Potassium permanganate
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| Potassium permanganate | |
|---|---|
| Image:Kaliumperma.jpg | |
| General | |
| Other names | Potassium manganate(VII) |
| Molecular formula | KMnO4 |
| Molar mass | 158.04 g/mol |
| Appearance | purple solid |
| CAS number | [7722-64-7] |
| Properties | |
| Density and phase | 2.703 g/cm3, solid |
| Solubility in water | 6.38 g/100 ml (20 °C) |
| Melting point | 270 °C decomp. |
| Thermodynamic data | |
| Standard enthalpy of formation ΔfH°solid | −813.4 kJ/mol |
| Standard molar entropy S°solid | 171.7 J.K−1.mol−1 |
| Hazards | |
| EU classification | Oxidant (O) Harmful (Xn) Dangerous for the environment (N) |
| NFPA 704 | Image:Nfpa h1.pngImage:Nfpa f0 ox.pngImage:Nfpa r0.png |
| R-phrases | R8, R22, R50/53 |
| S-phrases | S2, S60, S61 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Regulatory data | Flash point, RTECS number, etc. |
| Related compounds | |
| Other anions | Potassium perrhenate |
| Other cations | Sodium permanganate |
| Related compounds | Potassium manganite Potassium manganate Manganese heptoxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Potassium permanganate (KMnO4) is an inorganic chemical compound composed of potassium (K+) and permanganate (MnO4-) ions. Its IUPAC name is potassium manganate(VII) because its manganese (Mn) atom is in the +7 oxidation state. It is also known as "permanganate of potash", "Potassium Salt" and "Condy's crystals". The permanganate acts as a strong oxidizing agent. The molecular weight of potassium permanganate is 158.04 g/mol. As a solid, it forms deep purple prisms. It is purple when dissolved in an aqueous solution. It has a sweet taste and is odorless.
Contents |
History
Potassium permanganate was discovered in 1659.
Early photographers used it as a component of flash powder.
Uses
Potassium permanganate is used as an oxidizing agent in many different kinds of chemical reactions in a laboratory and in industry. It is also used as a disinfectant and in deodorizers. It is used to treat some parasitic diseases of fish, and used in treatment of drinking water, as well as an antidote in phosphorus poisoning. It can be used as a reagent for the synthesis of many different kinds of chemical compounds. For example, a dilute solution of KMnO4 can convert an organic compound with a carbon-carbon double bond into a diol (glycol) compound. Stronger permanganate solutions can oxidize a methyl group on an aromatic ring to a carboxyl group. It has also been used to make cocaine 100% pure. 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. Deep purple-colored permanganate can be reduced to the faintly pink Mn+2 cation in an acidic solution, where Mn is in a +2 oxidation state. In an alkaline solution, permanganate is only reduced to MnO2, a brown precipitate in which Mn is in a +4 oxidation state.
An aqueous solution of potassium permanganate can be mixed with an aqueous solution of pseudoephedrine hydrochloride to produce methcathinone.
In a diluted solution, it can be used as a mouthwash (1/4%), or to disinfect the hands (1%).
In aqueous solution was used as together with T-Stoff (i.e. 80 % hydrogen peroxide) as propellant for the rocket plane Messerschmitt Me 163. In this usage, it is known as Z-Stoff. This combination of propellants is still used in torpedoes.
It is used as a reagent to determine the Kappa number of wood pulp.
Cautions
Solid KMnO4 is a very strong oxidizer, which when mixed with pure glycerine, will cause a highly exothermic chemical reaction to take place. This reaction would turn red hot as a spontaneous "combustion" which would melt a glass or other container holding the reacting contents and could ignite anything flammable nearby. A reaction of this sort could take place when solid KMnO4 is mixed with many kinds of organic materials. Aqueous solutions of KMnO4 are much less dangerous, especially when diluted. Mixing solid KMnO4 with concentrated sulfuric acid forms Mn2O7 which causes an explosion.[1] Also, it should never be left near petrol (gasoline) or any such readily oxidisible substance.
Potassium permanganate stains the hand and clothing and should be handled with care. Clothing stains may be washed away using acetic acid or hydrochloric acid. Skin stains disappear within 48 hours. In addition, mixing solid KMnO4 with concentrated hydrochloric acid generates dangerous chlorine gas. [1]
The DEA has restricted its use and sale. Moreover, potassium permanganate is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances[2].
Reactions
Alkaline + hydroxy group + potassium permanganate under acidic conditions will produce two carboxylic acids.
Reference
- 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
