Peroxymonosulfuric acid

Chembox new
Name = Peroxymonosulfuric acid
ImageFile = Peroxymonosulfuric acid.svg
ImageFile1 = Caro's-acid-3D-balls.png ImageName1 = Ball-and-stick model of peroxymonosulfuric acid
OtherNames = persulfuric acid, peroxysulfuric acid,
peroxomonosulfuric acid;
Section1 = Chembox Identifiers
CASNo = 7722-86-3
RTECS =
Section2 = Chembox Properties
Formula = H₂SO₅
MolarMass = 114.04 g/mol
Appearance = white solid
Density = ??? g/cm³, solid
Solubility = soluble
MeltingPt = 45 °C
BoilingPt = decomposes
Section3 = Chembox Structure
Coordination = tetrahedral
CrystalStruct =
Dipole = ?
Section7 = Chembox Hazards
MainHazards = strong oxidizer

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.

History

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

ynthesis and production

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

::H₂O₂ + ClSO₂OH unicode|⇌ 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 unicode|⇌ 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.

Dangers

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 the compound, creating a highly unstable molecule such as Acetone Peroxide.

References

*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.