thiosulfurous acid

Thiosulfurous acid (HS-S(=O)-OH) or sulfurothionous O,O acid is a low oxidation state (+1) sulfur acid [ (+1) is the average oxidation state of the two structurally different sulfur atoms . The exterior atom has a oxidation number of (-1) while the central sulfur atom has the oxidation state of (+3) ]. It is termed a disulfur(I) acid. It is the equivalent acid for disulfur monoxide. Thiosulfurous acid is formed by reacting hydrogen sulfide and sulfur dioxide at room temperature. The thiosulfurous acid molecule is unstable when condensed, reacting with itself.