Retort

(from retorgueo, to bend back again.) In chemistry, a crooked matra , cons ducting the substance introduced into it, and sublimated or evaporated over the heat which it is exposed, into a recipient, into the neck of which its own neck is inserted, and if nece ary, luted. It is the most common and most useful instrument in distillation. Tt derives its name from its curved or twisted form. ‘The swell or most capacious part is called its belly; the upper part its arch or roof; and the bent part, which compared with the belly usually forms an angle of about sixty, its neck, which should be free and wide, but gradually diminish in diameter to the extremity of its neck or mouth. The belly of the retort is more usually round; though frequently oblong, and shaped like a cucurbit, These last are called English retorts, and are preferable in the distillation of substances that are apt to swell, and pa into the receiver anterior to decomposition. A ve el of this kind which has a little hole pierced in its roof is called a tubulated retort, This hole must be capable of being exactly closed with a stopple of proper materials. ‘Tubulated retorts are employed in distilling substances which it is nece ary to introduce after the receiver is joined on, as in operating for matine acid. Retorts employed in proce es for ga es have usually very long necks; for here no width of diameter is wanted for the condensation of vapours, and the narrowne of the neck allows but little admixture of the external air. Retorts are made of gla , earthenware, and sometimes of iron or silver: a leaden retort, moreover, is occasionally used, as m the proce for fluoric acid. 214