The determination of micro amounts of polythionates: Part VI. Spectrophotometric determination of ultramicro amounts of tetra-, penta- and hexathionate by cyanolysis and solvent extraction

A spectrophotometric determination of ultramicro amounts of tetra-, penta- and hexathionate is proposed. The method is based on extraction of a complex formed between methylene blue and thiocyanate (equivalent to the polythionates) with dichloroethane, and measurement of the absorbance of the organic phase. The conditions for all three polythionates to he completely converted into thiocyanate were established by varying the pH, temperature, reaction time, and amount of cyanide. The method is suitable for the determination of 3.3 10-7– l.0 10-5M tetrathionate, 1.7 10-7–5.0 10-6M pentathionate, and 1.0 10-7–3.3 10-6M hexathionate.