Titration of antimony(III) with cerium(IV) sulphate and diphenylamine and its derivatives as reversible indicators

Diphenylamine, barium diphenylamine sulphonate, N-phenylanthranilic acid and 2-nitrodiphenylamine have been investigated as reversible indicators for the titration of antimony(III) with cerium(IV) sulphate in 0.5–2 M sulphuric acid medium. Diphenylamine is the most satisfactory in titrations of antimony(III) in chloride-free solutions, e.g. of potassium antimonyl tartrate. Even low chloride concentrations affect the indicator action of N-phenyl-anthranilic acid or 2-nitrodiphenylamine, but diphenylamine is satisfactory in 1 M hydrochloric acid media. Iodine catalyst is necessary to accelerate the reduction of the oxidized indicator by antimony(III). The indicator colour change is vivid and the colour of the oxidized indicator is stable. Titrations of antimony(III) in mixtures with iron(II) and arsenic(III) are also considered.     

Sequential titration of iron(II) and vanadium(IV) mixtures with cerium(IV) sulphate, with ferroins as indicators

The titration of vanadium(IV) with cerium(IV) sulphate, with nitroferroin as indicator, is proposed. Unlike ferroin, the indicator does not need a catalyst in this system. By suitable choice of experimental conditions iron(II) can be titrated first to a ferroin end-point and then vanadium(IV) to a nitroferroin end-point.     

Radiometric redox titration of antimony(III) with potassium iodate

The redox titration of antimony(III), labeled with¹²⁵Sb(III), by potassium iodate was radiometrically investigated using the burette method and the standard series method. The stoichiometry of the redox process was determined. The redox valence (the number of equivalents per mol) of potassium iodate for the oxidation of antimony(III) to antimony(V) was found to be 6, differing from the results obtained using the usual visual indicator method, where the value was shown to be 4. This disagreement in the equivalents of potassium iodate for the oxidation of antimony(III) is discussed.     

A new spot test for cerium(IV) using triphenylmethane dyes

Summary A new sensitive and selective spot test for cerium(IV) using the triphenylmethane dyes, Erioglaucine A, Eriogreen B, Xylenecyanol FF, Setoglaucine O, and Setocyanine Supra, respectively, is described. The method consists of adding one drop of the dye solution (0.1%) to a drop of cerium(IV) solution, and then treating the mixture with sufficient amount of sulfuric, perchloric, or phosphoric acid to maintain the acidity at 6 to 9M. The colors produced with these dyes are: Erioglaucine A: orange, Eriogreen B: bright red, Xylenecyanol FF: orange yellow, Setoglaucine O: bright orange, and Setocyanine Supra: pink. The identification limit is 1 g in 1.5 ml, and the dilution limit is 11.5 · 10⁶ in all these cases. Many cations and anions do not interfere in the test, whereas reducing agents like Fe(II), Mo(V), U(IV), and hydroquinone, fluoride and EDTA interfere.

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Zusammenfassung Eine neue empfindliche und selektive Tüpfelnachweisreaktion für Cer(IV) mit den Triphenylmethanfarbstoffen Erioglaucin A (I), Eriogrün B (II), Xylolcyanol FF (III), Setoglaucin O (IV) bzw. Setocyanin Supra (V) wurde beschrieben. Man gibt einen Tropfen 0,1%ige Farbstofflösung zu einem Tropfen Cer(IV)-Lösung und behandelt die Mischung mit Schwefelsäure, Perchlorsäure oder Phosphorsäure, um 6 -bis 9-m Acidität zu erreichen. Die mit den genannten Farbstoffen erzielten Farbreaktionen sind: mit I orange, mit II leuchtend rot, mit IV leuchtend orange, mit III orange-gelb, mit V rosa. Die Erfassungsgrenze beträgt 1g/1,5 ml, die Grenzkonzentrationen in jedem Fall 11,5 · 10⁶. Viele Kationen und Anionen stören nicht, aber Reduktionsmittel wie Fe(II), Mo(V), U(IV), Hydrochinon sowie Fluorid und ÄDTA stören.

     

Tin(II) sulphate as a new reductimetric titrant--direct titration of thallium(III) with use of ion-pair and redox indicators

The use of tin(II) sulphate as a direct reductimetric titrant for thallium(III) has been investigated, with potentiometric and visual detection of the end-point. Some azure dyes are used as redox indicators and Methylene Blue is used as both a redox and an ion-pair indicator.     

