Potassium permanganate
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2008-07-11T20:01:07Z
Icairns
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{{Chembox new
| ImageFileL1 = Potassium-permanganate-unit-cell-3D-balls.png
| ImageSizeL1 = 150px
| ImageFileR1 = Potassium-permanganate-sample.jpg
| ImageSizeR1 = 150px
| IUPACName = Potassium manganate(VII)
| OtherNames = Potassium permanganate, Chameleon mineral, Condy's crystals
| Section1 = {{Chembox Identifiers
| CASNo = 7722-64-7
| PubChem = 24400
| SMILES = [[O-]] [Mn](=O)(=O)=O.[[K+]]
| KEGG = D02053
}}
| Section2 = {{Chembox Properties
| Formula = KMnO<sub>4</sub>
| MolarMass = 158.04 g/mol
| Appearance = purplish-bronze-gray needles;<br/>magenta–rose in solution
| Density = 2.703 g/cm³, solid
| MeltingPt = 270 °C ''decomp.''
| BoilingPt =
| Solubility = 6.38 g/100 ml at 20 °C
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[Orthorhombic]]
| Coordination =
| MolShape =
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = -813.4 kJ.mol<sup>-1</sup>
| DeltaHc =
| Entropy = 171.7 J.K<sup>-1</sup>.mol<sup>-1</sup>
| HeatCapacity = }}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://ptcl.chem.ox.ac.uk/MSDS/PO/potassium_permanganate.html External MSDS]
| MainHazards = Oxidant ('''O'''), Harmful ('''Xn'''), Dangerous for the environment ('''N''')
| RPhrases = {{R8}}, {{R22}}, {{R50/53}}
| SPhrases = {{S2}}, {{S60}}, {{S61}}
| NFPA-H =2
| NFPA-F =0
| NFPA-R =0
| NFPA-O = OX
| FlashPt =
| Autoignition =
}}
| Section8 = {{Chembox Related
| OtherAnions =
| OtherCations = [[Sodium permanganate]]
| OtherFunctn =
| Function = [[Permanganates]]
| OtherCpds = [[Potassium manganate]] (K<sub>2</sub>MnO<sub>4</sub>); [[Manganese heptoxide]];
[[Sodium permanganate]]
}}
}}
'''Potassium permanganate''' is the [[chemical compound]] [[potassium|K]][[manganese|Mn]][[oxygen|O]]<sub>4</sub>. In this salt, [[manganese]] is in the +7 [[oxidation state]]. The salt is also known as "permanganate of potash." The permanganate ion is a strong [[oxidizing agent]]. It dissolves in water to give deep purple solutions, evaporation of which gives prismatic purplish-black glistening crystals.<ref>F. Burriel, F. Lucena, S. Arribas and J. Hernández, (1985), ''Química Analítica Cualitativa'', page 688, ISBN 84-9732-140-5.</ref> In 2000, worldwide production was estimated at 30 000 t/a.<ref name=Ullmann>Arno H. Reidies "Manganese Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a16_123}}</ref>
It forms [[orthorhombic]] crystals with constants: ''a'' = 9.105, ''b'' = 5.720, ''c'' = 7.425 [[angstrom|Å]]. The Mn-O bond distances are 1.629 Å.
==Preparation==
Potassium permanganate is manufactured on a large scale from manganese dioxide ([[pyrolusite]], the mineral) is fused with [[potassium hydroxide]] and heated in air or with [[potassium nitrate]] (a source of oxygen). This process gives [[potassium manganate]], which upon electrolytic oxidation in alkaline solution gives potassium permanganate.
:MnO<sub>2</sub> + 2OH<sup><nowiki>−</nowiki></sup> + O<sub>2</sub> → MnO<sub>4</sub><sup>2<nowiki>−</nowiki></sup> + H<sub>2</sub>O
:MnO<sub>4</sub><sup>2<nowiki>−</nowiki></sup> + Cl<sub>2</sub> → MnO<sub>4</sub><sup><nowiki>−</nowiki></sup> + 2Cl<sup><nowiki>−</nowiki></sup>
Permanganates can also be generated by treating a solution of Mn<sup>2+</sup> ions with very strong oxidising agents like [[lead dioxide]], PbO<sub>2</sub>, or [[sodium bismuthate]], NaBiO<sub>3</sub>, and these reactions have been used to test for the presence of manganese due to the vivid violet colour of permanganate.
