GLYCERIN, or GLYCERINE, a triatomic alcohol of the fatty series, or CH2 (OH•) •CH (OH) •CH2 (OH). Glycerin was discovered in 1778 by Scheele, who obtained it in the prep aration of lead plaster by saponifying lard with oxides of lead. Glycerin occurs in most natural animal and vegetable fats in combination with fatty acids, from which it can be obtained by saponi fying with alkalies. It is also formed during the alcoholic fermentation of sugar. Pure glycerin is obtained by heat ing neutral fats in a still, with a con densing apparatus, and passing steam in small jets through the melted fat, the temperature being kept below 600° F., and above 550° F.; the fat acids separate out in the receivers from the glycerin and water; the glycerin is then concen trated by evaporation. Glycerin is a thick, colorless, inodorous, neutral syrup, which has a very sweet taste; it mixes with water in all proportions, is soluble in alcohol and in chloroform, but insolu ble in ether. Glycerin distilled with
phosphorous pentachloride, yields acrolein. By the action of a mixture of equal parts of concentrated nitric acid and sulphuric acid, it is converted into NITROGLYCERIN, CH2-0 • ( NO2. ) • CH • 0 (NO2) •CH2•0 (NO2) (q. v.). Glycerin is used for preserving fruits, also as a solvent for various salts, and it prepar ing copying-ink; also as a lubricator for machinery and clockwork, and is placed over water in gas meters to prevent freezing, and is used for filling floating compasses. It is employed in the form of nitroglycerin in the preparation of dynamite, and for mixing with soap to form glycerin soap, which tends to soften the skin.
Glycerin is used on account of its physi cal properties as an adjunct to lotions in skin diseases to prevent the surface be coming dry. It can be used as a sub stitute for sugar in the diet of diabetic patients.