Ammonium thiosulfate

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Ammonium thiosulfate
Ammonium thiosulfate.svg
Names
IUPAC name
Diammonium thiosulfate
Other names
Ammonium thiosulphate, ATS
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.074
Properties
H8N2O3S2
Molar mass 148.20 g·mol−1
Except where otherwise noted, 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 with the formula (NH4)2S2O3. It is white crystalline solid with ammonia odor, readily soluble in water, slightly soluble in acetone and insoluble in ethanol and diethyl ether.[1]

Production[edit]

It is produced by treating ammonium sulfite with sulfur:[2]

(NH4)2SO3 + S → (NH4)2S2O3

Applications[edit]

Ammonium thiosulfate is used in photographic fixer. It is a so-called rapid fixer, acting more quickly than sodium thiosulfate fixers.[3] Fixation involves these chemical reactions (illustrated for silver bromide):[4]

AgBr + 2 (NH4)2S2O3 → (NH4)3[Ag(S2O3)2] + NH4Br
AgBr + 3 (NH4)2S2O3 → (NH4)5[Ag(S2O3)3] + NH4Br

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 nontoxic alternative gold cyanidation.[5] The advantage to ammonium thiosulfate is that the pyrolysis of its silver complexes leaves a residue solely of silver sulfide, in contrast to complexes derived from sodium thiosulfate.[2]

Other[edit]

Ammonium thiosulfate can be used as a fertilizer.[6] 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.[7]

Safety[edit]

LD50 (oral, rat) is 2890 mg/kg.[2]

See also[edit]

References[edit]

  1. ^ MSDS - Ammonium Thiosulfate
  2. ^ a b c J. J. Barbera, A. Metzger, M. Wolf (2012). "Sulfites, Thiosulfates, and Dithionites". Ullmann's Encyclopedia of Industrial Chemistry. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a25_477. ISBN 978-3527306732.
  3. ^ Praní černobílých filmů a papírů
  4. ^ Karlheinz Keller et al. "Photography" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a20_001
  5. ^ Aylmore, M.G; Muir, D.M (2001). "Thiosulfate leaching of gold—A review". Minerals Engineering. 14 (2): 135–174. doi:10.1016/S0892-6875(00)00172-2.
  6. ^ Minerální hnojiva se sírou
  7. ^ Ekologický monitor. Krátké zprávy ze zahraničních periodik – 19.1.2006