Thiosulfate is the anion S_{2O3^{2-. Thiosulfates are only stable in neutral or alkaline solutions, but not in acidic solutions, due to decomposition to sulfite and sulfur, the sulfite being expelled as sulfur dioxide:}}

S_{2O3^{2-(aq) + 2H+(aq) → SO2(g) + S(s) + H2O}}

This reaction is usually used to generate a temporary aqueous suspension to demonstrate diffraction of light in physics. If the light is shone from below, blue light is seen from above, and orange from sideways.

Uses of thiosulfates include the dissolving of silver salts from the photographic film.

See also

• Sodium thiosulfate

Thiosulfates | Oxoanions