Dithionic acid, H2S2O6, is the inorganic compound with the formula H2S2O6. It is the doubly protonated derivative of dithionate, a well-characterized dianion. Dithionic acid is mainly observed and characterized as an aqueous solution.
Synthesis
Dithionates can be made by oxidizing a sulfite (from the +4 to the +5 oxidation state), but on a larger scale they are made by oxidizing a cooled aqueous solution of sulfur dioxide with manganese dioxide:
2 MnO2 + 3 SO2 → MnS2O6 + MnSO4The manganese dithionate solution formed can then be converted to dithionate salts of other metals by metathesis reactions:
Ba2+ (aq) + MnS2O6 (aq) + MnSO4 (aq) → BaSO4 (s)↓ + BaS2O6 · 2 H2O (aq)Concentrated solutions of dithionic acid can subsequently be obtained treating a barium dithionate solution with sulfuric acid:
BaS2O6 (aq) + H2SO4 (aq) → H2S2O6 (aq) + BaSO4 (s)↓See also
- Sodium dithionite
- Hypophosphoric acid, the phosphorus equivalent.
References
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. pp. 715-716 978-0-08-037941-8 ↩