Potassium persulfate

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Potassium persulfate
Potassium persulfate.png
Ball-and-stick model of the crystal structure
Potassium persulfate as a white powder
Identifiers
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
Properties
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
Hazards
MSDS ICSC 1133
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.

Preparation[edit]

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.

Uses[edit]

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].

Precautions[edit]

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

References[edit]

  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)