==Uses==
Almost all applications of potassium permanganate are derived from it being an [[oxidizing agent]].<ref name=Ullmann/> As a strong oxidant that does not generate toxic by products, KMnO<sub>4</sub> has many niche uses.
===Disinfectant and water treatment===
As an oxidant, potassium permanganate can act as a disinfectant. For example, dilute solutions are used as a treatment for [[Aphthous ulcer|canker sores]] (ulcers), disinfectant for the hands and treatment for mild [[pompholyx]], [[dermatitis]], and [[fungal]] infections of the hands or feet.{{Fact|date=September 2007}}
Potassium permanganate, obtainable at [[swimming pool|pool]] supply stores, is used in rural areas to remove [[iron]] and [[hydrogen sulfide]] (rotten egg smell) from [[water well|well]] and waste water.
====Biomedical uses====
Related to the use of KMnO<sub>4</sub> for water treatment, this salt is often employed as a specialized disinfectant for treating human and animal ailments. It has been used to induce [[abortions]], although with risks.<ref>{{cite journal | author = Obeng, B. B. | title = The lay use of potassium permanganate as an abortifacient | journal = [[Br J Clin Pract]] | year = 1968 | volume = 22 | issue = 11 | pages = 465–9 | pmid = 5696512}}</ref> In [[histology]] to bleach melanin which obscures tissue detail. Potassium permanganate can also be used to differentiate [[amyloid]] AA from other types of amyloid pathologically deposited in body tissues. Incubation of fixed tissue with potassium permanganate will prevent amyloid AA from staining with [[congo red]] whereas other types of amyloid are unaffected.<ref>{{cite journal | title = Potassium permanganate reaction in amyloidosis. A histologic method to assist in differentiating forms of this disease| author = Wright, J. R.; Calkins E.; Humphrey R. L. | journal = [[Lab Invest.]] | year = 1977 | volume = 36 | issue = 3 | pages = 274–81 | pmid = 839739}}</ref><ref>{{cite journal | title = The potassium permanganate method. A reliable method for differentiating amyloid AA from other forms of amyloid in routine laboratory practice | author = van Rijswijk, M. H.; van Heusden, C. W. | journal = [[Am J Pathol.]] | year = 1979 | volume = 97 | issue = 1 | pages = 43–58 | pmid = 495695}}</ref>
===Organic synthesis===
Aside from its use in water treatment, the other major applicaton of KMnO4 is as a reagent for the synthesis of organic compounds.<ref>{{cite journal | author = A. Fatiadi | title = The Classical Permanganate Ion: Still a Novel Oxidant in Organic Chemistry | year = 1987 | journal = [[Synthesis (journal)|Synthesis]] | volume = 1987 | issue = 2 | pages = 85–127 | doi = 10.1055/s-1987-27859 | format = review}}</ref> Significant amounts are required for the synthesis of [[ascorbic acid]], [[chloramphenicol]], [[saccharine]], [[isonicotinic acid]], and [[pyrazinoic acid]].<ref name=Ullmann/>
==Analytical chemistry==
Potassium permanganate can also be used to quantitatively determine the total oxidisable organic material in an aqueous sample. The value determined is known as the ''permanganate value.'' In [[analytical chemistry]], a standardized [[aqueous]] solution of KMnO<sub>4</sub> is sometimes used as an oxidizing [[titration|titrant]] for [[redox titration]]s. In a related way, it is used as a [[reagent]] to determine the [[Kappa number]] of wood pulp.
