Sodium thiosulfate
IUPAC name	Sodium thiosulfate
Other names	Sodium hyposulfite Hyposulphite of soda
Identifiers
CAS number	7772-98-7
Properties
Molecular formula	Na2S2O3
Molar mass	158.09774 g/mol
Appearance	White crystals
Density	1.667 g/cm³, solid
Melting point	48.3 °C Image File history File links Download high-resolution version (1100x640, 129 KB) File links No pages on the English Wikipedia link to this file. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... For sodium in the diet, see Edible salt. ... This article is about the chemical element. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... For other uses, see Density (disambiguation). ... The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. ...
Boiling point	N/A Italic text This article is about the boiling point of liquids. ...
Solubility in water	Very Soluble
Basicity (pKb)	N/A
Structure
Coordination geometry	Tetrahedral anion
Hazards
MSDS	External MSDS
EU classification	Non-toxic.
NFPA 704	Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... The acid dissociation constant (Ka), also known as the acidity constant or the acid-ionization constant, is a specific equilibrium constant for the reaction of an acid with its conjugate base in aqueous solution [1]. // When an acid dissolves in water, it partly dissociates forming hydronium ions and its conjugate... The coordination geometry of an atom is the geometrical pattern formed by its neighbors in a molecule or a crystal. ... This page meets Wikipedias criteria for speedy deletion. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main European Union law concerning chemical safety. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links NFPA_704. ... 0 1 0
R-phrases	R35
S-phrases	(S1/2) S26 S37/39 S45
Flash point	Non flammable
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Sodium thiosulfate (Na₂S₂O₃) (sometimes spelled thiosulphate) is a colorless crystalline compound that is more familiar as the pentahydrate, Na₂S₂O₃•5H₂O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.” R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... For other uses, see Flash point (disambiguation). ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... For sodium in the diet, see Edible salt. ... This article is about the chemical element. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... For other uses, see Crystal (disambiguation). ... Pentahydrate is a hydrate that contains five molecules of water. ... For sodium in the diet, see Edible salt. ... This article is about the chemical element. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... This article is about the chemistry of hydrogen. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... In Chemistry Efflorescence is the formation of a powdery surface on crystals as a hydrate is converted to anhydrous form by losing loosely bound water of crystallization to the atmosphere. ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ...

The thiosulfate anion is tetrahedral in shape and is notionally derived by replacing one of the oxygen atoms by a sulfur atom in a sulfate anion. The S-S distance indicates a single bond, implying that the sulfur bears significant negative charge and the S-O interactions have more double bond character. The first protonation of thiosulfate occurs at sulfur. It has been suggested that thiosulfate ion be merged into this article or section. ... An anion is an ion with negative charge. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... This article is about the chemical element. ... The sulfate anion, SO42− The structure and bonding of the sulfate ion In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ...

Industrial production and laboratory synthesis

On an industrial scale, sodium thiosulfate is produced chiefly from liquid waste products of sodium sulfide or sulfur dye manufacture.^[1] Sodium sulfide, or Na2S, is a water soluble chemical compound. ... Look up dye in Wiktionary, the free dictionary. ...

Small scale synthesis is by boiling an aqueous solution of sodium sulfite with sulfur. In chemistry, sodium sulfite is a soluble compound of sodium. ... This article is about the chemical element. ...

As such, the anion S₂O₃²⁻ represents a water-soluble form of elemental sulfur.

Principal reactions and applications

Thiosulfate anion characteristically reacts with dilute acids to produce sulfur, sulfur dioxide and water:^[1] Note: this page refers to dilution in the sense of trademark law. ... For other uses, see Acid (disambiguation). ... This article is about the chemical element. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

S₂O₃²⁻(aq) + 2H⁺(aq) → S(s) + SO₂(g) + H₂O(l)

This reaction has been employed to generate colloidal sulfur. When the protonation is conducted at low temperatures, H₂S₂O₃ (thiosulfuric acid) can be obtained. It is a strong acid pK_a = 0.6, 1.7. Thiosulfuric acid is a sulfur oxoacid. ...

