Titrimetric determination of vanadium(IV) with cerium (IV)sulphate at room temperature using ferroin as indicator

A procedure has been developed for the visual titrimetric determination of vanadium(IV) with cerium(IV) sulphate, using ferroin is redox indicator. The method has been extended to the determination of iron(II) and vanadium(IV) in mixtures.     

Titration of oxalic acid with cerium sulphate at room temperature using ferroïn as internal indicator

Evidence is presented to show that, contrary to the statements of earlier workers, the reaction between ceric sulphate and oxalic acid is quite rapid in hydrochloric acid medium specially in the presence of iodine monochloride as catalyst. We have now found that the need for a temperature of 50° in the cerimetric titration of oxalic acid using ferroïn as indicator is not due to the sluggishness of the reaction between oxalic acid and Ce^IV (as believed by Willard and Young) but because of the slow reaction between oxidised ferroïn and oxalic acid in the presence of sulphate ion derived from eerie sulphate. Conditions have now been developed for the titration of oxalic acid with eerie sulphate at room temperature in lN hydrochloric acid medium using ferroïn as indicator, and barium ion as scavenger for sulphate ion, which latter markedly retards the reaction between oxalic acid and oxidised ferroïn, as well as that between oxalic acid and Ce^IV. The method now developed has several advantages over that prescribed by Willard and Young because it avoids the high temperature of 50°, where the ferroïn indicator is found to undergo some dissociation. It also avoids the use of the iodine monochloride catalyst.     

Titration of vanadium(IV) with cerium(IV) sulphate, with ferroin as indicator, in aqueous alcohol as a facile reaction medium

A new procedure for the titration of vanadium(IV) with cerium(IV) sulphate, with ferroin as indicator, in aqueous alcohol medium, is reported. The visual titration gives accurate results but potentiometric titration fails in this medium; this failure is attributed to the sluggish indicator electrode behaviour. Experimental conditions for preliminary quantitative photochemical reduction of vanadium(V) with alcohol have been established.     

Titrimetric determination of vanadium (IV) with potassium permanganate at the room temperature, using phosphoric acid as catalyst and ferroin as internal indicator

Summary The observation that the reaction between vanadium(IV) and potassium permanganate is catalyzed by ortho phosphoric acid at the room temperature has been utilized to develop a new procedure for the titrimetric determination of vanadium(IV). In the absence of chromium(III) and other coloured ions the end point can be detected making use of the colour of permanganate itself, and applying the necessary correction. This procedure cannot, however, be employed for titrations with 0.01 N potassium permanganate when the use of ferroin must be resorted to indicate the end point. The use of ferroin in macro titrations helps to eliminate the correction and the interference of coloured ions like chromium(III) up to a reasonable limit. Titrations without the use of the ferroin indicator can be carried out within a wider range of acidity viz. 0.1 N to 1.0 N.

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Zusammenfassung Ein neues Verfahren zur titrimetrischen Bestimmung von Vanadium-(IV) wird auf den katalytischen Einfluß gegründet, den Orthophosphorsäure bei Zimmertemperatur auf die Reaktion zwischen V^IV und KMnO₄ ausübt. Bei Abwesenheit von Cr^III und anderen gefärbten Ionen kann der Endpunkt durch die Eigenfarbe des Permanganats festgestellt werden, wobei eine Korrektur erforderlich ist. Für kleinere Vanadiumgehalte (Titration mit 0,01 n KMnO₄-Lösung) wird die Verwendung von Ferroin als Indicator empfohlen, wobei die Notwendigkeit einer Korrektur sowie der Einfluß störender Ionen bis zu bestimmten Grenzen vermieden wird. Titrationen ohne Indicator können bei einem Säuregehalt von 0,1 n–1 n ausgeführt werden.

     

Titration of vanadium(IV) with cerium(IV) sulphate, with ferroin as indicator, in aqueous acetone as facile reaction medium An analytical and mechanistic study

A new procedure for the titration of vanadium(IV) with cerium(IV) sulphate, with ferroin as indicator, in aqueous acetone medium is reported. A differential determination of iron(II) and vanadium(IV) is also possible. A probable mechanism for the fast ferriin-vanadium(IV) reaction in acetone medium is given.     

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.     

Titrimetric assay of ofloxacin in pharmaceuticals using cerium(IV) sulphate as an oxidimetric reagent

Two titrimetric methods which are simple, rapid, cost-effective and eco-riendly are described for the determination of ofloxacin (OFX) in bulk drug and in tablet formulations based on the oxidation of OFX by Ce(IV) sulphate. In direct titrimetry (method A), the acidified solution of OFX is titrated directly with Ce(IV) sulphate using ferroin as indicator, and indirect titrimetry (method B) involves the addition of known excess of Ce(IV) sulphate to an acidified solution of OFX followed by the determination of unreacted oxidant by back titration with ferrous ammonium sulphate (FAS) using the same ferroin indicator. In both the methods, the amount of Ce(IV) sulphate reacted corresponds to OFX concentration. Method A and method B permit the determination of OFX over the concentration range of 1.5?C15 mg in both the methods and the quantitation is based on a 1: 5 reaction stoichiometry (OFX: Ce (IV) sulphate). The methods were statistically evaluated by calculating percent relative error (% RE) for accuracy and percent relative standard deviation (% RSD) for precision, and were applied successfully to the determination of OFX in tablets with mean recoveries in the range of 96.50?C98.42%. No interference was observed from common additives found in pharmaceutical preparations. The accuracy and reliability of the methods were further ascertained by performing recovery tests s standard-addition technique.     

Titrimetric and spectrophotometric assay of pantoprazole in pharmaceuticals using cerium(IV) sulphate as oxidimetric agent

Titrimetric and spectrophotometric assay of pantoprazole sodium sesquihydrate (PSS) using cerium(IV) sulphate as the oxidimetric reagent is described. The methods are based on the oxidation of PSS with a measured excess of Ce(IV) sulphate followed by the determination of unreacted oxidant using different reaction schemes. In titrimetry, the unreacted oxidant was determined by back titration with ferrous ammonium sulphate (FAS) in sulphuric acid medium. Spectrophotometry involves the reduction of unreacted Ce(IV) sulphate with a fixed quantity of Fe(II). The resulting Fe(III) is complexed with thiocyanate and the absorbance is measured at 470 nm. In both the methods, the amount of Ce(lV) sulphate reacted corresponds to PSS concentration. Titrimetry is applicable over 1–10 mg range whereas in spectrophotometry, the calibration graph is linear in the range of 0.5–7.0 μg/mL and the calculated molar absorptivity value is 1.58 × 10⁵ L/mol cm. The validity of the proposed methods was tested by analyzing pure and dosage forms containing PSS. Statistical treatment of the results reflects that the proposed procedures are precise, accurate and easily applicable to the determination of PSS in pure form and in pharmaceutical formulations.     

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.     

Some triphenylmethane dyes as redox indicators in the titration of antimony(III) with cerium(IV) sulphate

Erioglaucine A, Eriogreen B, Patent Blue and Xylene Cyanol FF work satisfactorily for the titration of Sb(III) with Ce(IV) in 1-2N sulphuric acid medium with iodine as catalyst. In hydrochloric acid medium the colour of the oxidized dye is very evanescent but is very much improved in intensity and stability by the addition of manganese(II) sulphate; no catalyst is needed.