A new method for the iodometric determination of sulphoxides

A method is described for determination of sulphoxides through their reaction with iodide in a trifluoroacetic acid/acetone medium to produce iodine, which is then titrated with thiosulphate.     

A new volumetric method for the determination of molybdenum(VI)

Summary A new volumetric method has been developed for the determination of molybdenum(VI). The method consists in the reduction of molybdenum(VI) by heating with a slight excess of hydrazine sulphate in 1 to 2 M hydrochloric acid medium for ten minutes on a water bath. The mixture is cooled and the molybdenum(V) obtained determined by titration with a standard solution of ceric sulphate at an overall acidity of 4 N hydrochloric acid, using diphenyl benzidine as indicator and adding 5 ml of syrupy phosphoric acid for 50 ml of the mixture. Alternately the molybdenum(V) can be titrated with a standard solution of ceric sulphate at an overall acidity of 3 N hydrochloric acid using ferroin as indicator and adding 5 ml of syrupy phosphoric acid for 50 ml of the titration mixture. The molybdenum(V) can also be titrated with a standard solution of sodium vanadate in 8 N sulphuric acid medium, using N-phenyl anthranilic acid as indicator. Alternately, the titration with sodium vanadate can be made with diphenyl benzidine as indicator in 4 N acid medium, adding 5 ml of syrupy phosphoric acid and 1 ml of 1.0 M oxalic acid to catalyse the indicator action. The method now proposed is much more convenient than the methods currently available. It is simple because it does not require any costly chemicals or complicated apparatus. Furthermore, it has the advantages of great rapidity and excellent precision.     

A new volumetric method for the determination of uranium(VI)

Summary A new volumetric method for the estimation of uranium(VI) salt based on its photoreduction in the presence of diethyl ether has been developed. The recommended procedure consists of exposing uranium(VI) solution in about 1 N sulphuric acid solution with an excess of saturated aqueous ether solution in a glass vessel to the light from a Phillips repro lamp or sun light for 1 hour. The uranium(IV) salt formed is estimated by titration with a standard solution of sodium vanadate.The reduction does not proceed to uranium(III) stage under any conditions of exposure. Fluoride, phosphate, arsenate and perchlorate are not found to interfere either with the photochemical reduction or with the subsequent oxidimetric titration. But chloride and bromide ions markedly inhibit the photochemical reaction.     

A rapid volumetric method for the determination of beryllium in beryls and associated minerals

A new volumetric method has been proposed for the determination of beryllium in beryls and associated minerals. The method involves the direct precipitation of beryllium as BeNH₄PO₄.6H₂O in presence of complexone II, dissolving the precipitate in dilute perchloric acid and titrating the liberated phosphate with standard bismuthyl perchlorate. Results for samples agree within ± 0.2% of the standard values.     

A microanalytical volumetric method for the determination of antimony in lead-base and tin-base alloys

Indications are given for the constructions of simple and efficient immersion filters and bicarbonate valves.The authors have elaborated a rapid and exact microvolumetric method for the determination of antimony in alloys based on lead or tin, containing up to 18% antimony.     

A new gas volumetric determination of the nitrate ion

The gas volumetric determination is based on the thermal decomposition of ammonium nitrate which is carried out in a fused ammonium hydrogensulphate—ammonium sulphate mixture placed in a two-step reactor. The method is easily applicable for the analysis of solid inorganic nitrates, and can also be used for solutions.     

Further development in the high-precision volumetric method for the determination of uranium in nuclear-grade uranium compounds

The high-precision uranium determination by reduction with ferrous sulfate in phosphoric acid and titration with dichromate, which is applicable to nuclear-grade uranium compounds in which the uranium exists nearly exclusively as U(IV), has been modified. The modification enlarges the range of applicability of the original method to include the analysis of uranium compounds in which the uranium exists as U(VI) or as a mixture of U(IV) and U(VI), such as U₃O₈. The modified method has the same precision, relative freedom from interferences and applicability for routine use as the original method.     

A new volumetric method for microdetermination of tellurium or mercury

Summary A volumetric method for the determination of tellurium(IV) or mercury(II) in the mg range is proposed by using the redox process. Reduction is effected by boiling with an excess of reducing sugar in alkali solution. The metals obtained are re-oxidised by means of ferric chloride solutions. The ferrous ions formed are titrated against a standard solution of ceric sulphate using N-phenyl anthranilic acid as indicator. The interference due to various cations has been investigated.

