Potassium permanganate
Template:Cs1 config Template:Infobox drug Template:Chembox Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, which dissolves in water as K+ and [[permanganate|Template:Chem]] ions to give an intensely pink to purple solution.
Potassium permanganate is widely used in the chemical industry and laboratories as a strong oxidizing agent, and also traditionally as a medication for dermatitis, for cleaning wounds, and general disinfection. It is on the World Health Organization's List of Essential Medicines.<ref name="WHO21st">Template:Cite book</ref> It has a great variety of niche uses such as biocide for water treatment purposesTemplate:Cn and for tanning and dyeing cloth.<ref name="k821"/> In 2000, worldwide production was estimated at 30,000 tons.Template:Cn
It is also referred to as chameleon mineral, Condy's crystals, permanganate of potash, hypermangan, purple potion powder, permanganic acid (potassium salt),<ref name="k821"/> and purple salt.<ref name="k821"/>
Properties
Potassium permanganate is the potassium salt of the tetrahedral transition metal oxo complex permanganate, in which four Template:Chem2 ligands are bound to a manganese(VII) center.Template:Citation needed Potassium permanganate is odorless and slightly sweet and astringent in taste.<ref name="k821">Template:Cite book</ref> It is soluble in water, sulfuric acid, acetic anhydride, and benzonitrile, but dissolves best in methanol and acetone.<ref name="k821"/>
Structure
Template:Chem2 forms orthorhombic crystals with constants: a = 910.5 pm, b = 572.0 pm, c = 742.5 pm. The overall motif is similar to that for barium sulfate, with which it forms solid solutions.<ref>Template:Cite book</ref> In the solid (as in solution), each Template:Chem2 centre is tetrahedral. The Mn–O distances are 1.62 Å.<ref>Template:Cite journal</ref>
Color
The purplish-black color of solid potassium permanganate, and the intensely pink to purple color of its solutions, is caused by its permanganate anion, which gets its color from a strong charge-transfer absorption band caused by excitation of electrons from oxo ligand orbitals to empty orbitals of the manganese(VII) center.<ref>Template:Cite book</ref> The crystal form can range from purple to black or gray, and has a blue metallic sheen.<ref name="k821"/>
Medical uses
Mechanism of action
Potassium permanganate functions as a strong<ref name="k821"/> oxidizing agent. Through this mechanism it results in disinfection, astringency, and reduced odors.<ref name="Derm2017">Template:Cite web</ref><ref name="WHO Prescribing">Template:Cite book</ref><ref name="k821"/>
Clinical use
Potassium permanganate is no longer the preferred treatment for dermatological conditions<ref name="Derm2017"/> and no form of it is labeled for human use by the US Food and Drug Administration.<ref name="Yanong"/> It should never be taken internally, because it is highly toxic and corrosive to mucous membranes and skin.<ref name="Maronn"/><ref name="FDA20172"/><ref name="Derm2017"/><ref name="Olson"/><ref name="k821"/>
Traditionally potassium permanganate was prescribed for a number of skin conditions, including fungal infections of the foot, impetigo, pemphigus, superficial wounds, dermatitis, and topical ulcers.<ref name="BNF69">Template:Cite book</ref><ref name="WHO2008">Template:Cite book Also accessible via WHO Publications.</ref><ref name="k821"/> Radioactive contamination of the skin could be cleaned with potassium permanganate<ref name="k821"/> and vigorous scrubbing. For topical ulcers it was used together with procaine benzylpenicillin.<ref name="WHO2008" /> Typically it was used in skin conditions that produce a lot of liquid.<ref name="BNF69" /> It could be applied as a soaked dressing or a bath.<ref name="WHO2008"/> Petroleum jelly may be used on the nails before soaking to prevent their discoloration.<ref name="Ox2011">Template:Cite book</ref> For treating eczema, it was recommended using for only a few days at a time due to irritating the skin.<ref name="Nurse20033">Template:Cite web</ref>
The US Food and Drug Administration does not recommend its use in the crystal or tablet form. It should only be used in a diluted liquid form.Template:Cn
Historical use
Potassium permanganate was first made in the 1600s and came into common medical use at least as early as the 1800s.<ref name="Stout_2013">Template:Cite book</ref> During World War I Canadian soldiers were given potassium permanganate (to be applied mixed with an ointment) in an effort to prevent sexually transmitted infections.<ref>Template:Cite book</ref> Some have attempted to bring about an abortion by putting it in the vagina, though this is not effective.<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref name="FDA20172">Template:Cite web</ref> Other historical uses have included an effort to wash out the stomach in those with strychnine or picrotoxin poisoning.<ref>Template:Cite web</ref>
