This is a very important salt, which has but recently gained the reputation which it merits. I am acquainted with no non-volatile disinfecting agent which equals it at once in the efficiency and facility of its action. Though long known to chemists, it is only within a few years that it has been employed as a medicine, having been brought to the notice of the profession by Mr. Condy in 1851, as a powerful disinfectant, and as probably capable of extensive remedial application. it was first used in England, in solution, under the name of Condy's Disinfecting Fluid, it is prepared in various methods, in all of them from bromide of manganese and hydrate of potassa, which are exposed to heat, and then generally brought to a higher state of oxidation by a supply of oxygen. The simplest plan is that of Dr. Squibb, by which the oxygen necessary to bring the binoxide of manganese into the state of oxidation requisite to form the permanganic acid, is furnished by one portion of the binoxide to another portion. Potassa and the binoxide are heated together, and then repeatedly subjected to the action of water with heat, being dried after each addition of water except the last, which is decanted. The residue is twice treated in the same way; after which the clear liquids are mixed, and cautiously evaporated so that they shall crystallize on cooling. The crystals having been separated and dried, constitute the salt in question. For further particulars of the operation the reader is referred to the 12th edition of the U. S. Dispensatory. in the first step of the process, a portion of the binoxide gives up to another portion sufficient oxygen to convert the latter into manganic acid, which unites with the potassa to form the manganate. This is dissolved out by the water; and when in solution, its manganic acid divides itself into two parts, one of which is converted back into the binoxide by giving up an equivalent of oxygen to two equivalents of the other part, thereby converting this into the permanganic acid (Mn207), which remains combined with the one eq. of potassa, constituting the permanganate (KO,Mn207). Properties. Permanganate of potassa, when crystallized, is in slender prismatic crystals, of a dark-purplish colour; but when obtained by the evaporation of its solution to dryness, has the form of an intensely black powder. it is inodorous, and of a sweetish, astringent taste. Water dissolves it freely, forming a solution which, when concentrated, is blackish-purple, and almost opaque from the density of its colour, but when diluted, is perfectly transparent, and of a beautiful red with a hya-cinthine or lilac hue. Moderately heated, the crystals are partially volatilized, giving out violet vapours, which have an unpleasant metallic odour. Suddenly heated, they detonate, and evolve oxygen; a dark powder being left, which gives evidence of the presence of potassa to the tests of that alkali. The most remarkable property of the permanganate is the facility with which it parts with oxygen, and its consequent extraordinary power of oxidizing other bodies. in consequence of the unusual degree in which it possesses the power, it is supposed to hold its oxygen in the state of ozone, or in other words to be an ozonide. it is very probable that a portion of the oxygen escaping from it may be in the state of ozone; but that the whole, or any considerable portion of it, is so, seems contradictory to the laws of ozone itself, which admit but a small proportion of this principle to exist in isolated oxygen, or air containing it. The presence of ozone is not, however, essential to the explanation of its powers; the great facility with which the salt parts with oxygen, and the nascent state of this element when separated, being sufficient to account for the result. Almost any kind of organic matter decomposes it, even that existing in the air in its purest natural state; and hence the necessity of keeping it in perfectly clean glass bottles, with well-fitting glass stoppers. I have known a strong solution of it to be rendered wholly unfit for use by being introduced into an ordinary glass bottle, which to the eye appeared as clean as usual, but to the sides of which organic matter must have been adhering. Even in the purest state in which it is kept in the shops, it is apt, when dissolved, to leave a small insoluble residue, owing to the decomposition produced by organic matter in the atmosphere even in the dry state. indeed, a solution of it may be used as a test of atmospheric purity, as regards substances of organic origin; the rapidity and amount of the production of insoluble matter, indicating the degree of impurity. Some very inflammable substances take fire spontaneously in its presence; and there is scarcely any organic body which will resist its oxidizing powers; not even those which ozone will not affect, as the non-nitrogenous vegetable acids, glycerin, and the proper, animal excretions, as urea, etc. The organic alkaloids and their salts are decomposed by it; and hence it was proposed by Condy as an antidote to various poisons. Most oxidizable mineral substances, and those which, being already in the condition of oxides, are disposed to pass to a higher state of oxidation, decompose it, including iodine and the iodides, the arsenites, and all the metallic salts, the bases of which are capable of being peroxidized, especially the proto-salts of iron.

It is on the same property that its powerful disinfecting agency depends. it destroys the organic compounds formed during vegetable and animal decomposition; while the products of its own action are perfectly inoffensive; and consequently it entirely obviates the offensive odour and noxious influence of putrefaction. The power has been claimed for it of destroying the matter of contagion; but this has not been satisfactorily demonstrated; and the probability is that its influence is purely chemical, and not to be depended on for the destruction of living germs, or the vital organizations which are probably the agents of contagion and infection.