Caustic Potash. - Hydrate of potassium, KHO, containing some impurities.

Characters. - In hard white pencils, very deliquescent, powerfully alkaline and corrosive.

Reactions and Tests. - A watery solution gives the reactions of potassium (p. 603) and those showing the absence of impurities.

Pkeparation containing Caustic Potash. Liquor Potasssae...............27 grains in 1 fluid ounce.

Pbeparation in which Caustic Potash is used. Potassii Permanganas.

Uses. - It is used as a caustic where we wish to burn deeply and widely, as in snake-bites, the bites of rabid animals, or in poisoned wounds. It is occasionally employed to open abscesses, more especially abscess of the liver, in which it is sometimes preferred to the knife, as by its use we secure adhesion of the liver to the abdominal wall before the abscess is opened, and thus prevent any pus from finding its way into the peritoneal cavity. Ringer says that the best way to apply it is to cut a hole in a thick piece of plaster, smaller than the size of the slough which we wish to make, and rub on the caustic potash, slightly wetted until the tissues assume a greyish colour, then to wash the part with vinegar, and apply a poultice. Solutions of caustic potash of the strength of 10 to 30 grains to the ounce of distilled water are useful in dissolving the thickened patches of old eczema: acetic acid must be applied to neutralise the potash, and the treatment renewed once or twice a week.