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Peroxydisulfuric acid is the inorganic compound with the chemical formula H2S2O8. Also called Marshall's acid after its inventor Prof Hugh Marshall,[1] it is a sulfur oxoacid.[2] In structural terms it can be written HO3SOOSO3H. It contains sulfur in its +6 oxidation state and a peroxide group. Its salts, commonly known as persulfates, are industrially important as powerful oxidizing agents.

Peroxydisulfuric acid
IUPAC names
peroxydisulfuric acid
Other names
Persulfuric acid, Peroxodisulfuric acid
3D model (JSmol)
Molar mass 194.13 g·mol−1
Appearance Colourless solid
Melting point 65 °C (149 °F; 338 K) (decomposes)
Conjugate base Peroxydisulfate
Related compounds
Other cations
Potassium persulfate
Sodium persulfate
Ammonium persulfate
Related compounds
Peroxymonosulfuric acid
Pyrosulfuric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

The acid is prepared by the reaction of chlorosulfuric acid with hydrogen peroxide:[3]

2ClSO3H + H2O2 → H2S2O8 + 2 HCl

Another method is the electrolysis of moderately concentrated sulfuric acid (60-70%) with platinum electrodes at high current density and voltage:

H2SO4 + H2O → H3O+ + HSO4 (dissociation of sulfuric acid)
2HSO4 → H2S2O8 + 2e (E0 = +2.4V) (bisulfate oxidation)
2H2SO4 → H2S2O8 + H2 (overall reaction)
3H2O → O3 + 6H+ (ozone produced as a side product)

See alsoEdit


  1. ^
  2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. ^ Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort, "Peroxo Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_177.pub2CS1 maint: Multiple names: authors list (link)