Ammonium thiosulfate

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Ammonium thiosulfate
Ammonium thiosulfate.svg
CAS number 7783-18-8 YesY
PubChem 6096946
ChemSpider 4807475 YesY
Jmol-3D images Image 1
Molecular formula H8N2O3S2
Molar mass 148.21 g mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Ammonium thiosulfate (ammonium thiosulphate in British English) is an inorganic compound. It is white crystalline solid with ammonia odor, readily soluble in water, slightly soluble in acetone and insoluble in ethanol and diethyl ether.[1]


Photographic fixation[edit]

Ammonium thiosulfate is used in photographic fixer. It is a so-called rapid fixer, acting more quickly than sodium thiosulfate fixers.[2] Fixation involves these chemical reactions (illustrated for silver bromide):[3]

AgBr + 2 (NH4)2S2O3 → (NH4)3[Ag(S2O3)2] + NH4X
AgBr + 3 (NH4)2S2O3 → (NH4)5[Ag(S2O3)3] + NH4X

Extractive metallurgy[edit]

Ammonium thiosulfate is also used for leaching of gold and silver. It works with presence of copper as a catalyst here. This process is a less nontoxic alternative gold cyanidation.[4]


It can be used as an fertilizer.[5] As suggested by some research studies it can be used as an additive to coal-waste mixtures to reduce formation of very dangerous dioxins and furans.[6]

See also[edit]


  1. ^ MSDS - Ammonium Thiosulfate
  2. ^ Praní černobílých filmů a papírů
  3. ^ Karlheinz Keller et al. "Photography" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a20_001
  4. ^ Thiosulfate leaching of gold — A review
  5. ^ Minerální hnojiva se sírou
  6. ^ Ekologický monitor. Krátké zprávy ze zahraničních periodik – 19.1.2006