Ammonium thiosulfate
{{Chembox
| Watchedfields = changed
| verifiedrevid = 456691931
| ImageFile = AmmonS2O3.svg
| ImageFile1 = Ammonium-thiosulfate-3D-vdW.png
| ImageSizeL1 = 110px
| ImageSizeR1 = 130px
| IUPACName = Diammonium thiosulfate
| OtherNames = Ammonium thiosulphate, ATS
| Section1 = {{Chembox Identifiers
| CASNo = 7783-18-8
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = BKH1729645
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2H3N.H2O3S2/c;;1-5(2,3)4/h2*1H3;(H2,1,2,3,4)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = XYXNTHIYBIDHGM-UHFFFAOYSA-N
| PubChem = 6096946
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 4807475
| ChEBI = 147402
| SMILES = [O-]S([O-])(=O)=S.[NH4+].[NH4+]
| InChI = InChI=1S/2H3N.H2O3S2/c;;1-5(2,3)4/h2*1H3;(H2,1,2,3,4)
}}
| Section2 = {{Chembox Properties
| Formula = {{chem2|[NH4]2S2O3}}
| H=8|N=2|O=3|S=2
| Appearance = colorless or white, hygroscopic solid
| Density = 1.679 g/cm3
| MeltingPt = decomposes at 100 °C
| BoilingPt =
| Solubility = 173 g/100 mL (20 °C)
| SolubleOther = slightly soluble in acetone
insoluble in alcohol
}}
|Section3={{Chembox Structure
| Coordination =
| CrystalStruct = monoclinic
}}
| Section5 = {{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
| LD50 = 2980 mg/kg (rat, oral)
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Ammonium thiosulfate (ammonium thiosulphate in British English) is an inorganic compound with the formula {{chem2|[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.[http://www.sciencelab.com/msds.php?msdsId=9922934 MSDS - Ammonium Thiosulfate]
Production
It is produced by treating ammonium sulfite with sulfur at temperatures between 85 and 110 °C:{{Ullmann|author1=J. J. Barbera |author2=A. Metzger |author3=M. Wolf|year=2012|doi=10.1002/14356007.a25_477|isbn=978-3527306732|title=Sulfites, Thiosulfates, and Dithionites}}
:{{chem2|[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.{{Cite web |url=http://www.paladix.cz/clanek.php?aid=10304&sid=1&hledej= |title=Praní černobílých filmů a papírů |access-date=2011-07-30 |archive-date=2012-03-27 |archive-url=https://web.archive.org/web/20120327230245/http://www.paladix.cz/clanek.php?aid=10304&sid=1&hledej= |url-status=dead }} Fixation involves these chemical reactions (illustrated for silver bromide):{{Ullmann|first1=Karlheinz |last1=Keller|title=Photography|year=2005|doi= 10.1002/14356007.a20_001}}
:{{chem2|AgBr + 2 [NH4]2S2O3 → [NH4]3[Ag(S2O3)2] + [NH4]Br}}
:{{chem2|AgBr + 3 [NH4]2S2O3 → [NH4]5[Ag(S2O3)3] + [NH4]Br}}
Also exploiting the stability of thiosulfate coordination complexes, ammonium thiosulfate is also used for leaching of gold and silver. It works with presence of copper as a catalyst. This process is a nontoxic alternative gold cyanidation.{{cite journal| doi=10.1016/S0892-6875(00)00172-2 | volume=14 | issue=2 | title=Thiosulfate leaching of gold—A review | year=2001 | journal=Minerals Engineering | pages=135–174 | last1 = Aylmore | first1 = M.G | last2 = Muir | first2 = D.M| bibcode=2001MiEng..14..135A }} 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.
=Other=
Ammonium thiosulfate can be used as a fertilizer.{{cite journal|title=Evaluation of ammonium thiosulfate as a soil urease inhibitor|first1=G. W.|last1=McCarty|first2=J. M.|last2=Bremner1|first3=M. J.|last3=Krogmeier1|s2cid=28574791|journal=Fertilizer Research|pages=135–139|volume=24|issue=3|year=1990|doi=10.1007/BF01073581}} 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.{{cite journal|doi=10.3155/1047-3289.61.5.511|first=Grzegorz|last=Wielgosiński|s2cid=44546628|title=The Reduction of Dioxin Emissions from the Processes of Heat and Power Generation|journal= Journal of the Air & Waste Management Association|year=2011|pages=511–526|volume=61|issue=5|pmid=21608491|bibcode=2011JAWMA..61..511W }}
Safety
LD50 (oral, rat) is 2890 mg/kg.