Noun
A salt of thiosulphuric acid; -- formerly called hyposulphite.
Source: Webster's dictionaryAs with chlorine or iodine solutions, sodium thiosulphate (or any soluble thiosulphate) is an effective reagent for reducing bromine to colorless odorless bromide. Source: Internet
He had discovered in 1819 that sodium thiosulphate was a solvent of silver halides, and in 1839 he informed Talbot (and, indirectly, Daguerre) that it could be used to "fix" silver-halide-based photographs and make them completely light-fast. Source: Internet