Potassium Permanganate

Description

Potassium permanganate is the chemical compound KMnO4. In this salt, manganese is in the +7 oxidation state. The salt is also known as "permanganate of potash" and "Condy's crystals". The permanganate ion is a strong oxidizing agent. It dissolves in water to give deep purple solutions, evaporation of which gives prismatic purple-black glistening crystals.[1] It has a sweet taste and is odorless.

Chemical applications

Potassium permanganate is used as an oxidizing agent in diverse chemical reactions in the laboratory and in industry.[2] It also serves as a disinfectant and in deodorizers. It can be used as a reagent for the synthesis of many different kinds of chemical compounds. In wastewater treatment, it is used to neutralize hydrogen sulfide. In analytical chemistry, a standardized aqueous solution of KMnO4 is sometimes used as an oxidizing titrant for redox titrations due to its deep purple color. In a related way, it is used as a reagent to determine the Kappa number of wood pulp.
As an oxidant in organic synthesis
Dilute solutions of KMnO4 convert alkenes into diols (glycols). This behavior is also used as a qualitative 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.
Concentrated solutions oxidize a methyl group on an aromatic ring, e.g. toluene to benzoic acid.
KMnO4 oxidizes pseudoephedrine hydrochloride to produce methcathinone, a Schedule I drug in the United States. Consequently the DEA has restricted its use and sale by classifying it as a List I controlled precursor. Potassium permanganate is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.[1]
Acids and KMnO4
Concentrated sulfuric acid reacts with KMnO4 to give Mn2O7, which can be explosive.[3]. Similarly concentrated HCl gives chlorine. The Mn-containing products from redox reactins depend on the pH. Acidic solutions of permanganate are reduced to the faintly pink [Mn(H2O)6]+2. In neutral solution, permanganate is only reduced by 3e- to give a brown precipitate of MnO2, wherein Mn is in a +4 oxidation state. This is the material that stains one's skin when handling KMnO4. KMnO4 spontaneously reduced in an alkaline solution to green-coloured K2MnO4, wherein manganese is in the +6 oxidation state.
A curious reaction is observed when one adds concentrated sulfuric acid to potassium permanganate. 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 oxidising power and rapidly oxidises the alcohol, causing it to combust. An approximate equation for the ozone formation is shown below.
6 KMnO4 + 9 H2SO4 → 6 MnSO4 + 3 K2SO4 + 9 H2O + 5 O3
The H2SO4/KMnO4 reaction can also produce the oily Mn2O7, which is unstable and can decompose explosively.[4][5]
Biomedical uses
· Dilute solutions are used as a treatment for canker sores (ulcers) (0.25%), disinfectant for the hands (about 1%) and treatment for mild pompholyx dermatitis or fungal infections of the hands or feet.
· A dilute solution of acidified potassium permanganate is used in histology to bleach melanin which obscures tissue detail.
· Potassium permangante can 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

Miscellaneous uses

· Aqueous solutions of KMnO4 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 still used in torpedoes.
· A dilute (10mg/l) of potassium permanganate can be used to eliminate snails from plants prior to placing them in a fresh-water aquarium.
· High-grade potassium permanganate can be found at pool supply stores and is used in rural areas to remove iron and hydrogen sulfide (rotten egg smell) from well water.
· KMnO4 is often included in survival kits along with either glycerine or a glucose tablet for the purposes of making fire. The glucose tablet can be ground up, mixed with the potassium permanganate and caused to combust by applying friction. It can also be mixed with anti-freeze from a vehicle to produce flame, although this can be dangerous and should be done in a controlled manner ie dipping some paper into the anti-freeze and then adding a small amount of potassium permanganate. The ability to sterilise water and wounds is also advantageous and another reason for inclusion in a survival kit.
· KMnO4 is employed to treat some parasitic diseases of fish, in treatment of drinking water, as well as an antidote in phosphorus poisoning. In Africa, it has been used to as a disinfectant for vegetables such as lettuce.

Norkem Limited provides the information contained herein in good faith but makes no representation as to its comprehensiveness or accuracy.
Individuals receiving the information must exercise their independent judgment in determining its appropriateness for a particular purpose