Potassium persulfate is the inorganic compound with the formula K2S2O8. Also known as potassium peroxydisulfate or KPS, it is a white solid that is sparingly soluble in cold water, but dissolves better in warm water. This salt is a powerful oxidant, commonly used to initiate polymerizations.
3D model (JSmol)
|E number||E922 (glazing agents, ...)|
CompTox Dashboard (EPA)
|Molar mass||270.322 g/mol|
|Melting point||< 100 °C (212 °F; 373 K) (decomposes)|
|1.75 g/100 mL (0 °C) |
4.49 g/100 ml (20 °C)
|Solubility||insoluble in alcohol|
Refractive index (nD)
|Safety data sheet||ICSC 1133|
|GHS Signal word||Danger|
|H272, H302, H315, H317, H319, H334, H335, H371|
|P220, P261, P280, P305+351+338, P342+311|
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|802 mg/kg (oral, rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
- Not to be confused with potassium peroxymonosulfate.
- 2 KHSO4 → K2S2O8 + H2
It can also be prepared by adding potassium bisulfate (KHSO4) to a solution of the more soluble salt ammonium peroxydisulfate (NH4)2S2O8. In principle it can be prepared by chemical oxidation of potassium sulfate using fluorine.
This salt is used to initiate polymerization of various alkenes leading to commercially important polymers such as styrene-butadiene rubber and polytetrafluoroethylene and related materials. In solution, the dianion dissociates to give radicals:
- [O3SO-OSO3]2− ⇌ 2 [SO4]•−
As a strong yet stable bleaching agent it also finds use in various hair bleaches and lighteners. Such brief and non-continuous use is normally hazard free, however prolonged contact can cause skin irritation. It has been used as an improving agent for flour with the E number E922, although it is no longer approved for this use within the EU.
- Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry. 1 (2nd ed.). New York: Academic Press. p. 392. ISBN 978-0121266011.
- 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.pub2.
- Encyclopedia of Reagents for Organic Synthesis, vol. 1, pp. 193–197(1995)
- "Final Report on the Safety Assessment of Ammonium, Potassium, and Sodium Persulfate". International Journal of Toxicology. 20 (3): 7-21. January 2001. doi:10.1080/10915810152630710.