Iodometry

Perhaps most notably in the laboratory^{[citation needed]}, the thiosulfate anion reacts stoichiometrically with iodine, reducing it to iodide as it is oxidized to tetrathionate: In chemistry, stoichiometry is the study and calculation of quantitative (measurable) relationships of the reactants and products in chemical reactions (chemical equations). ... For other uses, see Iodine (disambiguation). ... An iodide ion is an iodine atom with a −1 (negative one) charge. ... The structure of the tetrathionate anion The tetrathionate anion, S4O62−, is a sulfur oxoanion derived from the compound tetrathionic acid, H2S4O6. ...

2 S₂O₃²⁻(aq) + I₂(aq) → S₄O₆²⁻(aq) + 2 I⁻(aq)

Due to the quantitative nature of this reaction, as well as the fact that Na₂S₂O₃•5H₂O has an excellent shelf-life, it is used as a titrant in iodometry. Na₂S₂O₃•5H₂O is also a component of iodine clock experiments. For other uses, see Iodine (disambiguation). ... Titration setup. ... Iodometry is a method of volumetric chemical analysis, a titration where the appearance or disappearance of elementary iodine indicates the end point. ...

This particular use can be set up to measure the oxygen content of water through a long series of reactions. It is also used in estimating volumetrically, the concentrations of certain compounds in solution (hydrogen peroxide, for instance), and in estimating the chlorine content in commercial bleaching powder and water. R-phrases , , , , S-phrases , , , ,, , , , Flash point Non-flammable Related Compounds Related compounds Water Ozone Hydrazine Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in...

Photographic processing

The terminal sulfur atom in S₂O₃²⁻ binds to soft metals with high affinity. Thus it dissolves silver halides, e.g. AgBr, which is a component of photographic emulsions: The HSAB concept, also known as HSAB theory, is widely used in chemistry for explaining stability of compounds, reaction paths etc. ... Look up affinity in Wiktionary, the free dictionary. ... This article is about the chemical element. ... Silver bromide (AgBr), a soft, pale-yellow, insoluble salt well known (along with other silver halides) for its unusual sensitivity to light. ...

2 S₂O₃²⁻ + AgBr → [Ag(S₂O₃)₂]³⁻) + Br^-

In this application to photographic processing, discovered by John Herschel and used for both film and paper processing, sodium thiosulfate is known as a photographic fixer. It has been suggested that this article or section be merged with photographic developer. ... John Herschel Sir John Frederick William Herschel (7 March 1792 – 11 May 1871) was an English mathematician and astronomer. ... This article is about motion pictures. ... Photographic fixer is a chemical used in the final step in the photographic processing of film or paper. ...

Gold extraction

Sodium thiosulfate is one component of an alternative lixiviant to cyanide for extraction of gold.^[2] It forms a strong complex with gold(I) ions, [Au(S₂O₃)₂]^3-. The advantage of this approach is that thiosulfate is essentially non-toxic and that ore types that are refractory to gold cyanidation (e.g. carbonaceous or Carlin type ores) can be leached by thiosulfate. Some problems with this alternative process include the high consumption of thiosulfate, and the lack of a suitable recovery technique, since [Au(S₂O₃)₂]^3- does not adsorb to activated carbon, which is the standard technique used in gold cyanidation to separate the gold complex from the ore slurry. Lixiviant is a liquid medium used in hydrometallurgy to selectively extract the desired metal from the ore or mineral. ... This article is about the chemical compound. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... The term refractory can refer to multiple things: A refractory clergyman is one who refused to swear an oath to the French Revolution-era French state under the Civil Constitution of the Clergy. ... Gold cyanidation (also known as the cyanide process or the MacArthur-Forrest Process) is a metallurgical technique for extracting gold from low-grade ore by converting the gold to water soluble aurocyanide metallic complex ions. ... This article belongs in one or more categories. ... In chemistry, adsorption of a substance is its concentration on a particular surface. ... Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... Gold cyanidation (also known as the cyanide process or the MacArthur-Forrest Process) is a metallurgical technique for extracting gold from low-grade ore by converting the gold to water soluble aurocyanide metallic complex ions. ...

