Potassium permanganate is the inorganic chemical compound KMnO4, a water soluble salt consisting of equal mole amounts of potassium (K+) and permanganate (MnO4-, officially called manganate (VII) ) ions. This salt, formerly known as permanganate of potash or Condy's crystals is a strong oxidizing agent. It dissolves in water to give deep purple solutions, evaporation of which gives prismatic purplish-black glistening crystals.
It forms orthorhombic crystals with constants: a = 9.105, b = 5.720, c = 7.425 Ã…. The Mn-O bond distances are 1.629 Ã….
Potassium permanganate is useful in the following dermatological conditions:
Infected eczema and blistering skin conditions
Wound cleansing, especially weeping ulcers or abscesses
Fungal infections such as athlete's foot.
Potassium permanganate baths are effective for the treatment of infected eczema when there are blisters, pus and/or oozing. A potassium permanganate concentration of 1:10,000 should be used (pink colour). If using 400 mg tablets, add one to each 4 L of water. The tablets should be dissolved in hot water before pouring into the bath. Twice daily baths for two days help to dry out the weeping sores and soothe the eczema.
A potassium permanganate solution of 1 in 1,000 may be used as wet soaks to blistering wounds such as ulcers and abscesses. Strips of cotton or gauze should be soaked in the solution and wrapped around the affected area for 20–30 minutes. The astringent action of potassium permanganate helps to dry out the blister and prepare the wound for other treatment.
A 1% solution (1 in 100) is used to treat fungal infections such as athlete's foot.
Precautions when using potassium permanganate
Almost all applications of potassium permanganate exploit its oxidizing properties. As a strong oxidant that does not generate toxic byproducts, KMnO4 has many niche uses.
Potassium permanganate is one of the principle chemicals utilised in the film and television industries (Art Department) in order to "Age" props and set dressings. The oxidising effects of PP can create very effective looks on hessian cloth, ropes, timber and glass which create a "hundred year old" or "ancient" look. It was used on props and sets in Films such as "Troy", "300" and "Indiana Jones" to achieve just this.
Disinfectant and water treatment
As an oxidant, potassium permanganate can act as a disinfectant. For example, dilute solutions are used to treat canker sores (ulcers), disinfectant for the hands and treatment for mildpompholyx, dermatitis, and fungal infections of the hands or feet. Potassium permanganate, obtainable at pool supply stores, is used in rural areas to remove iron and hydrogen sulfide(rotten egg smell) from well and waste water. Historically it was used to disinfect drinking water.
Related to the use of KMnO4 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.In histology, it is used 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.Permanganate washes were once used to treat gonorrhea and are still used to treat candidiasis.
Aside from its use in water treatment, the other major application of KMnO4 is as a reagent for the synthesis of organic compounds. Significant amounts are required for the synthesis of ascorbic acid, chloramphenicol, saccharine, isonicotinic acid, and pyrazinoic acid.
Potassium permanganate can be used to quantitatively determine the total oxidisable organic material in an aqueous sample. The value determined is known as the permanganate value. Inanalytical chemistry, a standardized aqueous solution of KMnO4 is sometimes used as an oxidizing titrant for redox titrations. 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.
Dilute solutions of KMnO4 convert alkenes into diols (glycols). This behaviour is also used as a qualitative test for the presence of double or triple bonds in a molecule, since the reaction decolourises 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 KMnO4, being a very strong oxidizing agent, can react with impurities in a sample.
Under acidic conditions, the alkene double bond is cleaved to give the appropriate carboxylic acid:
CH3(CH2)17CH=CH2 + [O] → CH3(CH2)17COOH
Potassium permanganate oxidizes aldehydes to carboxylic acids, such as the conversion of n-heptanal to heptanoic acid:
C6H13CHO + [O] → C6H13COOH
Even an alkyl group (with a benzylic hydrogen) on an aromatic ring is oxidized, e.g. toluene to benzoic acid.
Glycols are highly reactive toward KMnO4. 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 KMnO4 in a survival kit.