Sulfidolysis of Tetrathionate and Spectrophotometric Determination of Tetrathionate, Thiosulfate and Sulfide in Their Mixtures

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Abstract
A spectrophotometric method has been developed for the determination of tetrathionate, thiosulfate and sulfide in mixtures. The conditions for tetrathionate to be stoichiometrically converted to thiosulfate were established by varying reaction time, reaction temperature, pH and amount of sulfide. The present method consists of three procedures: I, II and III. The absorbance obtained by Procedure I corresponds to the sum of the thiosulfate and twice the tetrathionate in the mixture. The absorbance obtained by Procedure II, where tetrathionate was not sulfitolyzed and sulfide was removed, corresponds to the amount of thiosulfate only. The absorbance obtained by Procedure III corresponds to the sum of the amount of thiosulfate and twice that of sulfide. The method is applicable to the determination of tetrathionate, thiosulfate and sulfide in amounts more than 0.1μmol and gave a relativestandard deviation of 1.2% at 1μmol level of tetrathionate in the presence of 1μmol of sulfide and 2μmol of thiosulfate.