What is thiosulfate used for?
Most of thiosulfate’s usefulness stems from its ability to convert certain insoluble metal compounds into soluble complexes, and its ability to act as a mild reducing agent. • Photographic fixing agent. An emulsion of sodium thiosulfate (called hypo by photographers) is used to stop development of exposed film. Thiosulfate converts undeveloped silver bromide grains in the film into water-soluble silver thiosulfate complexes that can be removed when the film is washed. S2O32- + AgBr(s) AgS2O3- + Br- S2O32- + AgS2O3- Ag(S2O3)3- • Extracting silver from ores. Thiosulfate’s ability to convert silver compounds into soluble silver complexes also makes it useful in ore processing. • Paper manufacture and dechlorination of water. Thiosulfate ion is used to remove chlorine (hypochlorite) from water or from solutions used to bleach paper pulp: HOCl + 2 S2O32- Cl- + S4O62- + OH- • Dissolved oxygen testing and chemical analysis of oxidants. Thiosulfate is a reducing titrant used for determining ma
