Characters. - Dark purple, slender, prismatic crystals, inodorous, with a sweet astringent taste.

Preparation. - By heating caustic potash and manganese dioxide together in a crucible with chlorate of potassium which yields up its oxygen to the manganese and forms manganate of potassium, 3MnO2 + 6KHO + KC1O3=3K2MnO4 + KCl + 3H2O. On boiling this with water it is decomposed, permanganate being formed, and manganese dioxide being deposited. 3K2MnO4 + 2H2O = K2Mn2O8 + MnO2 + 4KHO. On decanting from the manganese dioxide, neutralising with sulphuric acid, evaporating, filtering through asbestos, and evaporating further, the salt crystallises out.

Solubility. - It is entirely soluble in cold water. A single small crystal suffices to form with an ounce of water a rich purple solution.

Reactions. - It gives off oxygen readily to organic substances and is decomposed, manganese dioxide being precipitated, so that the solution when mixed with a little rectified spirit and heated, becomes yellowish-brown.. The crystals heated to redness decrepitate, evolve oxygen gas, and leave a black residue from which water extracts potash, recognised by its alkaline reaction and by the appropriate tests.

Preparation.

S.P. liquor Potassii Permanganatis (Permanganate of Potassium 4.4 grs. in 1 fl. oz. of water or 1 per cent. solution). Condy's fluid is a solution of 2 grains to the ounce.

Administration. - The solution has a disagreeable taste, and the solid permanganate of potassium gives off oxygen so readily that, if mixed with easily oxidisable substances, such as sugar, syrup, or glycerine, the mixture may explode or take fire spontaneously. Martindale recommends that the necessary quantity of permanganate should be made into a pill with kaolin ointment consisting of equal parts of vaseline, paraffin, and kaolin.

Action. - Permanganate of potassium very readily parts with its oxygen, and thus destroys organic matter; when mixed with cobra poison it completely destroys the deadly power of the latter, and the mixture may be injected subcutaneously without any bad effects. When injected after the poison, however, it does not appear to come into such immediate contact with it in the tissues as to destroy it, and it therefore does not act as an antidote.

Uses. - It is used to disinfect the stools in typhoid fever, and to disinfect the hands after making post-mortem examination, or after coming in contact with matters likely to convey contagion or infection (p. 105). It is applied as a lotion to wounds and sores, especially those having a foul-smelling discharge, and may be injected into the cavity of abscesses after evacuation of pus, or used to wash out the cavity of the pleura after the fluid has been removed in cases of pleurisy. In cases of ozaena it is employed to wash the nose, and as a lotion or gargle to the mouth in ulceration with foetor, such as mercurial stomatitis, and also in diphtheria. It has been recommended internally in cases of diabetes. It is said by Ringer and Murrell to be of very great use in amenorrhoea, two or three grains being given in pill three or four times a day for some days before the period.