Potassium permanganate (KMnO4)

Potassium permanganate (CAS 7722-64-7; molar mass approximately 158.03 g/mol) is the potassium salt of permanganic acid. The permanganate ion (MnO4−) gives the compound its characteristic deep purple colour and its strong oxidising power. Its reduction products depend on pH: typically Mn2+ in acidic conditions and manganese dioxide (MnO2) in neutral or mildly alkaline conditions.

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What is potassium permanganate used for?

In analytical laboratories it is the titrant in permanganometry, a class of redox titrations used to determine iron(II), oxalate, hydrogen peroxide and other reducing species. The titration is self-indicating because the faint pink of excess permanganate marks the end point. KMnO4 is not a primary standard, so its solutions are usually standardised, for example against sodium oxalate. Industrial and municipal uses include oxidation of iron, manganese and taste- or odour-causing compounds in water treatment. It is also used as an oxidant in organic synthesis and as a stain for thin-layer chromatography.

Which grades and documents should buyers expect?

KMnO4 is supplied in technical, laboratory and analytical (for example ACS reagent) grades. Some pharmacopoeial monographs also exist. Buyers should request a CoA that states assay and impurity limits, together with a current SDS.

How is it classified and regulated?

Under GHS it is classified as an oxidising solid that may intensify fire. It is harmful if swallowed and very toxic to aquatic life with long-lasting effects. Consult the supplier SDS for the complete classification. For transport it is UN 1490, Class 5.1. It must be kept away from combustible materials, reducing agents and concentrated acids. Potassium permanganate is listed in Table I of the UN 1988 Convention against illicit drug trafficking and is a scheduled drug precursor in the EU and many other jurisdictions. As a result, sales may require customer declarations, licensing or registration.

Related concepts

Related topics include oxidising agents, redox titration, manganese dioxide, primary standards, sodium oxalate, potassium dichromate and drug precursor control.