Sodium dithionate

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Sodium dithionate
Sodium dithionate
General
Systematic name Sodium dithionate
Other names See text
Molecular formula Na2S2O6
Molar mass 174.11 g/mol
Appearance Gray-white powder.
CAS number [7631-94-9] [1]
Properties
Density and phase  ? g/cm3, solid.
Solubility in water  ? g/100 ml (?°C)
Melting point 52°C (325.15 K) (decomp.)
Boiling point Decomposes.
Structure
Molecular shape  ?
Coordination
geometry
 ?
Crystal structure  ?
Dipole moment  ? D
Hazards
MSDS External MSDS
Main hazards  ?
NFPA 704

3
2
2
 
Flash point Non-flammable
R/S statement R: R7, R22, R31.
S: S7/8, S26, S28, S43.
RTECS number JP2100000
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Other anions  ?
Other cations  ?
Related compounds  ?
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

For the sterilizing agent, see sodium metabisulfite

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 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 can be used as a reductant, react to reduce other species and be oxidized to sulfate. Sodium dithionate is sufficiently strong a reductant to reduce iron(III) oxide (rust) to iron(II), the more soluble form of iron. Iron(III) is common in soils and clays and gives clays a reddish hue.

When sodium dithionate acts as a reductant, it undergoes:

2 Na+ + 4 H2O + S2O42- → 2 SO42- + 8 H+ + 6 e- + 2 Na+

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