Side effects
Side effects from topical use include irritation of the skin and discoloration of clothing.<ref name="WHO2008"/> A harsh burn on a child from an undissolved tablet has been reported.<ref name="Nurse20033"/> Higher concentration solutions can result in chemical burns.<ref name="Olson">Template:Cite book</ref> Therefore, in 2015 the British National Formulary recommended 100 mg be dissolved in a liter of water before use to form a 1:10,000 (0.01%) solution.<ref name="Nurse20033"/><ref name="BNF692">Template:Cite book</ref><ref name="WHO2008"/> Wrapping the dressings soaked with potassium permanganate is not recommended.Template:Citation needed
Toxicology
Potassium permanganate is toxic if taken by mouth.<ref name="Maronn">Template:Cite book</ref><ref name="k821"/> Concentrated solutions when drunk have resulted in acute respiratory distress syndrome or swelling of the airway.<ref name="Schonwald_2004">Template:Cite book</ref> Effects may include nausea, vomiting, and shortness of breath.<ref name="Patnaik_2007">Template:Cite book</ref> If a sufficiently large amount (about 10 grams) is eaten death may occur.<ref name="Patnaik_2007" /> Concentrated solutions of potassium permanganate and repeated exposure cause skin corrosion and dermatitis.<ref name="k821"/>
Recommended measures for those who have ingested potassium permanganate include gastroscopy.<ref name="Schonwald_2004" /> Activated charcoal or medications to cause vomiting are not recommended. While medications like ranitidine and acetylcysteine may be used in toxicity, evidence for this use is poor.<ref name="Schonwald_2004" />
Pharmaceuticals
In the United States the FDA requires tablets of the medication to be sold by prescription.<ref name="FDA20172"/> Potassium permanganate, however, does not have FDA approved uses<ref name="Yanong">Template:Cite web</ref> and therefore non medical grade potassium permanganate is sometimes used for medical purposes.Template:Citation needed
It is available under a number of brand names including Permasol, Koi Med Tricho-Ex, and Kalii permanganas RFF.<ref>Template:Cite web</ref> It is occasionally called "Condy's crystals".<ref name="Derm20172">Template:Cite web</ref>
Veterinary medicine
Potassium permanganate may be used to prevent the spread of glanders among horses.<ref>Template:Cite book</ref>
Industrial and other uses
Almost all applications of potassium permanganate exploit its oxidizing properties.<ref name="Ullmann" /> As a strong oxidant that does not generate toxic byproducts, KMnO4 has many niche uses.Template:Citation needed
Water treatment
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Potassium permanganate is used extensively in the water treatment industry.Template:Sfn It is used to remove ironTemplate:Sfn and hydrogen sulfide (rotten egg smell) from well water via a "manganese greensand" filter.Template:Cn "Pot-Perm" is also obtainable at pool supply stores and is used additionally to treat wastewater.Template:Cn Historically it was used to disinfect drinking water,<ref>Template:Cite book</ref><ref name="Northern Advocate">Template:Cite web</ref> though the EPA considers it a poor disinfectant.Template:Sfn It can turn water a fuchsia or pink color.<ref>Template:Cite news</ref><ref name="Northern Advocate"/>Template:Sfn Modern hiking and survivalist guides advise against using potassium permanganate in the field because it is difficult to dose correctly.<ref name="Vogel">Template:Cite book</ref>
Fisheries and aquatic management
Potassium permanganate is not FDA approved for use with food fish in the United States, however it is categorized under "regulatory action deferred" and is legal to use because the FDA considers it "low regulatory priority" and at low risk for adverse human health effects.<ref name="Yanong"/><ref>Template:Cite web</ref><ref>Template:Harvnb: "At the time of this writing, FDA has also given copper sulfate (CuSO 4) and potassium permanganate (KMnO4) deferred status, which means that these treatments may be used without legal prosecution, but they may lose deferred status if evidence is found of any danger to the human consumer."</ref>
Potassium permanganate is a treatment for Ichthyophthirius multifiliis (commonly known as "ich") and protozoa (such as Trichodina), which infect and usually kill freshwater aquarium fish.<ref>Template:Cite book</ref> A minimum dose of 2 ppm is required. Water with more organic load and a higher number of organisms including algae requires more permanganate. High concentrations and use more than once per week kill fish. Food fish require a 7-day period after treatment before they can be consumed.<ref>Template:Harvnb</ref><ref name="Yanong"/>
