Sodium dithionate
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2008-07-03T17:55:33Z
GrNephrite
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{{Chembox new
| Name = Sodium dithionate
| ImageFile = Sodium-dithionate-2D.png
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| ImageName = Sodium dithionate
| IUPACName = Sodium dithionate
| OtherNames = Sodium metabisulfate
| Section1 = {{Chembox Identifiers
| CASNo = 7631-94-9
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| Section2 = {{Chembox Properties
| Formula = Na<sub>2</sub>S<sub>2</sub>O<sub>6</sub>
| MolarMass = 174.11 g/mol
| Appearance = Gray-white powder.
| Density = ? g/cm<sup>3</sup>, solid.
| Solubility = ? g/100 ml (?°C)
| MeltingPt = 52°C (325.15 K) (decomp.)
| BoilingPt = Decomposes.
}}
| Section3 = {{Chembox Structure
| MolShape =
| Coordination =
| CrystalStruct =
| Dipole =
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| Section7 = {{Chembox Hazards
| ExternalMSDS =
| MainHazards =
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''For the sterilizing agent, see [[sodium metabisulfite]]. For the reducing agent, see [[sodium dithionite]].''
'''Sodium dithionate''' Na<sub>2</sub>S<sub>2</sub>O<sub>6</sub> is an important compound for [[inorganic chemistry]]. It is also known under names '''disodium dithionate''', '''sodium hyposulfate''', and '''sodium metabisulfate'''.
Can be produced by following reactions:
2 NaHSO<sub>3</sub> + MnO<sub>2</sub> → Na<sub>2</sub>S<sub>2</sub>O<sub>6</sub> + Mn(OH)<sub>2</sub>
3 Cl<sub>2</sub> + Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub>·5H<sub>2</sub>O + 6 NaOH → Na<sub>2</sub>S<sub>2</sub>O<sub>6</sub> + 6 NaCl + 8 H<sub>2</sub>O
The dithionate ion represents [[sulfur]] that is oxidized relative to elemental sulfur, but not totally oxidized. Sulfur can be reduced to sulfide or totally oxidized to sulfate, with numerous intermediate oxidation states in inorganic moieties, as well as organosulfur compounds. Example inorganic ions include sulfite and thiosulfate.
Sodium dithionate is a very stable compound which is not oxidized by permanganate, dichromate or bromine. It can be oxidized to sulfate under strongly oxidizing conditions: these include boiling for one hour with 5 M sulfuric acid with an excess of potassium dichromate, or treating with an excess of hydrogen peroxide then boiling with concentrated hydrochloric acid. The [[Gibbs free energy]] change for the oxidation is about −300 kJ/mol.
It should not be confused with sodium dithionITE, Na<sub>2</sub>S<sub>2</sub>O<sub>4</sub>, which is a very different compound, and is a powerful reducing agent with many uses in chemistry and biochemistry. Confusion between dithionate and dithionite is commonly encountered, even in manufacturers' catalogues!
Sodium metabisulfate is also encountered occasionally as a food preservative, especially in combination with [[sulfur dioxide]] in sweet, moist foods such as those containing coconut-flavored interiors.
==References==
{{Unreferenced|date =September 2007}}
{{reflist}}
[[Category:Dithionates]]
[[Category:Sodium compounds]]
{{inorganic-compound-stub}}
[[ar:ثنائي ثيونات صوديوم]]