Potassium persulfate

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Potassium persulfate
Two potassium cations and one peroxydisulfate anion
Ball-and-stick model of the crystal structure
Potassium persulfate as a white powder
CAS number 7727-21-1 YesY
PubChem 24412
ChemSpider 22821 N
EC number 231-781-8
UN number 1492
RTECS number SE0400000
Jmol-3D images Image 1
Molecular formula K2S2O8
Molar mass 270.322 g/mol
Appearance white powder
Odor odorless
Density 2.477 g/cm3[1]
Melting point < 100 °C (212 °F; 373 K) (decomposes)
Solubility in water 1.75 g/100 mL (0 °C)
4.49 g/100 ml (20 °C)
Solubility insoluble in alcohol
Refractive index (nD) 1.467
EU Index 016-061-00-1
EU classification Oxidant (O)
Harmful (Xn)
Irritant (Xi)
R-phrases R8, R22, R36/37/38, R42/43
S-phrases (S2), S22, S24, S26, S37
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 802 mg/kg (oral, rat)[2]
Related compounds
Other anions Potassium sulfite
Potassium sulfate
Potassium peroxymonosulfate
Other cations Sodium persulfate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references
Not to be confused with potassium peroxymonosulfate.

Potassium persulfate is the inorganic compound with the formula K2S2O8. Also known as potassium peroxydisulfate or KPS, it is a white solid that is highly soluble in water. This salt is a powerful oxidant, commonly used to initiate polymerizations.


Potassium persulfate can be prepared by electrolysis of a cold solution potassium bisulfate in sulfuric acid at a high current density.[1]

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 polymerziation 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:[3]

[O3SO-OSO3]2- \overrightarrow{\leftarrow} 2 [SO4]

It is used in organic chemistry as an oxidizing agent,[4] for instance in the Elbs persulfate oxidation of phenols.

As a strong bleaching agent, it is used in hair dye substances as whitening agent with hydrogen peroxide.

It is a food additive[citation needed].


The salt is a strong oxidant and is incompatible with organic compounds.


  1. ^ a b F. Feher, "Potassium Peroxydisulfate" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 392.
  2. ^ http://chem.sis.nlm.nih.gov/chemidplus/rn/7727-21-1
  3. ^ Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort (2005), "Peroxo Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_177.pub2 
  4. ^ Encyclopedia of Reagents for Organic Synthesis, vol. 1, pp 193-197(1995)