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Peroxymonosulfuric acid

Peroxymonosulfuric acid

Systematic name Peroxysulfuric acid
Other names persulfuric acid, peroxysulfuric acid,
peroxomonosulfuric acid;
Molecular formula H2SO5
Molar mass 114.04 g/mol
Appearance white solid
CAS number 7722-86-3
Density and phase  ??? g/cm3, solid
Solubility in water soluble
in methanol soluble
Melting point 45 °C
Boiling point decomposes
Coordination geometry tetrahedral
Crystal structure  ?
Dipole moment  ?
MSDS External MSDS
Main hazards strong oxidizer
NFPA 704
Flash point n/a
R/S statement  ?
RTECS number  ?
Supplementary data page
Structure & properties n, εr, etc.
Thermodynamic data Phase behaviour
Solid, liquid
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Peroxymonosulfuric acid, also known as persulfuric acid, peroxysulfuric acid, or as Caro's acid, is H2SO5, a colorless solid melting at 45 °C. In this acid, the S(VI) center adopts its characteristic tetrahedral geometry; the connectivity is indicated by the formula HO-O-S(O)2-OH.

H2SO5 is sometimes confused with H2S2O8, known as peroxydisulfuric acid. The disulfuric acid, which appears to be more widely used as its alkali metal salts, has the structure HO-S(O)2-O-O-S(O)2-OH.



H2SO5 was first described by Heinrich Caro, for whom it is named.

Synthesis and production

The laboratory scale preparation of Caro's acid involve the combination of chlorosulfuric acid and hydrogen peroxide.

H2O2 + ClSO2OH H2SO5 + HCl

Large scale production of Caro's acid is usually done on site, due to its instability. According to the patent by Martin, Caro's acid is produced by reacting >85% sulfuric acid and >50% hydrogen peroxide ("Piranha solution").

H2O2 + H2SO4 H2SO5 + H2O

Uses in industry

H2SO5 has been used for a variety of disinfectant and cleaning applications, e.g., swimming pool treatment and denture cleaning. Alkali metal salts of H2SO5 show promise for the delignification of wood.

Ammonium, sodium, and potassium salts of H2SO5 are used in the plastics industry as polymerization initiators, etchants, desizing agents, soil conditioner, and for decolorizing and deodorizing oils.

Potassium peroxymonosulfate, KHSO5, is the potassium acid salt of peroxymonosulfuric acid. It is widely used as an oxidizing agent.


As with all strong oxidizing agents, peroxysulfuric acid should be kept away from organic compounds such as ethers and acetones because of its ability to peroxidize the compound, creating a highly unstable molecule such as Acetone Peroxide.


  • Martin, P. L. (USA). U.S. Pat. Appl. Publ. (2005), 21 pp. CODEN: USXXCO US 2005031530 A1 20050210 Patent written in English. Application: US 2004-878176 20040628. Priority: US 2003-494009 20030807. CAN 142:179838 AN 2005:122569 CAPLUS
  • "Treatment of Softwood Kraft Pulps with Peroxymonosulfate Before Oxygen Delignification. Springer, E. L.; McSweeny, J. D. Tappi Journal (1993), 76, 194-9.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Peroxymonosulfuric_acid". A list of authors is available in Wikipedia.
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