- Sodium dithionate
Name = Sodium dithionate
ImageFile = Sodium-dithionate-2D.png
ImageName = Sodium dithionate
IUPACName = Sodium dithionate
OtherNames = Sodium metabisulfate
Section1 = Chembox Identifiers
CASNo = 7631-94-9
Section2 = Chembox Properties
Formula = Na2S2O6
MolarMass = 174.11 g/mol
Appearance = Gray-white powder.
Density = ? g/cm3, solid.
Solubility = ? g/100 ml (?°C)
MeltingPt = 52°C (325.15 K) (decomp.)
BoilingPt = Decomposes.
Section3 = Chembox Structure
Section7 = Chembox Hazards
"For the sterilizing agent, see
sodium metabisulfite. For the reducing agent, see sodium dithionite."
Sodium dithionate Na2S2O6 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 NaHSO3 + MnO2 → Na2S2O6 + Mn(OH)2
3 Cl2 + Na2S2O3·5H2O + 6 NaOH → Na2S2O6 + 6 NaCl + 8 H2O
The dithionate ion represents
sulfurthat 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 energychange for the oxidation is about −300 kJ/mol.
It should not be confused with sodium dithionITE, Na2S2O4, 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 dioxidein sweet, moist foods such as those containing coconut-flavored interiors.
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