An alternative application is in the control of nuisance organisms such as zebra musselsTemplate:Sfn in freshwater collection and treatment systems.Template:Cn
Rotenone can be deactivated in water with the use of potassium permanganate to lower toxicity to acceptable levels. A 1:1 ratio of permanganate to rotenone is insufficient to deactivate rotenone in most situations.<ref>Template:Harvnb</ref>
Synthesis of organic compounds
A major application of KMnO4 is as a reagent for the synthesis of organic compounds.<ref>Template:Cite journal</ref> Significant amounts are required for the synthesis of ascorbic acid, chloramphenicol, saccharin, isonicotinic acid, and pyrazinoic acid.<ref name="Ullmann" />
KMnO4 is used in qualitative organic analysis to test for the presence of unsaturation. It is sometimes referred to as Baeyer's reagent after the German organic chemist Adolf von Baeyer. The reagent is an alkaline solution of potassium permanganate. Reaction with double or triple bonds (Template:Chem2 or Template:Chem2) causes the color to fade from purplish-pink to brown. Aldehydes and formic acid (and formates) also give a positive test.<ref>Template:Cite web</ref> The test is antiquated.
KMnO4 solution is a common thin layer chromatography (TLC) stain for the detection of oxidizable functional groups, such as alcohols, aldehydes, alkenes, and ketones. Such compounds result in a white to orange spot on TLC plates.<ref>Template:Cite web</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref>
Analytical use
Potassium permanganate can be used to quantitatively determine the total oxidizable organic material in an aqueous sample. The value determined is known as the permanganate value. In analytical chemistry, a standardized aqueous solution of KMnO4 is sometimes used as an oxidizing titrant for redox titrations (permanganometry). As potassium permanganate is titrated, the solution becomes a light shade of purple, which darkens as excess of the titrant is added to the solution. In a related way, it is used as a reagent to determine the Kappa number of wood pulp. For the standardization of KMnO4 solutions, reduction by oxalic acid is often used.<ref>Template:Cite journal</ref> In agricultural chemistry, it is used for estimation of active carbon in soil.<ref>Template:Cite web</ref>
Aqueous, acidic solutions of KMnO4 are used to collect gaseous mercury in flue gas during stationary source emissions testing.<ref>Code of Federal Regulations(7-1-07) Edition, Title 40, Part 60, Appendix A-8, Method 29, Section 7.3.1</ref>
In histology, potassium permanganate was used as a bleaching agent.<ref name="Picken_2010">Template:Cite journal</ref><ref name="Murphy_2001">Template:Cite journal</ref>
Fruit preservation
Ethylene absorbents extend storage time of bananas even at high temperatures. This effect can be exploited by packing bananas in polyethylene together with potassium permanganate. By removing ethylene by oxidation, the permanganate delays the ripening, increasing the fruit's shelf life up to 4 weeks without the need for refrigeration.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
The chemical reaction, in which ethylene (C2H4) is oxidised by potassium permanganate (KMnO4) to carbon dioxide (CO2), manganese oxide (MnO2) and potassium hydroxide (KOH), in the presence of water, is presented as follows:<ref>Template:Cite journal</ref>
3 C2H4 + 12 KMnO4 + 2 H2O → 6 CO2 + 2 H2O + 12 MnO2 + 12 KOH
Survival kits
Potassium permanganate is sometimes included in survival kits: as a hypergolic fire starter (when mixed with glycerol antifreeze from a car radiator);<ref name="Bob Gillis and Dino Labiste">Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref> as a water sterilizer; and for creating distress signals on snow.<ref>Template:Cite journal</ref> Modern hiking and survivalist guides advise against using potassium permanganate in the field because it is difficult to dose correctly.<ref name="Vogel"/>
Fire service
Potassium permanganate is added to "plastic sphere dispensers" to create backfires, burnouts, and controlled burns. Polymer spheres resembling ping-pong balls containing small amounts of permanganate are injected with ethylene glycol and projected towards the area where ignition is desired, where they spontaneously ignite seconds later.<ref name=usfs>Template:Cite web</ref><ref name=dj>Template:Cite episode</ref> Both handheldTemplate:R helicopter-Template:R unmanned aircraft systems (UAS) or boat-mountedTemplate:R plastic sphere dispensers are used.
