Prep. Chlorate of potash and oxide of manganese, in fine powder, are mixed together; caustic potash, dissolved in a small quantity of water, is added, and the whole evaporated to dryness, and then exposed to a dull red heat for an hour, till it has assumed the condition of a semi-fused mass. This mass is pulverized, boiled with water, and the liquid decanted, and accurately neutralized with sulphuric acid; it is then evaporated, and the permanganate allowed to crystallize.

Prop. & Comp. Permanganate of potash occurs in the form of red or dark purple acicular crystals, sometimes reflecting a metallic green colour, and having a sweet astringent taste. A single small crystal is sufficient to colour an ounce of water deep purple, which, when mixed with a little rectified spirit and heated, is changed to a yellowish brown. This is due to the deoxidation of the acid by the organic matter and its reduction to the state of binoxide of manganese. The crystals evolve oxygen gas when heated, and leave a black residue in which the presence of potash may be detected by the usual tests. Five grains dissolved in water, require for complete decoloration a solution of 44 grains of granulated sulphate of iron, acidulated with 2 fluid drachms of dilute sulphuric acid. In this decomposition, the sulphate of the protoxide of iron absorbs oxygen from the permanganate, and becomes converted into a per-salt with the aid of the additional sulphuric acid present.

Off. Prep. Liquor Potassae Permanganatis. Solution of Permanganate of Potash. [Not officinal in U. S. P.] (Permanganate of potash, four grains; distilled water, one fluid ounce.)

Therapeutics. Permanganate of potash is a powerful anti- septic agent, and as such can be employed with much advantage in the form of a gargle or lotion to remove decomposing matter and clean diseased surfaces. Administered internally, it has been proposed as a remedy in diabetes.

Dose. 1 gr. to 4 gr. if given internally. Externally, 1 fl. drm. of the solution to 5 or 10 oz. of water.

Bichromate of Potash. Appendix A.

Prop. & Comp. Bichromate of potash is met with in large red transparent four-sided tables. It is soluble in water; the aqueous solution gives with chloride of barium a yellowish-white precipitate (chromate of baryta), and with nitrate of silver an orange precipitate (chromate of silver), both of which are soluble in nitric acid. The composition of the bichromate of potash is represented by the formula, KO, 2 Cr O3.

Therapeutics. Never employed as a medicine.

Off. Prep. The bichromate is used for making a volumetric solution for the estimation of the protosalts of iron. An explanation of its action when thus employed will be found among the volumetric solutions.