PERMANGANATES, compounds of permanganic acid with bases. If to perman ganates of potash,. free from excess of alkali, a large quantity of water is added, it is decomposed iuto hydrated dioxide of manganese and permanganate of potash, which latter remains in solution while the dioxide is precipitated. The following equation rep resents the reaction: Remarkable changes of color accompany the decomposition, on which account this per manganate has been called mineral chameleon. Excess of alkali in the manganate confers more stability upon it, retarding the decomposition. On a large kale permanganate of potash is made by mixing equal parts of finely powdered dioxide of manganese and chlorate of potash with rather more than one part of caustic potash dissolved in a little water, evaporating to dryness, and then heating to a point just below ignition. This mass is then treated with hot water, the insoluble oxide separated by decantation, and the purple liquid concentrated by evaporation until crystals form upon the surface. It is then left to cool and complete the process of crystallization. The crystals have a dark purple color and are not very soluble in water. The manganates and permanganates are decomposed when brought into contact with organic matter. The manganates are iso
morphous with the sulphates, whilst the permanganates are isomorphous with the per chlorates. Condy's disinfecting fluids, sold in the drug shops, are alkaline manganates and permanganates. Permanganate of hydrogen or permanganic acid, is obtained by dissolving permanganate of potash in sulphuric acid, with one mole cule of water added, and distilling the solution between 140° and 158° F. The acid passes over in violet vapors, and condenses in a greenish-black liquid having a metallic luster, a strong attraction for moisture and for oxygen, setting fire to paper, etc. and to alcohol. AValer is colored with a small amount of the permanganates, and such solutions are very delicate tests for deoxidizing matters, because these latter the color by reducin the permanganate. A weak solution of a permanganate is used the labora tory for determiningthe amount of oxidizable substances. The contaminations of drink ing waters produced by septic fermentation are easily detected by using permanganates as reagents, and it is in consequence of their great oxidizing power that the permanga nates are good disinfectants.