---

Zusammenfassung Ein neues oxydimetrisches Verfahren zur Bestimmung von Tellur(IV) oder von Quecksilber(II) im Milligrammaßstab wird vorgeschlagen. Die mit einem Überschuß von reduzierendem Zucker in alkalischem Milieu bei Siedehitze reduzierten Metalle werden mit Eisen(III)-chlorid reoxydiert. Das dabei entstandene Eisen(II) wird mit Cersulfat gegen N-Phenylanthranilsäure als Indikator titriert. Die Störung durch verschiedene Kationen wurde untersucht.

     

A modified volumetric method for the estimation of streptomycin sulphate in pharmaceuticals

Summary A volumetric method for the estimation of streptomycin sulphate in pharmaceuticals is based on the quantitative discharge of the violet colour of the maltol-iron complex, produced when streptomycin is hydrolysed in alkaline medium and treated with ferric chloride, by potassium permanganate. It is simple, accurate and other antibiotics such as dihydrostreptomycin, sodium salt of benzyl penicillin, chloramphenicol do not interfere. Procain penicillin has to be separated by extractio with chloroform.

---

Zusammenfassung Die beschriebene volumetrische Streptomycinbestimmung in Arzneimitteln beruht auf dem Abbau des Streptomycins in alkalischer Lösung zu Maltol, Bildung des Maltol-Eisen(III)-Komplexes und Titration mit Permanganat bis zur Entfärbung. Das Verfahren ist einfach auszuführen und gibt Werte von befriedigender Genauigkeit. Dihydrostreptomycin, Chloramphenicol sowie das Natriumsalz des Benzylpenicillins stören nicht. Procain-Penicillin muß vorher durch Extraktion mit Chloroform abgetrennt werden.

     

A routine method for the determination of retronecine

A method for the routine determination of the necine base retronecine from biological matrices is described, using gas chromatography for quantification. The biological matrices studied included blended sheep whole rumen fluid and bacterial growth media. The structurally similar compound 2,6-dimethoxypyridine was utilized as an internal standard. Prior to gas chromatography, the bis(heptafluorobutyrate) derivatives of both compounds were formed. The relative percent recoveries of retronecine and the internal standard were 73% and 82%, respectively. The detection limit of retronecine in blended whole rumen fluid was found to be 0.09 μg/mL, and 0.02 μg/mL in bacterial growth media. The precision of the peak area ratio (retronecine to internal standard) was 10% from blended whole rumen fluid, and 14% from bacterial growth media. This method was used to analyze samples from viable cultures incubated with retronecine. Received: 6 May 1997 / Revised: 29 September 1997 / Accepted: 2 October 1997     

A spectrophotometric method for the determination of nickel

A photometric method for the determination of nickel using versene is described. Up to 20 mg of nickel can be determined with a maximum deviation of ± 0.10 mg. The effect of interfering elements, concentrations, accuracy and limitations of the method are discussed.     

A colorimetric method for the determination of nitrazepam

A simple colorimetric method for the determination of nitrazepam is described. Nitrazepam dissolved in ethyl alcohol (95%) produces a yellow anion on addition of aqueous sodium hydroxide, and this is measured spectrophotometrically. The method has been applied to pharmaceutical formulations containing nitrazepam.     

A catalytic method for the determination of acetonitrile

A kinetic method for the determination of micro quantities of acetonitrile, based on its catalytic activity on the oxidation of pyrocatechol violet by hydrogen peroxide, is presented. On the basis of the results obtained by kinetic investigations, a kinetic equation as well as the apparent rate constant of this reaction is given. Acetonitrile was determined by the application of the differential form of the tangent method in concentrations ranging from 1.52 × 10^?3M to 22.8 × 10^?3M, with relative standard deviation up to 6%.     

A biamperometric method for the determination of sulfate

A biamperometric method for the determination of sulfate has been developed. Its application to the determination of sulfate content in rubidium uranium trisulfate is discussed. Sulfate is determined by titration with lead nitrate in aqueous ethanolic medium using ferrocyanide-ferricyanide redox system as biamperometric indicator. Initially, the method has been tested for standard. K₂SO₄ solutions. In case of Rb₂ U(SO₄)₃, since uranium interferes, it is precipitated as ammonium diuranate and excess ammonia is removed prior to the titration. Precision of better than 0.3% was achieved with no significant bias.     

A spectrophotometric method for the determination of nitrite

Nitrite reacts with dichromate quantitatively under suitable conditions of temperature and acid concentration. A linear relationship was found to exist between nitrite concentration and the absorbance at 580 nm of the chromium (III) species produced. This was used to determine the nitrite. The influence of a number of ions on the determination of nitrite was investigated; up to 100-fold excess nitrate has no influence on the determination of nitrite.