Other uses

Sodium thiosulfate is also used:

• As a component in hand warmers and other chemical heating pads that produce heat by exothermic crystallization of a supercooled solution.
• In Bleach
• In pH testing of bleach substances. The universal indicator and any other liquid pH indicator are destroyed by bleach, rendering them useless for testing the pH. If one first adds sodium thiosulfate to such solutions, it will neutralize the color-removing effects of bleach and allow one to test the pH of bleach solutions with liquid indicators. The relevant reaction is akin to the iodine reaction: thiosulfate reduces the hypochlorite (active ingredient in bleach) and in so doing becomes oxidized to sulfate. The complete reaction is:

4 NaClO + Na₂S₂O₃ + 2 NaOH → 4 NaCl + 2 Na₂SO₄ + H₂O

• To dechlorinate tap water for aquariums or treat effluent from waste water treatments prior to release into rivers. The reduction reaction is analogous to the iodine reduction reaction. Treatment of tap water requires between 0.1 grams and 0.3 grams of pentahydrated (crystalline) sodium thiosulfate per 10 liters of water.
• To lower chlorine levels in swimming pools and spas following super chlorination.
• To remove iodine stains, e.g. after the explosion of nitrogen triiodide.
• As an antidote to cyanide poisoning. Thiosulfate acts as a sulfur donor for the conversion for cyanide to thiocyanate, catalyzed by the enzyme rhodanase.
• In bacteriological water assessment.
• In the tanning of leather.
• To demonstrate the concept of reaction rate in chemistry classes. The thiosulfate ion can decompose into the sulfite ion and a colloidal suspension of sulfur, which is opaque. The equation for this acid-catalysed reaction is as follows:
  S₂O₃²⁻(aq) → SO₃²⁻(aq) + S(s)
• To demonstrate the concept of supercooling in physics classes. Melted sodium thiosulfate is very easy to overcool to room temperature and when crystallization is forced, the sudden temperature jump to 48.3°C can be experienced by touch.
• As part of patina recipes for copper alloys.
• Often used in pharmaceutical preparations as an anionic surfactant to aid in dispersion.
• Treatment of calciphylaxis in hemodialysis patients with End-Stage Renal Disease

A pair of air-activated disposable hand warmers, US quarter to scale Crystallization-type hand warmer with scale showing metal disc trigger Hand warmers are small (sometimes disposable) packets which are held in the hand and produce heat on demand to warm cold hands. ... A heating pad is a pad used for warming of parts of the body in order to manage pain. ... Supercool redirects here. ... This article or section cites very few or no references or sources. ... For other uses, see PH (disambiguation). ... Nitrogen triiodide, also called nitrogen iodide, is the chemical compound with the formula NI3. ... This article is about the chemical compound. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... This article is about making hides into leather. ... Modern leather-working tools Leather is a material created through the tanning of hides and skins of animals, primarily cattlehide. ... Iron rusting - a chemical reaction with a slow reaction rate. ... It has been suggested that thiosulfate ion be merged into this article or section. ... Sulfites (also sulphite) are compounds that contain the sulfite ion SO32−. They are often used as preservatives in wines (to prevent spoilage and oxidation), dried fruits, and dried potato products. ... Supercool redirects here. ... The Statue of Liberty gets its green color from the patina formed on its copper surface Patinas are chemical compounds formed on the surface of metals. ... Copper has played a significant part in the history of mankind, which has used the easily accessible uncompounded metal for nearly 10,000 years. ...

References

1. ^ ^{a b} Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5
2. ^ Aylmore, M. G.; Muir, D. M. "Thiosulfate Leaching of Gold - a Review", Minerals Engineering, 2001, 14, 135-174