Its used as a fixer (hypo) in photography to dissolve unexposed silver halides as an antidote for cyanide poisoning and in water treatment to neutralize chlorine. Additional roles include gold extraction analytical chemistry and paper manufacturing.

Its primary purpose is acting as a reducing agent and complexing agent enabling dechlorination detoxification and selective dissolution in industrial and medical processes.

Sodium thiosulfate (NaSO) is an inorganic salt often found as a white translucent pentahydrate (NaSO5HO) with molar mass around 248 gmol. It features a tetrahedral thiosulfate anion where a central sulfur bonds to three oxygens and one terminal sulfur showing high water solubility and a monoclinic crystal structure.