Thiosulfuric acid

Thiosulfuric acid
IUPAC name	sulfurothioic O-acid
Other names	thiosulfuric acid dihydroxidooxidosulfidosulfur
Identifiers
CAS number	[7772-98-7]
SMILES	OS(=O)(=S)O
Properties
Chemical formula	H2S2O3
Molar mass	114.14408
Solubility in water	decomposes
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Thiosulfuric acid is a sulfur oxoacid. The acid cannot be made by acidifying thiosulfate salts as the acid readily decomposes in water. The decomposition products can include sulfur, sulfur dioxide, hydrogen sulfide, polysulfanes, sulfuric acid and polythionates, depending on the exact reaction conditions. Anhydrous methods of producing the acid include:

(in diethyl ether at -78°C )

H₂S + SO₃ → H₂S₂O₃•nEt₂O

Na₂S₂O₃+2HCl → 2NaCl + H₂S₂O₃•2Et₂O

The anhydrous acid decomposes below 0°C:

H₂S₂O₃ → H₂S + SO₃

There is an isomeric form, a white crystalline adduct, H₂S.SO₃ which can be prepared at low temperature.

See also

• Sulfur oxoacids for other sulfur oxoacids

References

Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements, 2nd ed.; Butterworth-Heinemann: Oxford, 1997. ISBN 0-7506-3365-4