Ammonium thiosulfate

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]

Ammonium thiosulfate
Names
IUPAC name
Diammonium thiosulfate
Other names
Ammonium thiosulphate, ATS
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.074
UNII
  • InChI=1S/2H3N.H2O3S2/c;;1-5(2,3)4/h2*1H3;(H2,1,2,3,4) checkY
    Key: XYXNTHIYBIDHGM-UHFFFAOYSA-N checkY
  • InChI=1S/2H3N.H2O3S2/c;;1-5(2,3)4/h2*1H3;(H2,1,2,3,4)
  • [O-]S([O-])(=O)=S.[NH4+].[NH4+]
Properties
[NH4]2S2O3
Molar mass 148.20 g·mol−1
Appearance colorless or white, hygroscopic solid
Density 1.679 g/cm3
Melting point decomposes at 100 °C
173 g/100 mL (20 °C)
Solubility slightly soluble in acetone
insoluble in alcohol
Structure
monoclinic
Hazards
Lethal dose or concentration (LD, LC):
2980 mg/kg (rat, oral)
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

Production

It is produced by treating ammonium sulfite with sulfur at temperatures between 85 and 110 °C:[2]

[NH4]2SO3 + S → [NH4]2S2O3

Applications

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

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

Ammonium thiosulfate can be used as a fertilizer.[6] As suggested by some research studies, it can also be used as an additive to coal-waste mixtures to reduce formation of dioxins and furans during combustion.[7]

Safety

LD50 (oral, rat) is 2890 mg/kg.[2]

See also

References
  1. MSDS - Ammonium Thiosulfate
  2. J. J. Barbera; A. Metzger; M. Wolf (2012). "Sulfites, Thiosulfates, and Dithionites". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a25_477.
  3. "Praní černobílých filmů a papírů". Archived from the original on 2012-03-27. Retrieved 2011-07-30.
  4. Keller, Karlheinz (2005). "Photography". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. 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. Bibcode:2001MiEng..14..135A. doi:10.1016/S0892-6875(00)00172-2.
  6. McCarty, G. W.; Bremner1, J. M.; Krogmeier1, M. J. (1990). "Evaluation of ammonium thiosulfate as a soil urease inhibitor". Fertilizer Research. 24 (3): 135–139. doi:10.1007/BF01073581. S2CID 28574791.
  7. Wielgosiński, Grzegorz (2011). "The Reduction of Dioxin Emissions from the Processes of Heat and Power Generation". Journal of the Air & Waste Management Association. 61 (5): 511–526. Bibcode:2011JAWMA..61..511W. doi:10.3155/1047-3289.61.5.511. PMID 21608491. S2CID 44546628.
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