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
Names
Other names
potassium peroxydisulfate
Anthion
potassium perdisulfate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.893
EC Number 231-781-8
E number E922 (glazing agents, ...)
RTECS number SE0400000
UN number 1492
Properties
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)
1.75 g/100 mL (0 °C)
4.49 g/100 ml (20 °C)
Solubility insoluble in alcohol
1.467
Structure
triclinic
Hazards
Safety data sheet ICSC 1133
GHS pictograms GHS03: Oxidizing GHS07: Harmful GHS08: Health hazard
GHS signal word DANGER
H272, H302, H315, H317, H319, H334, H335, H371
P220, P261, P280, P305+351+338, P342+311
NFPA 704
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
802 mg/kg (oral, rat)[2]
Related compounds
Other anions
Potassium sulfite
Potassium sulfate
Potassium peroxymonosulfate
Other cations
Sodium persulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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 sparingly soluble in cold water, but dissolves better in warm 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 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:[3]

[O3SO-OSO3]2− ⇌ 2 [SO4]•−

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

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.[5] 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.

Precautions[edit]

The salt is a strong oxidant and is incompatible with organic compounds. Prolonged skin contact can result in irritation.[5]

References[edit]

  1. ^ a b Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry. 1 (2nd ed.). New York: Academic Press. p. 392. ISBN 978-0121266011.
  2. ^ http://chem.sis.nlm.nih.gov/chemidplus/rn/7727-21-1
  3. ^ 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.
  4. ^ Encyclopedia of Reagents for Organic Synthesis, vol. 1, pp. 193–197(1995)
  5. ^ a b "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.