The Decomposition of Aqueous Dithionite and its reactions with polythionates S n O 2− 6 (n = 3–5) studied by ion‐pair chromatography

Aqueous dithionite decomposes at 20°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 HS 2 O 3 − ions which are reduced by dithionite to HS − and SO 2− 3 . Sulfide destroys dithionite by nucleophilic cleavage, probably with formation of sulfoxylate and thiosulfite ions. The polythionates S n O 2− 6 (n = 3–5) are reduced by dithionite at pH = 7.0 and 20°C according to S n O 2− 6 + S 2 O 2− 4 + 2 H 2 O→S 2 O 3 2− + S n–3 SO 3 2− + 4H 1 + 2SO 3 2− The reaction rate rapidly increases with the number n of sulfur atoms. In secondary reactions sulfite attacks S n O 6 2− ions with thiosulfate formation.