Peroxymonosulfuric acid, (H2SO5), also known as persulfuric acid, peroxysulfuric acid, or Caro's acid, has a melting point of 45 degree Celsius. 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. It is one of the strongest oxidants known (E0 = +2.51 V) and is highly explosive.
|Systematic IUPAC name|
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||114.078 g mol−1|
|Density||2.239 g cm−3|
|Tetrahedral at S|
|Main hazards||strong oxidizer|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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.
Synthesis and productionEdit
- H2O2 + ClSO2OH ⇌ H2SO5 + HCl 
Published patents include more than one reaction for preparation of Caro's acid, usually as an intermediate for the production of potassium monopersulfate (PMPS), a bleaching and oxidizing agent. One patent for production of Caro's acid for this purpose gives the following reaction:
- H2O2 + H2SO4 ⇌ H2SO5 + H2O 
Uses in industryEdit
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.
Pure Caro's acid is highly explosive. Explosions have been reported at Brown University and Sun Oil. As with all strong oxidizing agents, peroxysulfuric acid should be kept away from organic compounds such as ethers and ketones because of its ability to peroxidize these compounds, creating highly unstable molecules such as acetone peroxide.
- International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 139. Electronic version.
- "peroxysulfuric acid (CHEBI:29286)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute. 20 November 2007. Retrieved 17 November 2011.
- Caro, H. (1898). "Zur Kenntniss der Oxydation aromatischer Amine" [[Contribution] to [our] knowledge of the oxidation of aromatic amines]. Zeitschrift für angewandte Chemie. 11 (36): 845–846. doi:10.1002/ange.18980113602.
- "Synthesis of Caro's acid". PrepChem.com. 2017-02-13. Retrieved 2018-10-12.
- A method and apparatus for producing a peroxyacid solution, retrieved 2018-10-12
- Springer, E. L.; McSweeny, J. D. (1993). "Treatment of softwood kraft pulps with peroxymonosulfate before oxygen delignification". Tappi Journal. 76 (8): 194–199. ISSN 0734-1415.
- J.O. Edwards (1955). "SAFETY". Chem. Eng. News. 33 (32): 3336. doi:10.1021/cen-v033n032.p3336.