[[Image:KMnO4 in H2O.jpg|thumb|A solution of KMnO<sub>4</sub> in water, in a [[volumetric flask]]]]
Aqueous, acidic solutions of KMnO<sub>4</sub> are used to collect gaseous [[mercury (element)|mercury]] in flue gas during stationary source emissions testing.<ref>[[Code of Federal Regulations]](7-1-07) Edition,[[Title 40 of the United States Code|Title 40]], [[Part 60]], Appendix A-8, Method 29, Section 7.3.1</ref>
==Organic chemistry==
Dilute solutions of KMnO<sub>4</sub> convert [[alkene]]s into [[diol]]s (glycols). This behaviour is also used as a [[qualitative analysis|qualitative]] [[chemical test|test]] for the presence of double or triple bonds in a molecule, since the reaction decolorizes the permanganate solution; thus it is sometimes referred to as [[Baeyer's reagent]]. However, [[bromine]] serves better in measuring unsaturation (double or triple bonds) quantitatively, since KMnO<sub>4</sub>, being a very strong oxidizing agent, can react with impurities in a sample.
Under acidic conditions, the alkene double bond is cloven to give the appropriate [[carboxylic acid]]:<ref>{{OrgSynth | title = Carboxylic Acids from the Oxidation of Terminal Alkenes by Permanganate: Nonadecanoic Acid | author = Donald G. Lee, Shannon E. Lamb, and Victor S. Chang | collvol = 7 | collvolpages = 397 | year = 1990 | prep = cv7p0397}}</ref>
: CH<sub>3</sub>(CH<sub>2</sub>)<sub>17</sub>CH=CH<sub>2</sub> + [O] → CH<sub>3</sub>(CH<sub>2</sub>)<sub>17</sub>COOH
Potassium permanganate oxidizes aldehydes to carboxylic acids, such as the conversion of ''n''-[[heptanal]] to heptanoic acid:<ref>{{OrgSynth | author = John R. Ruhoff | title = ''n''-Heptanoic acid | collvol = 2 | collvolpages = 315 | prep = cv2p0315}}</ref>
: C<sub>6</sub>H<sub>13</sub>CHO + [O] → C<sub>6</sub>H<sub>13</sub>COOH
Even alkyl group (with a benzylic hydrogen) on an [[aromatic ring]] are oxidized, e.g. [[toluene]] to [[benzoic acid]].
Glycols are highly reactive toward KMnO<sub>4</sub>. And this vigorous reaction is used in survival kits as a fire starter. For example, a mixture of potassium permanganate and glycerol or pulverized glucose ignites readily. Its sterilizing properties are another reason for inclusion of KMnO<sub>4</sub> in a survival kit.<ref>{{cite web |url=http://www.primitiveways.com/chemical_fire.html |title=Chemical Fire |author = Bob Gillis and Dino Labiste}}</ref> In a related application, it is used for artistic purposes as an agent to prepare paper for fast bleaching. Lemon juice is enough to quickly remove colour from the paper and applied with a paint brush this can create interesting aesthetics.
==Acids and KMnO<sub>4</sub>==
Concentrated [[sulfuric acid]] reacts with KMnO<sub>4</sub> to give [[manganese(VII) oxide|Mn<sub>2</sub>O<sub>7</sub>]], which can be [[explosion|explosive]].<ref>F. A. Cotton, G. Wilkinson, C. A. Murillo, and M. Bochmann (April 1999). ''Advanced Inorganic Chemistry, 6th Edition''. Wiley-VCH. ISBN 0-471-19957-5</ref><ref>{{cite journal | author = Barthel, H. and Duvinage, B. | title = Clemens Winkler. His Experiments with Ozone in 1892 | journal = Praxis der Naturwissenschaften, Chemie | year = 2000 | volume = 49 | pages = 18ff}}</ref><ref>{{cite journal | author = Dzhabiev, T. S.; Denisov, N. N.; Moiseev, D. N. and Shilov, A. E. | title = Formation of Ozone During the Reduction of Potassium Permanganate in Sulfuric Acid Solutions | journal = [[Russian Journal of Physical Chemistry]] | year = 2005 | volume = 79 | pages = 1755–1760}}</ref> Similarly concentrated [[hydrochloric acid]] gives [[chlorine]]. The Mn-containing products from [[redox reaction]]s depend on the [[pH]]. [[Acidic]] solutions of permanganate are [[redox|reduced]] to the faintly pink [[manganese(II) sulfate]] ([Mn(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup>). In [[pH|neutral]] solution, permanganate is only reduced by 3e<sup>−</sup> to give MnO<sub>2</sub>, wherein Mn is in a +4 oxidation state. This is the material that stains one's skin when handling KMnO<sub>4</sub>. KMnO<sub>4</sub> spontaneously reduced in an [[alkaline]] solution to green [[potassium manganate|K<sub>2</sub>MnO<sub>4</sub>]], wherein manganese is in the +6 oxidation state. Potassium permanganate and sulfuric acid react to produce some [[ozone]], which has a high oxidising power and rapidly oxidises the alcohol, causing it to combust. As a similar reaction produces explosive Mn<sub>2</sub>O<sub>7</sub>, this should only be attempted with great care. An approximate equation for the ozone formation is shown below.
