA titrations of lead and manganese, and of some other ions by using these as indicator ions, have been followed potentiometrically with PbO(2) and MnO(2) electrodes. Explanations are put forward for the anomalies observed in the titration curves. With the MnO(2) electrode, formation of an Mn(III)-EDTA complex is res... | 18,961,911 |
Semimicro determination of mercaptans with copper(II). | A rapid and precise titrimetric method for the determination of mercaptans on the semimicro scale is described. Samples dissolved in water, methanol. dimethylformamide or acetonitrile are treated with a measured excess of cupric sulphate. After 1 min, the excess of copper(II) is back-titrated with standard mercaptoacet... | 18,961,968 |
Accuracy of analysis of steels by use of a spark-source mass spectrometer with electrical detection. | The precision and accuracy of spark-source mass spectrometry with electrical detection has been studied, with five steel standard reference materials (NBS-SRM 661-665). Two different modes of analysis have been evaluated, magnetic scanning with electrical detection of the individual ions in sequence, using the total io... | 18,961,984 |
Ion-exchange separation and atomic-absorption determination of fifteen major, minor and trace elements in silicates. | A scheme of ion-exchange separation of fifteen elements (major, minor and trace) determined mainly by atomic-absorption spectrophotometry (Ti by colorimetry) is applied to rock, mineral and ceramic analysis. Mn, Cu, Co, Fe and Zn are separated on an anion-exchanger and Li, Na, K, Mg, Ca, Sr, Ti, Al, Ni and Ba on a cati... | 18,962,010 |
Acid-base titrations by stepwise addition of equal volumes of titrant with special reference to automatic titrations-IV Photometric titration of an acid. | In Part I of this series, evaluation methods for potentiometric titrations of acids performed by stepwise addition of titrant were introduced. These methods are non-approximative and may therefore in principle be applied to titrations of acids of any strength. This paper demonstrates that photometric titrations perform... | 18,962,034 |
Differential pulse polarography of some benzodiazepines and their determination in urine. | A differential pulse polarographic method has been applied to the determination of diazepam, oxazepam, nitrazepam and flurazepam down to 2 x 10(-7)M (0.14 mug/ml). The method can also be used with biological materials such as urine, without prior extraction. Only a 2-ml volume of urine is necessary. | 18,962,046 |
Chemical separation and spectrographic estimation of rare earths and yttrium in PuO(2) and (U,Pu)O(2). | An emission spectrographic method for the estimation of rare-earth impurities in plutonium oxide and the mixed oxide (U,Pu)O(2) (30% PuO(2)-70% UO(2)) has been developed. Rare-earth impurities are separated from the matrix by solvent extraction with tri-n-octylamine in xylene and are estimated after concentration. Thul... | 18,962,048 |
Anion-exchange behaviour of metals on deae-cellulose in hydrochloric acid-acetic acid media. | The anion-exchange behaviour of 35 metal ion species on a weakly basic cellulosic ion-exchanger (DEAE-cellulose) in mixed hydrochloric acid-acetic acid media has been investigated. The sorption of metal chloro-complexes on DEAE-cellulose is greatly enhanced with increasing concentration of acetic acid. Differences in s... | 18,962,056 |
Contributions to the basic problems of complexometry-XXVI determination of calcium in the presence of large amounts of magnesium. | Two methods for the determination of calcium in the presence of very large amounts of magnesium are proposed. Both are based on back-titration of excess of EGTA, Thymolphthalexone being used as indicator. In the one method the titrant is a zinc solution, in the other a calcium solution is used, with a small amount of z... | 18,962,059 |
Rapid determination of nitrate nitrogen in soils. | A simple but effective method for pretreatment of soil samples is suggested. The application of an electrodynamic vibrator or ultrasonic device eliminates the necessity for continuous stirring in direct potentiometric determination of nitrate nitrogen. It also makes the extraction process faster, and the apparatus coul... | 18,962,068 |
Direct atomic-absorption spectrometric analysis of geological materials-a review. | A review is given of the problems likely to be encountered in the atomization of solid samples of geological materials, and of the applications of this technique. | 18,962,084 |
Spectrophotometric determination of some penicillins with ammonium vanadate. | A spectrophotometric method for determining some penicillins has been developed. A known volume of the penicillin solution-in phosphate buffer of pH 6.8 is boiled with ammonium vanadate solution-in sulphuric acid medium-for 10 min and the absorbance of the colour formed is measured at 750 nm. The excess of vanadate can... | 18,962,095 |
High-precision gravimetric coulometry using the silver-perchloric acid coulometer: Titration of arsenious oxide with electrogenerated iodine. | High-precision gravimetric coulometry with a silver-perchloric acid coulometer is evaluated as an alternative to the conventional titrimetric method. The loss of weight (caused by electrolytic dissolution) of a highly pure silver anode in series with the cathode of a conventional constant-current titration system is me... | 18,962,104 |
Estimation of methionine and its metal complexes by oxidation with chloramine-T and dichloramine-T. | A simple method for the estimation of methionine (HMt) in aqueous solution has been developed, based on its oxidation with chloramine-T and dichloramine-T at room temperature. The direct titration, with visual or potentiometric end-point involves a two-electron change, corresponding to the formation of methionine sulph... | 18,962,124 |
[Not Available]. | The sample (up to 5 mg) is destroyed by using a wet process in a glass flask of the Kjeldahl type. Aluminium cobalt, tin and iron are determined spectrophotometrically. The following reactions are used: complexation of aluminium by Alizarin Red S and calcium cobalt(II) by tiron tin(IV) by phenylfluorone, iron(III) by t... | 18,962,127 |
Analytical application of organic reagents in hydrophobic gel media-IV Selective preconcentration of Cobalt(II) with 1-nitroso-2-naphthol gel. | Cobalt is selectively extracted from solution onto gel beads impregnated with 1-nitroso-2-naphthol. A concentration factor of 67 has been achieved by passing 2 litres of sea water containing 0.05 ppm of cobalt over the beads at a flow-rate of 40 ml/hr. The cobalt is eluted from the beads with methyl isobutyl ketone. | 18,962,134 |
A new ion-exchange test for detection of ketones on the microgram scale. | A test for the detection of certain ketones is based on the reaction with 1-chloro-2,4-dinitrobenzene in the presence of an anion-exchange resin in the OH(-) form, to give a violet colour on the resin bead surface. | 18,962,137 |
Microscopic acid dissociation constants of 3,4-dihydroxyphenylpropionic acid and related compounds, and 3,4-dihydroxyphenylalanine (DOPA). | The dissociation constants of 3,4-dihydroxyphenylpropionic acid and related compounds and of DOPA were determined by potentiometric titration and complementary tristimulus colorimetry at 25 degrees and mu = 0.1 (NaClO(4)) in aqueous solution. The thermodynamic parameters were calculated from the values of the dissociat... | 18,962,144 |
[Not Available]. | Metal phosphorothioates are titrated in acetone, acetonitrile and dimethylformamide with potassium hydroxide, with potentiometric detection. They can be titrated in the presence of the corresponding phosphorothioic acids in the dimethylformamide. | 18,962,148 |
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