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The structure of the thiosulfate anion
A space-filling model of the thiosulfate anion
IUPAC names
  • sulfurothioate
  • trioxidosulfidosulfate(2−)
  • trioxido-1κ3O-disulfate(SS)(2−)[1]
3D model (JSmol)
  • InChI=1S/H2O3S2/c1-5(2,3)4/h(H2,1,2,3,4)/p-2
  • [O-]S(=O)(=S)[O-]
Molar mass 112.13 g·mol−1
Conjugate acid thiosulfuric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Thiosulfate (S2O2−3) (IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur. The prefix thio- indicates that the thiosulfate ion is a sulfate ion with one oxygen replaced by sulfur. Thiosulfate is a tetrahedral ion with C3v symmetry. It occurs naturally and is produced by certain biochemical processes. It rapidly dechlorinates water and is notable for its use to halt bleaching in the paper-making industry. Thiosulfate is mainly used in dying in textiles and the bleaching of natural substances.[2]

Sodium thiosulfate, commonly called hypo (from "hyposulfite"), was widely used in photography to fix black and white negatives and prints after the developing stage; modern 'rapid' fixers use ammonium thiosulfate as a fixing salt because it acts three to four times faster.[3] Some bacteria can metabolise thiosulfates.[4]


Thiosulfate is produced by the reaction of sulfite ion with elemental sulfur, and by incomplete oxidation of sulfides (pyrite oxidation), sodium thiosulfate can be formed by disproportionation of sulfur dissolving in sodium hydroxide (similar to phosphorus).


Tetrathionate anion is an oxidized derivative of thiosulfate.

Thiosulfates are stable only in neutral or alkaline solutions, but not in acidic solutions, due to disproportionation to sulfite and sulfur, the sulfite being dehydrated to sulfur dioxide:

This reaction may be used to generate an aqueous suspension of sulfur and demonstrate the Rayleigh scattering of light in physics. If white light is shone from below, blue light is seen from sideways and orange from above, due to the same mechanisms that color the sky at mid-day and dusk.[citation needed]

Thiosulfate reacts with iodine to give tetrathionate:

This reaction is key for iodometry. With bromine (X = Br) and chlorine (X = Cl), thiosulfate is oxidized to sulfate:

Reactions with metals and metal ions[edit]

Thiosulfate extensively forms diverse complexes with transition metals. In the era of silver-based photography, thiosulfate was consumed on a large scale as a "fixer" reagent. This application exploits thiosulfate's ability to dissolve silver halides. Thiosulfate is also used to extract or leach gold (sodium thiosulfate) and silver from their ores as a less toxic alternative to cyanide.[2]

Also reflecting its affinity for metals, thiosulfate rapid corrodes metals in acidic conditions. Steel and stainless steel are particularly sensitive to pitting corrosion induced by thiosulfate. Molybdenum improves the resistance of stainless steel toward pitting (AISI 316L hMo). In alkaline aqueous conditions and medium temperature (60 °C), carbon steel and stainless steel (AISI 304L, 316L) are not attacked, even at high concentration of base (30%w KOH), thiosulfate (10%w) and in presence of fluoride ion (5%w KF).[citation needed]


The very rare mineral sidpietersite, Pb4(S2O3)O2(OH)2,[5] as the presence of this anion in the mineral bazhenovite was recently disputed.[6]


Thiosulfate is an acceptable common name (but used almost always); functional replacement IUPAC name is sulfurothioate; the systematic additive IUPAC name is trioxidosulfidosulfate(2−) or trioxido-1κ3O-disulfate(SS)(2−).[1] The external sulfur has an oxidation state of –1 (−I) while the central sulfur atom has an oxidation number of +5 (+V).[7]

Latimer diagram for sulfur, one of which is thiosulfate (+2)


The enzyme rhodanase (thiosulfate sulfurtransferase) catalyzes the detoxification of cyanide by thiosulfate by transforming them into thiocyanate and sulfite:

Sodium thiosulfate has been considered as an empirical treatment for cyanide poisoning, along with hydroxocobalamin. It is most effective in a pre-hospital setting, since immediate administration by emergency personnel is necessary to reverse rapid intracellular hypoxia caused by the inhibition of cellular respiration, at complex IV.[8][9][10][11]

It activates thiosulfate sulfurtransferase (TST) in mitochondria. TST is associated with protection against obesity and type II (insulin resistant) diabetes.[12][13]


  1. ^ a b International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSCIUPAC. ISBN 0-85404-438-8. pp. 139,329. Electronic version.
  2. ^ a b Barbera, J. J.; Metzger, A.; Wolf, M. "Sulfites, Thiosulfates, and Dithionites". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a25_477.{{cite encyclopedia}}: CS1 maint: uses authors parameter (link)
  3. ^ Sowerby, A. L. M., ed. (1961). Dictionary of Photography: A Reference Book for Amateur and Professional Photographers (19th ed.). London: Illife Books Ltd.[page needed]
  4. ^ C.Michael Hogan. 2011. Sulfur. Encyclopedia of Earth, eds. A.Jorgensen and C.J.Cleveland, National Council for Science and the environment, Washington DC
  5. ^, Mineral Handbook[full citation needed]
  6. ^[full citation needed]
  7. ^ Descriptive Inorganic Chemistry 6.ed. p.462 ISBN 978-1-319-15411-0
  8. ^ Hall, Alan H.; Dart, Richard; Bogdan, Gregory (2007). "Sodium Thiosulfate or Hydroxocobalamin for the Empiric Treatment of Cyanide Poisoning?". Annals of Emergency Medicine. 49 (6): 806–13. doi:10.1016/j.annemergmed.2006.09.021. PMID 17098327.
  9. ^ Hamel, J. (2011). "A Review of Acute Cyanide Poisoning with a Treatment Update" (PDF). Critical Care Nurse. 31 (1): 72–81, quiz 82. doi:10.4037/ccn2011799. PMID 21285466.
  10. ^ Shepherd, G.; Vélez, L. I (2008). "Role of Hydroxocobalamin in Acute Cyanide Poisoning". Annals of Pharmacotherapy. 42 (5): 661–9. doi:10.1345/aph.1K559. PMID 18397973. S2CID 24097516.
  11. ^ Miles, Bryant (February 24, 2003). "Inhibitors & Uncouplers" (PDF). Texas A&M University. Retrieved 25 November 2015.
  12. ^ Stylianou, I. M.; et al. (2005). "Microarray gene expression analysis of the Fob3b obesity QTL identifies positional candidate gene Sqle and perturbed cholesterol and glycolysis pathways". Physiological Genomics. 20 (3): 224–232. CiteSeerX doi:10.1152/physiolgenomics.00183.2004. PMID 15598878.
  13. ^ Morton, N. M.; Beltram, J.; Carter, R. N.; et al. (2016). "Genetic identification of thiosulfate sulfurtransferase as an adipocyte-expressed antidiabetic target in mice selected for leanness". Nature Medicine. 22 (7): 771–779. doi:10.1038/nm.4115. PMC 5524189. PMID 27270587.

External links[edit]