Thiosulfate is a reducing agent. It is routinely used as a titrant to determine concentrations of oxidants such as hypochlorite in bleach and dissolved oxygen in water. It instantly dechlorinates water, and is used to stop bleaching action in the paper-making industry. Thiosulfate forms water-soluble complexes with many metals, making it useful in photoprocessing (where it dissolves excess silver bromide on the surface of exposed film, preventing excessive darkening). Thiosulfate is also useful in the extraction of silver from silver ore, in leather manufacture, and as a mordant in the textile industry.
|Structure of the thiosulfate ion.|
Yellow = sulfur, Red = oxygen.
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(ammo hypo, Amthio
|high||fungicide; fixative in photographic development; lubricants for metalworking; metal cleaning agent|
|BaS2O3||barium thiosulfate||slight||manufacture of explosives and matches; photographic processes|
|high||liquid lime/sulfur agricultural treatments|
|AuNa3(S2O3)22 H2O||gold(I) sodium thiosulfate dihydrate
(Auricidine, Aurocidin; Aurolin; Auropex;Auropin; Aurosan; Aurothion)
|high||screening for gold allergies; antirheumatic|
|K2S2O3||potassium thiosulfate||high||fixative in photographic development; liquid lime/sulfur agricultural treatments|
|high||fixative in photographic development; water dechlorination; paper manufacture; whitening agent|
Solubility data compiled from the CRC Handbook of Chemistry and Physics (CRC). Commercial and medical uses compiled from the Merck Index (Merck) and Web/paper references cited below.
S2O32- + AgBr(s) AgS2O3- + Br-
S2O32- + AgS2O3- Ag(S2O3)3-
HOCl + 2 S2O32- Cl- + S4O62- + OH-
CN- + S2O32- SCN- + SO32-This reaction is catalyzed by an enzyme produced by cell mitochondria to neutralize small quantities of ingested cyanide (which occurs naturally in cassava root, lima beans, and almonds!).
Thiosulfate is an intermediate in several biochemical pathways, including the synthesis of L-cysteine (an amino acid). Thiosulfate is manufactured by some cells by oxidation of elemental sulfur and by degradation of L-cysteine.
S8 + 8 SO32- 8 S2O32-
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Last Revised 06/11/07.URL: http://antoine.frostburg.edu/chem/senese/101/compounds/print-thiosulfate.shtml