Other uses
Potassium permanganate is one of the principal chemicals used in the film and television industries to "age" props and set dressings. Its ready conversion to brown MnO2 creates "hundred-year-old" or "ancient" looks on hessian cloth (burlap), ropes, timber and glass.<ref>Template:Cite journal</ref>Template:Primary source inline
Potassium permanganate is used as an oxidizing agent in the synthesis of cocaine and methcathinone.<ref>Template:Cite journal</ref> It can purify cocaine paste with oxidization to increase its stability. This led to the Drug Enforcement Administration launching Operation Purple in 2000, with the goal of monitoring the world supply of potassium permanganate; however, potassium permanganate derivatives and substitutes were soon used thereafter to avoid the operation.<ref>Template:Cite news</ref>
History
In 1659, Johann Rudolf Glauber fused a mixture of the mineral pyrolusite (manganese dioxide, MnO2) and potassium carbonate to obtain a material that, when dissolved in water, gave a green solution (potassium manganate) which slowly shifted to violet and then finally red.<ref>Template:Cite book</ref><ref>Template:Cite web</ref><ref>Translated in: Template:Cite book</ref> The reaction that produced the color changes that Glauber observed in his solution of potassium permanganate and potassium manganate (K2MnO4) is now known as the "chemical chameleon".<ref>Template:Cite web</ref>
The case of the chameleon mineral alludes to a broader reflection on how epistemological framework dictates what early modern scientists perceived as meaningful discoveries.<ref>Template:Cite journal</ref> Little literature exists on Glauber’s accidental discovery of potassium permanganate and the importance of both its dismissal and its conversion into a modern medical and hygienic staple.
The earliest description of the production of potassium permanganate is here.<ref>Template:Cite book</ref> Just under 200 years later, London chemist Henry Bollmann Condy had an interest in disinfectants; 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 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 Condy was subsequently forced to spend considerable time in litigation to stop competitors from marketing similar products.<ref>Template:Cite journal</ref> According to Varlam Shalamov, potassium permanganate solution was used as a catch-all treatment for dysentery, frostbite and ulcers in the Gulag camps of Kolyma.
Early photographers used it as a component of flash powder. It is now replaced with other oxidizers, due to the instability of permanganate mixtures.Template:Citation needed
Preparation
Potassium permanganate is produced industrially from manganese dioxide, which also occurs as the mineral pyrolusite. In 2000, worldwide production was estimated at 30,000 tonnes.<ref name="Ullmann">Template:Ullmann</ref> The MnO2 is fused with potassium hydroxide and heated in air or with another source of oxygen, like potassium nitrate or potassium chlorate.<ref name="Ullmann"/> This process gives potassium manganate:
With sodium hydroxide, the end product is not sodium manganate but a Mn(V) compound, which is one reason why the potassium permanganate is more commonly used than sodium permanganate. Furthermore, the potassium salt crystallizes better.<ref name="Ullmann"/>
The potassium manganate is then converted into permanganate by electrolytic oxidation in alkaline media:
Other methods
Although of no commercial importance, potassium manganate can be oxidized by chlorine or by disproportionation under acidic conditions.<ref>Template:Cite book</ref> The chlorine oxidation reaction is
and the acid-induced disproportionation reaction may be written as
A weak acid such as carbonic acid is sufficient for this reaction:
Permanganate salts may also be generated by treating a solution of Mn2+ ions with strong oxidants such as lead dioxide (PbO2), sodium bismuthate (NaBiO3), or peroxydisulfate. Tests for the presence of manganese exploit the vivid violet color of permanganate produced by these reagents.
