tiosulfat

Thiosulfate, or tiosulfat in some languages, refers to the thiosulfate anion S2O3^2−. It consists of two sulfur atoms and three oxygens, with one sulfur bonded like in sulfate and the other in a reduced form. Common salts include sodium thiosulfate (Na2S2O3), potassium thiosulfate (K2S2O3), and ammonium thiosulfate ((NH4)2S2O3); these salts are typically highly soluble in water.

Industrial production of sodium thiosulfate generally involves the reaction of sodium sulfite with elemental sulfur in aqueous base: Na2SO3 + S → Na2S2O3. The thiosulfate ion can also arise from other sulfite-sulfur interactions under controlled conditions.

Thiosulfate is a mild reducing agent. In acidic solution, it decomposes to sulfur and sulfur dioxide: S2O3^2− + 2 H+ → S(s) + SO2 + H2O. It is widely used in iodometric titrations, where it reduces iodine to iodide, allowing quantitative analysis of oxidants. In photography, ammonium thiosulfate serves as a fixer to dissolve unexposed silver halide from developing emulsions. In water treatment, sodium thiosulfate is used to dechlorinate residual chlorine.

Medical and safety aspects: sodium thiosulfate is used as an antidote for cyanide poisoning, converting cyanide to thiocyanate via rhodanese-mediated metabolism. It can be employed as part of treatment regimens for certain poisonings and in laboratory medicine. Thiosulfate salts are generally of low toxicity but can irritate skin and eyes in concentrated forms; solutions should be handled with appropriate care, and acidic conditions can release irritating sulfur compounds.