Distillation

(-til-lā'shun.) [From L. dis, apart, and stillo, I trickle.) (Chem.) An operation by which a liquid is converted into vapor by heat, which vapor is condensed by cold in a separate ve el. It maybe employed for various purposes: thus simple D. purifies liquids; it enables a more volatile to be separated from ale volatile substance; by its means a liquid po e ing a definite boiling-point may be separated from other liquids po e ing other boiling-points. This latter is known as fractional D., and is much used in the separation of hydrocarbons, the various products being collected at intervals of, say ten degrees of temperature. The e ential parts of a distilling apparatus are a ve el in which the substance is heated, called sometimes a still and sometimes a retort; a condenser or refrigerator, in which the vapor is cooled, and a receiver in which the condensed products are collected. A very convenient form of apparatus for D. of water and other liFig. 270.-DISTILLATION.-LIEBIG'S CONDENSER. quids is shown in Fig. 270. A is a stoppered retort, the neck of which fits into the tube of a Liebig's condenser (B), which consists of a gla tube (C) fitted by means of corks into a gla , copper, or tin tube (D), into which a stream of cold water is pa ed by the funnel E, the heated water running out through the upper tube F. The water furnished by the condensation of the steam pa es through the quilled receiver G, into the flask H. Heat is gradually applied to the retort by a ring gas burner. D. was an important operation in the earliest alchemical proce es of which we have any record; it does not, however, appear to have been known before the time of Pliny. See DESTRUCTIVE DISTILLATION. Distilled Waters, (-tild.) (Chem.) They are obtained by distilling water along with the parts of plants containing e ential oils. Rose-water is a familiar example. [s. 293]