Potassium persulfate: Difference between revisions

{{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 = K₂S₂O₈

| MolarMass = 270.322 g/mol

| Appearance = white powder

| Odor = odorless

| Density = 2.477 g/cm³<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|K₂]][[Sulfate|S₂O₈]]. 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>

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>

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]]. 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>

:[O₃SO-OSO₃]²⁻ {{eqm}} 2 [SO₄]^•−

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.

The salt is a strong oxidant and is incompatible with organic compounds. Prolonged skin contact can result in irritation.<ref name=safety />

{{Persulfates}}