:6 KMnO<sub>4</sub>(aq) + 9 H<sub>2</sub>SO<sub>4</sub>(aq) → 6 MnSO<sub>4</sub>(aq) + 3 K<sub>2</sub>SO<sub>4</sub>(aq) + 9 H<sub>2</sub>O(l) + 5 O<sub>3</sub>(g)
==History==
In [[1659]] a German chemist, J.R. [[Johann Rudolf Glauber|Glauber]], fused a mixture of the mineral [[pyrolusite]] and [[potassium carbonate]] to obtain a material that, when dissolved in water, gave a green solution ([[potassium manganate]]) which slowly shifted to violet potassium permanganate and then finally red. This report represents the first description of the production of potassium permanganate.<ref>Weeks, M. E. and Leicester, H. M.; ''Discovery of the Elements'', Journal of Chemical Education '''1968'''</ref> Just under two hundred years later London chemist [[Henry Bollmann Condy]] had an interest in disinfectants, and marketed several products including ''ozonised water''. He found that fusing pyrolusite with [[sodium hydroxide|NaOH]] and dissolving it in water produced a solution with disinfectant properties. He patented this solution, and marketed it as ''Condy's Fluid''. Although effective, the solution was not very stable. This was overcome by using [[potassium hydroxide|KOH]] rather than [[sodium hydroxide|NaOH]]. This was more stable, and had the advantage of easy conversion to the equally effective potassium permanganate crystals. This crystalline material was known as ''Condy’s crystals'' or ''Condy’s powder''. Potassium permanganate was comparatively easy to manufacture so [[Henry Bollmann Condy|Condy]] was subsequently forced to spend considerable time in litigation in order to stop competitors from marketing products similar to ''Condy's Fluid'' or ''Condy's Crystals''.
Early photographers used it as a component of [[flash powder]]. It is now replaced with other oxidizers, due to the instability of permanganate mixtures. Aqueous solutions of KMnO<sub>4</sub> have been used together with [[T-Stoff]] (''i.e.'' 80% [[hydrogen peroxide]]) as propellant for the [[rocket]] plane [[Messerschmitt Me 163]]. In this application, it was known as [[Z-Stoff]]. This combination of propellants is sometimes still used in [[torpedo]]es.
==Safety==
Solid KMnO<sub>4</sub> is a strong oxidizer and in general it should be kept separated from oxidizable substances. Reaction with concentrated sulfuric acid produces the highly explosive manganese(VII) oxide (Mn<sub>2</sub>O<sub>7</sub>). As an oxidizer, potassium permanganate stains the hand and clothing as it is reduced to brown [[manganese(IV) oxide|MnO<sub>2</sub>]]. It is also used as antidote for some poisons, on which it acts by oxidizing them.
== References ==
{{reflist}}
== External links ==
*{{ICSC|0672|06}}
*[http://www.npi.gov.au/database/substance-info/profiles/52.html National Pollutant Inventory: Manganese and compounds Fact Sheet]
*[http://edis.ifas.ufl.edu/FA032 The use of potassium permanganate in fish ponds]
*[http://sciencehack.com/videos/view/1Kh5FpSWVMo Sugar, NaOH and KMnO4]
{{Antiseptics and disinfectants}}
{{Antidotes}}
[[Category:Potassium compounds]]
[[Category:Permanganates]]
[[Category:Oxidizing agents]]
[[Category:Disinfectants]]
[[Category:Firelighting]]
[[Category:DEA List II chemicals]]
[[Category:Pyrotechnic oxidizers]]
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