STEARIC ACID (from Gk. arlap, steer, tal low), One of the solid fatty acids. it exists as a glyceride (stearin) in most fats, and is especially abundant in the more solid kinds, such as mutton-suet. The stearic acid of com merce is in reality a mixture of stearie and palmitic acids. Pure stearic acid may readily he separated from this mixture by dissolving in hot alcohol and precipitating with a hot alcoholic solution of magnesium acetate, the precipitate being composed of practically pure sten rate of magnesium: in this reaction. one part. by weight, of magnesium acetate should be employed for every four parts of commercial stearic acid treated. The magnesium stertrate thus obtained is decomposed by hailing with hydrochloric arid, and the stearic acid set free is further purified by reerystallization from alcohol. Pure stearic acid is a colorless crystalline substance having neither taste nor odor; it melts at 69.2° 0. (157° F.). It is insoluble in water, on which it floats, but dissolves in alcohol and ether, its solution redden ing litmus powerfully. It may be distilled under
diminished pressure. The only stenrates soluble in water are the stearates of the alkalies, whose solutions are frothy and form a lather, but on the addition of an excess of water separate into an acid salt which is deposited in silky crystalline plates, and the free alkali, or more probably a basic salt, which remains in solution. (See Soar.) The stearates of the alkalies are soluble also in alcohol. Chloride of sodium (common salt ) has the property of separating the alkaline stearates from their aqueous solution.
Free stearic acid has been found in decom posing pus and in the cascous deposits of tuber culosis. In adipocere and in farces stearic acid occurs in the form of its calcium salt; in blood, chyle, and in serous fluids, in the form of sodium salts. See CANDLE; FATS; OILS; SOAP.