Spectrophotometric determination of micro amounts of thiosulfate by liberation of thiocyanate from mercury(II) thiocyanate

Abstract

The proposed determination of thiosulfate is based on the liberation of thiocyanate by the reaction of thiosulfate with mercury(II) thiocyanate and spectrophotometric determination of the thiocyanate with iron(III). The reaction of thiosulfate with mercury(II) thiocyanate is elucidated with reference to a system containing phosphate buffer; the phosphate is shown to participate directly in the reaction, and a balanced chemical equation is given. Optimum conditions are described for the stoichiometric formation of 3 mol of thiocyanate from 1 mol of thiosulfate. The method can be applied to the determination of thiosulfate in the range 3 × 10 −6–1.4 × 10 −4 M (1.7–78.5 μg thiosulfate in 5 ml).