View source for Potassium persulfate

{{distinguish|Potassium peroxymonosulfate}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 441025344
| Name = Potassium persulfate
| ImageFile = Potassium persulfate.svg
| ImageName = Two potassium cations and one peroxydisulfate anion
| ImageFile1 = Potassium-persulfate-xtal-1997-3D-balls.png
| ImageName1 = Ball-and-stick model of the crystal structure
| ImageFile2 = Peroxodisíran draselný.JPG
| ImageName2 = Potassium persulfate as a white powder
| OtherNames = {{Unbulleted list|potassium peroxydisulfate|Anthion|potassium perdisulfate}}
|Section1={{Chembox Identifiers
| CASNo = 7727-21-1
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 6B86K0MCZC
| PubChem = 24412
| EINECS = 231-781-8
| UNNumber = 1492
| RTECS = SE0400000
| SMILES = [O-]S(=O)(=O)OOS(=O)(=O)[O-].[K+].[K+] 
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 22821
| InChI = 1/2K.H2O8S2/c;;1-9(2,3)7-8-10(4,5)6/h;;(H,1,2,3)(H,4,5,6)/q2*+1;/p-2
| InChIKey = USHAGKDGDHPEEY-NUQVWONBAA
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/2K.H2O8S2/c;;1-9(2,3)7-8-10(4,5)6/h;;(H,1,2,3)(H,4,5,6)/q2*+1;/p-2
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = USHAGKDGDHPEEY-UHFFFAOYSA-L
 }}
|Section2={{Chembox Properties
| Formula = K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>
| MolarMass = 270.322 g/mol
| Appearance = white powder
| Odor = odorless
| Density = 2.477 g/cm<sup>3</sup><ref name="Georg" />
| Solubility = 1.75 g/100 mL (0&nbsp;°C) <br> 4.49 g/100 mL (20&nbsp;°C)
| SolubleOther = insoluble in [[ethanol|alcohol]]
| MeltingPt= <
| MeltingPtC = 100
| MeltingPt_notes = (decomposes)
| RefractIndex = 1.467
 }}
|Section3={{Chembox Structure
| CrystalStruct = triclinic
 }}
|Section7={{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1133.htm ICSC 1133]
| GHSPictograms = {{GHS03}} {{GHS07}} {{GHS08}}
| GHSSignalWord = '''DANGER'''
| HPhrases = {{H-phrases|272|302|315|317|319|334|335|371}}
| PPhrases = {{P-phrases|220|261|280|305+351+338|342+311}}
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 1
| NFPA-S = OX
| FlashPt = Non-flammable
| PEL = 
| LD50 = 802 mg/kg (oral, rat)<ref>{{Cite web|url=https://chem.nlm.nih.gov/chemidplus/rn/7727-21-1|title=ChemIDplus - 7727-21-1 - USHAGKDGDHPEEY-UHFFFAOYSA-L - Potassium persulfate|first=Michael|last=Chambers|website=chem.nlm.nih.gov}}</ref>
 }}
|Section8={{Chembox Related
| OtherAnions = [[Potassium sulfite]]<br/>[[Potassium sulfate]]<br/>[[Potassium peroxymonosulfate]]
| OtherCations = [[Sodium persulfate]]<br/>[[Ammonium persulfate]]
| OtherFunction = 
| OtherFunction_label = 
| OtherCompounds = 
 }}
}}
'''Potassium persulfate''' is the [[inorganic compound]] with the formula [[Potassium|K<sub>2</sub>]][[Sulfate|S<sub>2</sub>O<sub>8</sub>]]. Also known as '''potassium peroxydisulfate''', 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 [[polymerization]]s.

==Structure==
The sodium and potassium salts are very similar.  In the potassium salt, the O-O distance is 1.495{{nbsp}}Å.  The individual sulfate groups are tetrahedral, with three short S-O distances near 1.43 and one long S-O bond at 1.65{{nbsp}}Å.<ref>{{cite journal |journal=Zhurnal Strukturnoi Khimii|year=1997|volume=38|page=922-929|last1=Naumov |first=D.Yu. |last2=Virovets |first2=A.V. |last3=Podberezskaya |first3=N.V. |last4=Novikov |first4=P.B. |last5=Politov |first5=A.A. |title=Redetermination of the Crystal Structure of Potassium Peroxodisulfate (K2S2O8)}}</ref>

==Preparation==
Potassium persulfate can be prepared by [[electrolysis]] of a cold solution [[potassium bisulfate]] in [[sulfuric acid]] at a high current density.<ref name="Georg">{{cite book|last=Brauer|first=Georg|title=Handbook of Preparative Inorganic Chemistry |volume=1 |edition=2nd |year=1963 |publisher=Academic Press |location=New York |isbn=978-0121266011 |page=392 |url=https://books.google.com/books?id=TLYatwAACAAJ&q=Handbook+of+Preparative+Inorganic+Chemistry}}</ref><ref>{{cite book|last1=Girolami |first1=G. S.|last2= Rauchfuss|first2= T. B. |last3=Angelici|first3= R. J.|title= Synthesis and Technique in Inorganic Chemistry|publisher= University Science Books|location= Mill Valley, CA|date= 1999|ISBN=0935702482}}</ref>
: 2 KHSO<sub>4</sub> → K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> + H<sub>2</sub>

It can also be prepared by adding potassium bisulfate (KHSO<sub>4</sub>) to a solution of the more soluble salt [[ammonium peroxydisulfate]] (NH<sub>4</sub>)<sub>2</sub>S<sub>2</sub>O<sub>8</sub>. In principle it can be prepared by chemical oxidation of [[potassium sulfate]] using [[fluorine]].  Several million kilograms of the ammonium, sodium, and potassium salts of peroxydisulfate are produced annually.

==Uses==
This salt is used to [[Radical initiator|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:<ref name = Ullmann>{{Ullmann | title = Peroxo Compounds, Inorganic |author=Harald Jakob |author2=Stefan Leininger |author3=Thomas Lehmann |author4=Sylvia Jacobi |author5=Sven Gutewort | doi = 10.1002/14356007.a19_177.pub2}}</ref>
:[O<sub>3</sub>SO-OSO<sub>3</sub>]<sup>2−</sup>   {{eqm}}   2 [SO<sub>4</sub>]<sup>•−</sup>

It is used in [[organic chemistry]] as an [[oxidizing agent]],<ref>''Encyclopedia of Reagents for Organic Synthesis'', vol. 1, pp. 193–197(1995)</ref> for instance in the [[Elbs persulfate oxidation]] of [[phenol]]s and the [[Boyland–Sims oxidation]] of [[aniline]]s.

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.<ref name=safety>{{cite journal|title=Final Report on the Safety Assessment of Ammonium, Potassium, and Sodium Persulfate|journal=International Journal of Toxicology|date=January 2001|volume=20|issue=3|doi=10.1080/10915810152630710|pmid=11766134 | last1 = Pang | first1 = S | last2 = Fiume | first2 = MZ|pages=7–21|s2cid=25763799}}</ref>
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==
The salt is a strong oxidant and is incompatible with organic compounds. Prolonged skin contact can result in irritation.<ref name=safety />

==References==
{{reflist}}

{{Potassium compounds}}
{{Persulfates}}
{{E number infobox 920-929}}

[[Category:Persulfates]]
[[Category:Potassium compounds]]
[[Category:Oxidizing agents]]
[[Category:Radical initiators]]