Potassium. • = KC1 + 60.
It is not very soluble, as it requires for its solution 16 parts of cold and 1.7 parts of boil ing water. It even exceeds nitrate of potash as an oxidizing agent; and if combustible substances, such as carbon, sulphur, or phosphorus be heated, or forcibly rubbed with it, a detonation or explosion occurs. This salt is employed in the manufacture of lucifer matches, iu certain operations in calico-printing, and for filling the friction-tubes employed for firing cannon, the best mixture for these tubes consisting of 2 parts of this salt, 2 of sulphide of antimony, and 1 of powdered glass. A mixture known as white gunpowder, consisting of chlorate of potash, dried ferro-cyanide of potassium, and sugar, has been employed for blasting purposes; but its preparation is accompanied by so much danger that it is seldom used. This salt does not occur as a natural product, but may be obtained by passing a current of chlorine gas through a hot solution of caustic potash; 6 eq. of chlorine combining with 6 eq. of potash to form 5 eq. of chloride of potassium, and 1 eq. of chlorate of potash, according to the equation: 6C1 + 6 (KO,H0) = 51K1 } 6H0. The two salts are easily separated by crystallization, as the chlorate is comparatively insoluble, and the chloride extremely soluble. gypochlorite of potash (KO,C10) can only be obtained in solution. tinder the title of eau de Jarelle, it is sold as a bleaching agent. It is obtained by passing chlorine gas through a cold dilute solution of carbonate of potash, when chloride of potassium and hypochlorite of potash are formed, from which the chloride may he removed by crystallization. The phosphates of potash, formed by the different varieties of phosphoric acid, are sufficiently noticed in the articles PHOSPHATES (in physiology) and PHOSPHORUS. The silicates of potash arc important compounds in connection with the manufacture of -glass; they also enter into the composition of Fuel's water-glass, or soluble glass, and have been employed by Ran some and others as a coating by which the decay of magnesian and other limestones may be prevented. The chromate and trichromate of potash are sufficiently noticed in the arti cle CHROMIUM. The baloid salts of potassium may be passed over very briefly. The chloride of potassium (KCl) is obtained in large quantity in the preparation of chlorate of potash, or may be procured by burning potassium in chlorine gas, when the result of the brilliant combustion which takes place is this salt. In its general characters, it closely resembles common salt (NaCI), except that the former communicates a violet, and the latter a yellow tint to the flame of alcohol. It is a constituent of sea-water, of salt.
marshes, and of many animal and vegetable fluids and tissues. The bromide and iodide of potassium are sufficiently noticed in the articles Brun= and ImanzE. Fluoride of potas sium (KR) possesses the property of corroding glass. There are no less than five sul phides of potassium, commencing with the'photo-sulphide (KS), and terminating with the penta-sulphide (KS5). The latter is the main ingredient in the hepar sulphuris, or liver rf sulphur, used in medicine. It is a brown substance, obtained by fusing, at a tempera ture not exceeding 482', 3 eq. of potash and 12 eq. of sulphur, the compounds being 2 eq. of penta-sulphide of potassium and 1 eq. of hyposulphite of potash From this mixture, the penta-sulphide may be removed by alcohol, in which it dissolves. The yellow and the red p'russiate (or the ferro-cyanide and ferrid-cyanide) of potash are noticed in the articles FERRO-CYANOGEN and FERRID-CTANOGEN. The cyanide of potassium (KCy) may be procured by heating potassium in cyauogen gas, when brill iant combustion occurs, and the resulting product is this salt. It may, however. be more cheaply and easily prepared by Liebig's process, which does not, however, yield it pure, but mixed with cyanate of potash—an impurity which is of no consequence for most of the applications of cyanide of potassium, as, for example, electroplating and gilding. Eight parts of anhydrous ferro-cyanide of potassium are mixed with three parts of dry carbonate of potash; the mixture is thrown into a red-hot earthen crucible, and kept in fusion till carbonic acid gas ceases to be developed, and the fluid portion of the mass becomes colorless. After a few moments' rest, the clear fused salt is decanted from the heavy black sediment, which consists chiefly of metallic iron in a state of minute division. It has recently been derived from an unexpected source. In some of the iron furnaces where raw coal is used for fuel in the hot-blast, a saline-looking sub stance is sometimes observed to issue in a fused state from the tweer-holes of the fur nace, and to concrete on the outside. Dr. Clark of Aberdeen has shown that this substance is mainly cyanide of potassium. This salt forms colorless deliquescent crys tals, very soluble in water. It exhales an odor of hydrocyanic acid, and is said to be as poisonous as that acid. Its great deoxidizing power at a high temperature renders it a valuable agent in many of the finer operations of metallurgy.