Use of iodine, iodates, periodate or dichromate in the potentiometric determination of dithionite and disulphite

ABSTRACT

A new potentiometric method is reported for the accurate determination of dithionite and disulphite using iodine, iodate, periodate, or dichromate. When iodine is used as oxidant the iodide produced is determined by titration with mercury [II] nitrate solution. When iodate, periodate or dichromate are used as oxidants a known excess of the oxidant is used, then after reaction a known excess of iodide solution is added and unreacted iodide is determined by titration with mercury [II] nitrate solution. All end points were determined potentiometrically using silver amalgam standard calomel electrodes. Potential breaks averaged 322 and 383 mV/0.1 ml for titrants for dithionite and disulphite determinations respectively and were sharp enough for precise determination of end points over a wide range of concentrations and even with low concentrations of the analysts