Thiosulphate \Thi`o*sul"phate\, n. (Chem.) A salt of thiosulphuric acid; -- formerly called hyposulphite.

Note: The sodium salt called in photography by the name sodium hyposulphite, being used as a solvent for the excess of unchanged silver chloride, bromide, and iodide on the sensitive plate.

Source: Webster's Revised Unabridged Dictionary (1913)