Iron(II) titration of some metal ions, with oxazine dyes as redox indicators

The use of oxazine dyes as redox indicators in the determination of uranium(VI), copper(II), osmium(VIII), iridium(IV) and thallium(III) with iron(II) as reductimetric titrant in phosphoric acid medium has been investigated. The determination of copper in brass and the analysis of the binary mixtures of U(VI) and U(IV), and of Tl(III) and Tl(I) with this reductant and these indicators have been studied.     

Some observations concerning the direct titration of nitrite with cerium(IV)

Direct titration of nitrite with cerium (IV), with ferroin as indicator, is shown to give satisfactory results if the acidity is kept between 0.033 and 0.055M at the end-point. Loss of nitrous acid owing to volatilization and decomposition is discussed. From 10 to 60 mg of sodium nitrite can be estimated with a standard deviation of 5 mug and an average error of 0.2%.     

Inverse voltammetry of antimony with triphenylmethane dyes

A method is suggested for the determination of traces of antimony by inverse voltammetry of the solid phases formed with triphenylmethane dyes (Crystal Violet, Methyl Violet and Malachite Green) as the precipitants. The authors have studied the effect of concentration, adsorption and oxidation of the triphenylmethane dyes, potential and time of pre-electrolysis, and concentration of antimony(III) and some other elements on the polarogram shape and stripping current. A method for determining antimony traces in chromic salts is described as an example.     

Titrimetric determination of uranium (IV) with iron (III) using redox indicators

Summary Conditions have been established for the use of methylene blue, thionine and variamine blue as redox indicators in the titrimetric determination of uranium(IV) with iron(III) in an inert atmosphere at 98–100° C. Under the conditions prescribed, the method gives results with an accuracy of ±0.4%. The advantages of this method are discussed for the determination of uranium(IV) in the presence of iron(II).Methylene blue and thionine are more satisfactory than variamine blue, because variamine blue is not sufficiently stable at the necessary temperature, especially in hydrochloric acid medium.

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Zusammenfassung Die volumetrische Bestimmung von Uran(IV) mit Eisen(III) kann mit Hilfe von Methylenblau, Thionin oder Variaminblau als Redox-indicatoren in inerter Atmosphäre bei 98–100° C durchgeführt werden. Das Verfahren liefert unter den beschriebenen Bedingungen auf ±0,4% genaue Ergebnisse und ist besonders vorteilhaft für die Uran(IV)-be-stimmung in Gegenwart von Eisen(II). Variaminblau ist ungünstiger als die beiden anderen Indicatoren, da es bei der erforderlichen Tem-peratur nicht genügend stabil ist, besonders in salzsaurem Medium.

     

Some spectrofluorimetric applications of the cerium(IV)-cerium(III) system

Cerium(III) ions in dilute sulphuric acid medium exhibit a characteristic fluorescence which has its excitation maximum at 260 nm and its fluorescence emission maximum at 350 nm. By utilising the osmium-catalysed redox reaction between cerium(IV) and arsenic(III), microgram amounts of arsenic (7.5–37.5 μg) may be determined by spectrofluorimetric measurement of the ceriurm(III) produced. The principle may be applied to the determination of several other ions which cannot yet be determined by direct spectrofluorimetry, e.g.. Fe(II) (5.6–28 μg), oxalate (8.8–44μg). Osmium(VIII) (0.05–0.2 μg) and iodide (0.6–2.5 μg) may be determined by their catalytic action.     

Triphenylmethane dyes as redox indicators in dichrometry

Summary The use of some triphenylmethane dyes, Erioglaucine A, Eriogreen B, Xylenecyanol FF, Setoglaucine O, Setocyanine Supra, Fast Green FCF, and Night Blue as redox indicators in the dichrometric titration of iron(II), ferrocyanide, uranium(IV), molybdenum(V), and hydroquinone in hydrochloric acid, sulphuric acid and perchloric acid media has been studied. Conditions for the satisfactory titrations employing these indicators have been established.

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Triphenylmethanfarbstoffe als Redoxindicatoren bei Titrationen mit Dichromat

Zusammenfassung Bei der Titration von Eisen(II), Hexacyanoferrat(II), Uran(IV), Molybdän(V) und Hydrochinon mit Dichromat in salz-, schwefeloder perchlorsaurer Lösung wurden folgende Triphenylmethanfarbstoffe als Indicatoren verwendet: Erioglaucin A, Eriogrün B, Xylolcyanol FF, Setoglaucin O, Setocyanin Supra, Echtgrün FCF und Nachtblau. Die entsprechenden Titrationsbedingungen werden mitgeteilt.

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We are grateful to the Council of Scientific & Industrial Research, India, for the award of a Junior Research Fellowship to one of us (V. V. S. E. D.).