Dithionate
The dithionate (or metabisulfate) anion, S
2O2−
6, is a sulfur oxoanion derived from dithionic acid, H2S2O6. Its chemical formula is sometimes written in a semistructural format, as [O3SSO3].
The sulfur atoms of the dithionate ion are in the +5 oxidation state due to the presence of the S–S bond. Generally dithionates form stable compounds that are not readily oxidised or reduced. Strong oxidants oxidise them to sulfates and strong reducing agents reduce them to sulfites and dithionites. Aqueous solutions of dithionates are quite stable and can be boiled without decomposition.