An Investigation of Errors in the Amperometric and Starch Indicator Methods for the Titration of Millinormal Solutions of Iodine andThiosulphate

Abstract

The amperometric method of Foulk and Bawden when applied to the titration of 0.001N thiosulphate solutions with iodine is shown to be more precise and to have a smaller " blank" than that using starch as indicator. With simple precautions the method has an accuracy of at least 0.1 per cent. over the range pH 1-8, but at higher pH there is serious error due to sulphate formation. The magnitudes of other errors are determined and it is shown that all can be rendered negligible in titrations of milli-normal solutions.