Use of alcoholic iodine in the potentiometric titration of quinol, hexacyanoferrate [II] and succinic acid dihydrazide

ABSTRACT

The present work is undertaken to ascertain the feasibility of applying the instantaneous reactions between alcoholic iodine and a given reductant to the direct determination of quinol, hexacyanoferrate [II] and succinic acid dihydrazide. A slight excess of alcoholic iodine is added to the reductant and the equivalent iodide is titrated with mercury [II] using silver amalgam as the indicator electrode. Some prior studies on the determination of reductants are instructive. Quinol [4was determined cerimetrically, amperometrically, iodimetrieally, mercurimetrically, and vanadatimetrically. Hexacyanoferrate [II] was determined by oxidation with cerium [IV] using N-phenylanthranilic acid as indicator, or with dichromate using oxazine dyes as redox indicator or argentimetrically using chromate as indicator or potentiometrically using dibromamine T as indicator and chelatimetrically byits precipitation with a known excess of Cu [II] and subsequent titration of the unconsumed Cu [II] with EDTA. Hydrazide was determined potentiometrically with NaN0[2], coloumetrically with generated cerium [IV] in acid medium, amperometrically with NaNO2 using two identical platinum micro-electrodes or detected by chromatography. The potentiometric titrations approach now developed has several advantages, including application to reductants over a wide range of concentrations, simplicity, rapidity, reproducibility and high accuracy. The potential breaks average 280 mV per 0.1 ml titrant