Redox Indicators In Titrations Research Articles

Azine Dyes as Redox Indicators in Titrations with Chloramine

Azine Dyes as Redox Indicators in Titrations with Chloramine

Redox indicators in titrations with chloramine-T

Naphthidine, 3,3'-dimethylnaphthidine disulphonic acid, o-dianisidine, di-phenylbenzidine, quinoline yellow, amaranth, methyl red, methyl orange, rhodamine-B and erioglaucine-A are examined as indicators in macro-and micro-titrations of arsenic(III), antimony(III), ascorbic acid, hydroquinone, metol, hydrazinium sulphate, isonicotinic acid hydrazide, semicarbazide hydrochloride and phenylhydrazine hydrochloride with chloramine-T. The indicators give sharp colour changes under optimal conditions. Transition potentials are reported.

N-substituted phenothiazines as redox indicators in titrations with chloramine-T and chloramine-B

Profenamine hydrochloride, fluphenazine dihydrochloride, trifluopromazine hydrochloride, cyamepromazine maleate, perphenazine dihydrochloride and mepazine hydrochloride are proposed as redox indicators in the titration of hydroquinone, metol and ascorbic acid with chloramine-T and chloramine-B in sulphuric, hydrochloric and acetic acid media. They give a sharp reversible colour change at the equivalence point. A simple but accurate method for the determination of hydroquinone, metol and ascorbic acid is described. The conditional potentials and molar absorptivities of the indicators and redox potential of chloramine-B are reported.

Redox indicators in titrations with dichloramine-B

Naphthidine, dimethylnaphthidine, dimethylnaphthidinedisulphonic acid, o-dianisidine, Quinoline Yellow, diphenylbenzidine and Amaranth are proposed as indicators in titrations of arsenic(III), iron(II), antimony(III), hydroquinone, hydrazinium sulphate, phenylhydrazine hydrochloride, semicarbazide hydrochloride and ascorbic acid with dichloramine-B. They give a very sharp colour change at the equivalence point. Arsenic(III) and iron(II) are suggested for standardization of dichloramine-B solutions. A potentiometric method for the determination of arsenic(III) and semicarbazide hydrochloride is described.

Naphthidines and o-dianisidine as redox indicators in titrations with N-bromosuccinimide

The optimum conditions for the successful use of naphthidine, 3,3′-dimethyl-naphthidine, 3,3′-dimethylnaphthidinedisulphonic acid and o-dianisidine as indicators in macro- and micro-titrations of hexacyanoferrate(II), iron(II), hydroquinone, metol and ascorbic acid with N-bromosuccinimide have been established. The indicators give a very sharp reversible colour change at the equivalence point and have advantages over the existing redox indicators. Hydrazinium sulphate and hydroxylammonium chloride have been determined indirectly. Anhydrous hexacyanoferrate(II) and iron(II) are suggested for the standardisation of N-bromosuccinimide solutions.

N-substituted phenothiazines as indicators in titrations with chloramine-T

Trifluoperazine dihydrochloride, butaperazine dimaleate, promethazine hydrochloride, diethazine hydrochloride, prochlorperazine maleate and chlorpromazine hydrochloride have been studied as redox indicators in titrations of hydroquinone, metol and ascorbic acid with chloramine-T. The end-points obtained are sharper than with conventional indicators. The molar absorptivities of the oxidized indicators are reported. Simple but accurate methods for the determination of hydroquinone and metol are described.

Naphthidines as redox indicators in titrations with vanadate

Naphthidine, naphthidinedisulphonic acid, 3,3'-dimethylnaphthidine and 3,3'-di-methylnaphthidinedisulphonic acid have been studied as redox indicators in titrations with vanadate. Sharp colour changes are obtained at the equivalence points in titrations of 0.05—0.01 N solutions of iron(II), hydroquinone, molybdenum(V) and uranium(IV) under appropriate conditions of acidity with oxalic or phosphoric acid as indicator catalyst. The transition potentials are reported.

N-substituted phenothiazines as redox indicators in titrations with N-bromosuccinimide

Butaperazine dimaleate, trifluoperazine dihydrochloride, diethazine hydrochloride, promethazine hydrochloride, prochlorperazine maleate and chlorpromazine hydrochloride are proposed as redox indicators in the macro- and micro-titration of hydroquinone, Metol (N-methyl-4-aminophenol sulphate) and ascorbic acid with N-bromosuccinimide in hydrochloric, sulphuric and acetic acids. They give very sharp and reversible colour changes at the equivalence point. A simple titrimetric method for the determination of hydroquinone, Metol and ascorbic acid and a potentiometric method for the determination of Metol are described.

Redox indicators in titrations in aqueous nitric acid

Iron(II) in nitric acid solution can be titrated with dichromate (and vice versa), diphenylamine, N-phenylanthranilic acid, ferroin, or brucine being used as indicator. Fluoride is added when one of the first three is used, and urea if the last is used. Citric, oxalic and tartaric acids, arsenic(III) and mercury(I) interfere in the titration.

Reversible indicators for titrations with hypochlorite

Several sulphone-phthalein indicators have been examined to test their possible application as redox indicators in titrations with hypochlorite, bromate, iodate and chloramine-T. It was confirmed that Cerana's indicator, Bromothymol Blue, is an excellent reversible indicator for titrations with hypochlorite. Bromocresol Purple is possibly slightly better. Cresol Red, Xylenol Orange, Thymol Blue and Methyl Thymol Blue are also suitable, but there is little point in using them, because the first two are converted to Bromocresol Purple and the last two to Bromothymol Blue. In the remaining systems the indicators were inferior to or no better than conventional indicators.

Triphenylmethane dyes as oxidation-reduction indicators in titrations with cerium (IV) perchlorate

1. It has been shown that erioglaucine A, eriogreen B and xylene cyanol FF function excellently as internal indicators in the titration of iron(II), uranium(IV), oxalic acid and hydroquinone by ceric ammonium nitrate in 0.5–4 N perchloric acid medium. The titrations can be done with the normal speed, the dyes indicating the equivalence point sharply and accurately. The indicator reactions involved in the titrations have been found to be reversible. 0.5 ml of a 0.1% aqueous solution of the dye is sufficient for 50–100 ml of the titration mixture. The dye which has an yellow colour in acid solution turns to an orange red sharply on the addition of a slight excess of the cerium(IV) salt solution. The indicator correction is practically negligible with 0.1 N or 0.05 N solutions of the cerium salt. The indicator correction amounts to 0.1 ml of 0.01 N cerium(IV) salt solution. These dyes do not function satisfactorily in the titration of vanadium(IV) and molybdenum(V) with ceric ammonium nitrate in perchloric acid medium. 2. The use of triphenyl methane dyes as redox indicators in titrations with cerium(IV) perchlorate is a great convenience, because the other two indicators available for the purpose, nitroferroin and rutheniumdipyridyl, are costly.