A. Berka

Oxidation of organic substances by tervalent manganese compounds: VIII. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of hexaquomanganese(III) ion in perchloric acid

Abstract The reaction of hexaquomanganese(III) ion with hydroquinone, p-aminophenol, metol, pyrocatechol, resorcinol, and phloroglucinol was studied. It has been found that the first three substances are oxidized quantitatively with the exchange of two electrons to the corresponding quinone compounds and that this reaction can be employed for direct or indirect titrimetric determination of these substances. On the other hand, pyrocatechol, resorcinol, and phloroglucinol are oxidized nonstoichiometrically with a deeper destruction of the aromatic system, which prevents analytical use of these reactions.

Investigation of the formal redox potentials of the system Pb4+/Pb2+ with regard to the use of lead tetraacetate in volumetric analysis

Abstract The values of the formal redox potential of the system Pb4+/Pb2+have been measured in media of hydrochloric acid; perchloric acid and acetic acid (also with the addition of potassium acetate). The dependence of the formal redbx potential value on the concentration of the acids mentioned, on the concentrations of the Pb4+ and Pb2+ ions in the solution, and on time, has been investigated.

Destruction of carcinogens in laboratory wastes: I. Destruction of benzidine, o-tolidine, and o-dianisidine by permanganate

Abstract A suitable method for destruction of carcinogenic amines (benzidine, o -tolidine, and o -dianisidine) in laboratory wastes has been developed. The method is based on the oxidation of these substances with permanganate in sulfuric acid medium and affords better than 99.8% decontamination for all three substrates tested.

The use of redox reactions in the analysis of dyes and dye intermediates: XIV. Direct current polarography of 4,4′-disubstituted azobenzenes in acetonitrile

Abstract The polarographic reduction of some 4,4′-disubstituted azobenzenes in an acetonitrile medium was studied. The diffusion character of the observed limiting currents was confirmed and a mechansim of polarographic reduction proposed. The possibility of analytical application is briefly discussed.

The oxidation of benzidine, o,o′-tolidine and o,o′-dianisidine by manganese dioxide

Abstract The oxidation of benzidine, o,o ′-tolidine, and o,o ′-dianisidine by manganese dioxide was studied in an acidic medium. It has been shown that the studied substances are quantitatively oxidized by the reagent to the corresponding quinonediimines and that this reaction can be utilized for the indirect titrimetric determination of benzidine and o,o ′-tolidine, based either on ferrometric titration of unconsumed manganese dioxide or on ascorbinometric titration of the quinonediimine formed.

Potentiometric oxidimetric determination of ruthenium with lead tetraacetate

Summary It has been established that tetravalent ruthenium is oxidized in a medium of perchloric acid at room temperature by lead tetraacetate to Ru(VII) oxide. Under suitable conditions this reaction is immediate and quantitative, so that it may be employed for a precise Potentiometrie determination of ruthenium. By using a 0.1N lead tetraacetate solution it is possible to determine 5–15 mg. Ru in the acidity range 0.03–0.1N HClO4 at room temperature by direct titration. A 0.05N solution of the reagent may be used to determine 2–10 mg. Ru in ti volume of 50 ml.

The use of redox reactions in the analysis of dyes and dye intermediates: XV. Direct current polarography of some water-insoluble azo pigments in acetonitrile

Abstract The polarographic behavior of five water-insoluble azo pigments was studied in an acetonitrile medium. The diffusion character of the observed limiting currents was confirmed and a mechanism was proposed for the polarographic reduction. The possibility of an analytical application is briefly discussed.

The analysis of dyes and dye intermediates by physico-chemical methods: I. Thin-layer chromatographic and spectrophotometric behavior of some azobenzene derivatives

Abstract Thin-layer Chromatographic behavior of 14 azobenzene derivatives was studied, suitable eluents were found, and the R f values were determined. Spectrophotometric behavior of these substances in acetonitrile was studied, as well as the influence of acids and bases on the studied spectra. The validity of the Lambert—Beer law in a concentration region from 1 × 10 −5 to 7 × 10 −5 was verified.

Oxidation of organic substances with compounds of trivalent manganese: XXIII. Preparation, stability, and determination of the titer of standard solutions of the fluoride complex of trivalent manganese

Abstract A method of preparation of 10−2 −10−3M standard solutions of the fluoride complex of manganese(III) by the reaction of manganese(II) with permanganate in a medium of potassium fluoride acidified with sulfuric acid has been developed. It has been found that in a medium of 1 M sulfuric acid, 0.5 M manganese(II) sulfate, and 0.1 M potassium fluoride these solutions are sufficiently stable for both direct and indirect titrimetric determinations. The titer was determined using potassium iodide as a primary standard and potentiometric, bipotentiometric, or biamperometric titration.

The use of redox reactions in the analysis of dyes and dye intermediates: XVI. The influence of proton donors on direct current polarographic behavior of 4,4′-disubstituted azobenzenes in acetonitrile☆

Abstract The influence of water and perchloric acid on the polarographic behavior of 4,4′-disubstituted azobenzene derivatives in acetonitrile has been investigated. The conditions were defined for the polarographic determination of the test substances in acetonitrile containing various concentration of water. The presence of strong acids prevents analytical use of these reactions.