Reactions
Organic chemistry
Dilute solutions of KMnO4 convert alkenes into diols. This behaviour is also used as a qualitative test for the presence of double or triple bonds in a molecule, since the reaction decolorizes the initially purple permanganate solution and generates a brown precipitate (MnO2). In this context, it is sometimes called Baeyer's reagent. However, bromine serves better in measuring unsaturation (double or triple bonds) quantitatively, since KMnO4, being a very strong oxidizing agent, can react with a variety of groups.
Under acidic conditions, the alkene double bond is cleaved to give the appropriate carboxylic acid:<ref>Template:OrgSynth</ref>
Potassium permanganate oxidizes aldehydes to carboxylic acids, illustrated by the conversion of n-heptanal to heptanoic acid:<ref>Template:OrgSynth</ref>
Even an alkyl group (with a benzylic hydrogen) on an aromatic ring is oxidized, e.g. toluene to benzoic acid.<ref>Template:Cite journal</ref>
Glycols and polyols are highly reactive toward KMnO4. For example, addition of potassium permanganate to an aqueous solution of sugar and sodium hydroxide produces the chemical chameleon reaction, which involves dramatic color changes associated with the various oxidation states of manganese. A related vigorous reaction is exploited as a fire starter in survival kits. For example, a mixture of potassium permanganate and glycerol or pulverized glucose ignites readily.<ref name="Bob Gillis and Dino Labiste"/> Its sterilizing properties are another reason for inclusion of KMnO4 in a survival kit.Template:Citation needed
Ion exchange
Treating a mixture of aqueous potassium permanganate with a quaternary ammonium salt results in ion exchange, precipitating the quat salt of permanganate. Solutions of these salts are sometimes soluble in organic solvents:<ref>Template:Cite journal</ref>
Similarly, addition of a crown ether also gives a lipophilic salt.<ref>Template:Cite journal</ref>
Reaction with acids and bases
Permanganate reacts with concentrated hydrochloric acid to give chlorine and manganese(II):
In neutral solution, permanganate slowly reduces to manganese dioxide (MnO2). This is the material that stains one's skin when handling KMnO4.
KMnO4 reduces in alkaline solution to give green K2MnO4:<ref>Template:Cite book</ref>
This reaction illustrates the relatively rare role of hydroxide as a reducing agent.
Addition of concentrated sulfuric acid to potassium permanganate gives Mn2O7.<ref>Template:Cite book</ref> Although no reaction may be apparent, the vapor over the mixture will ignite paper impregnated with alcohol. Potassium permanganate and sulfuric acid react to produce some ozone, which has a high oxidizing power and rapidly oxidizes the alcohol, causing it to combust. As the reaction also produces explosive Mn2O7, this should only be attempted with great caution.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Thermal decomposition
Solid potassium permanganate decomposes when heated:<ref name="k821"/>
It is a redox reaction.Template:Cn
Safety and handling
Potassium permanganate poses risks as a strong<ref name="k821"/> oxidizer.<ref name="Bretherick_2007">Template:Cite book</ref> Contact with skin can cause skin irritation, skin and mucous membrane corrosion,<ref name="k821"/> and in some cases severe allergic reaction.Template:Cn It is poisonous to humans and animals, and ingestion may lead to respiratory failure.<ref name="Schonwald_2004"/> It is incompatible with organic and readily oxidized materials and poses a violent reaction and explosion hazard. It is flammable during some chemical reactions and emits toxic fumes when burning.<ref name="k821"/>
It can also result in discoloration and clothing stains.<ref>Template:Cite web</ref>
References
Bibliography
- Template:Cite book Access this document via National Service Center for Environmental Publications (NSCEP), pubnumber 815R99014
- Template:Cite book
- Template:Cite book
Further reading
External links
Template:Permanganates Template:Manganese compounds Template:Potassium compounds Template:Antiseptics and disinfectants Template:Antidotes Template:Organic reactions Template:Portal bar