Abstract
The proposed method consists of four procedures; excess iodine for reactions with thiosulfate and/or sulfite under Procedures I, II and III, and the thiocyanate formed under Procedure IV are measured spectrophotometrically after proper chemical treatments. The absorbance obtained by Procedure I corresponds to the sum of the amount of tetrathionate and that of thiosulfate in the mixture. The absorbance obtained by Procedure II corresponds only to the amount of thiosulfate in the mixture. The absorbance obtained by Procedure III corresponds to the sum of the amount of thiosulfate and twice that of sulfite in the mixture. The absorbance obtained by Procedure IV corresponds to the sum of the amount of both thiosulfate and trithionate and twice that of tetrathionate in the mixture. The proposed method was applied to the determination of tetrathionate, thiosulfate, sulfite and trithionate mixed in various ratios in amounts of more than 0.05μmol with an error below ±0.02μmol.
