THE DECOMPOSITION OF AQUEOUS DITHIONITE AND ITS REACTIONS WITH POLYTHIONATES SNO62-(N = 3-5) STUDIED BY ION-PAIR CHROMATOGRAPHY

Aqueous dithionite decomposes at 20-degrees-C and pH values not far from 7.0 to give thiosulfate and sulfite from which trithionate may form. Addition of thiosulfate accelerates this reaction only at pH < 6. The pH dependence is explained by formation of HS2O3- ions which arc reduced by dithionite to HS- and SO32-. Sulfide destroys dithionite by nucleophilic cleavage, probably with formation of sulfoxylate and thiosulfite ions. The polythionates SnO62- (n = 3-5) are reduced by dithionite at pH = 7.0 and 20-degrees-C according to SnO62-+S2O42- +2H2O --> S2O32- +Sn-3SO32- +4H+ + 2SO32-The reaction rate rapidly increases with the number n of sulfur atoms. In secondary reactions sulfite attacks SnO62- ions with thiosulfate formation.