The only salt of this metal in the Pharmacopoeia is the black oxide; but permanganate of potash, which is derived from it, is best discussed under this head.

Manganesii Oxidum Nigrum. - Black Oxide of Manganese. MnO2. A heavy black powder.

From Manganesii Oxidum Nigrum is made:

Potassae Permanganas. - Permanganate of Potash. KMnO4.

Source. - Made by (1) evaporating a mixture of Black Oxide of Manganese, Chlorate of Potash, and Caustic Potash in water, pulverising the residue, heating it to redness, cooling and pulverising; then (2) boiling in "Water, neutralising with Diluted Sulphuric Acid, and evaporating. (1) 3MnO2 + KC1O3 + 6KHO = 3K2MnO4 + KC1 + 3H1O; a manganate being formed. (2) 3K2MnO4 + 2H1O = 2KMnO4 + 4KHO + MnO2; the manganate becoming permanganate by boiling.

Characters. - Dark purple, slender prisms, inodorous, with a sweet astringent taste, yielding an intense purple solution when moistened. Solubility, 1 in 16 of water. Is very rapidly deoxydised in the presence of organic matter into hydrated peroxide of manganese, losing its purple colour for a brown.

Impurities. - Sulphate of potash, and black oxide of manganese; detected by being less soluble in water, and by volumetric test.

Dose. - 1 to 2 gr.

Liquor Potassae Permanganatis. - 4 gr. to 1 fl.oz. Lose, 2 to 4 fl.dr. Manganesii Oxidum Nigrum is also used in making Liquor Chlori and Hydrargyri Perchloridum.

Action And Uses. 1. Immediate Local Action And Uses

Externally. - Permanganate of potash is an irritant or eseharotic in the pure state, stimulant in the form of the solution, and has a healing effect upon scars and wounds. The principal applications, however, are independent of its physiological action on the human tissues, and due to its influence as an antiseptic, disinfectant, and deodorant, that is, to its action on the processes and products of sepsis, fermentation, and decomposition. By its power of giving up oxygen freely, the permanganate either destroys the ferment or organism on which these processes depend, or forms chemical compounds with the materials on which they flourish (the tissues, plasma, pus, etc.), incapable of decomposition: it is thus an antiseptic. By similarly oxydising the products of decomposition already begun, it so alters their chemical properties as to deodorise and decolorise them, and possibly destroys also the power of further infection which such products generally possess: it is thus a disinfectant. Permanganate of potash may therefore be used as a dressing for foul ulcers; but other substances, possessing special advantages, are generally preferred for this pur}..

Internally. - This salt is employed as a mouth-wash in foul condition of the teeth and mouth, as a gargle in putrid sore-throat, and as an injection in infective and foul discharges, such as gonorrhoea, vaginitis, ozosna, and cancer of the uterus.

2. Action In The Blood, Specific Action, And Remote Local Action

Nothing is definitely known of the action of permanganic acid on the blood, tissues, or organs of excretion. It is difficult to believe that any portion of the salt escapee decomposition before absorption, unless given in poisonous doses; and the oxide of manganese, into which it is converted, is believed to be inert. The internal administration of the potash salt for some supposed effect on infective fevers or gangrenous pro-cesses must therefore be useless. It has recently been used as an emmenagogue in amenorrhoea.

By far the most important application of permanganate of potash is as a disinfectant and deodorant, apart from the human body: to disinfect stools and foul discharges after removal from the patient; to wash utensils; and to flush water-closets, etc. Its great advantages are, that it is rapid and complete in its action; odourless and non-poisonous in solutions of ordinary strength; and that it shows by change of colour whether it is acting or exhausted. The principal disadvantage connected with it is its expense.