QUINOLINE, or LELCOLISE, An or ganic base to which many vegetable alkaloids are chemically more or less closely related. It may be obtained by the distillation of quinine, cinchonine, or similar substances, with caustic potash. It occurs, together with isoquinoline, a substance of the same molecular composition as quinoline, in coal-tar, and in bone-oil, and may be isolated in a somewhat impure state from the fraction distilled over between 236' and C. It is now prepared on a large scale by a purely artificial method, known as Skraup's method. This consists in heating 120 parts of glycerin with 100 parts of strong sulphuric acid, 38 parts of aniline, and 24 parts of nitro-benzene, a some what violent reaction soon setting in. After the reaction has subsided, the mixture is kept boiling for several hours, then cooled, diluted with water, and subjected to distillation in a current of steam until the portion of the nitro-benzene that has remained untransformed, is completely removed. The quinoline remains fixed in combination with sulphuric acid, but on adding an excess of soda and again distilling in a current of steam, it passes over almost pure: after drying, it may be further purified by fractional distillation. Three chemical transformations probably take place, in successive order, in this process: First, the action of sulphuric acid on glycerin causes the formation of acrolein, next, acrolein com bines with aniline, C,TI,NH,„ yielding acryl aniline, finally. by the oxi
dizing action of nitro-benzene, acry1-aniline loses hydrogen and is converted into quinoline, C1,11,\. Pure quinoline has a specific gravity 1.095 at C. and boils at C. Tt is scarcely soluble in water, but dissolves freely in alcohol and in ether. It is a tertiary aromatic base and com bines with acids to form crystallizable salts. The peculiar odor of quinoline is characteristic. Quin oline is largely used in the arts, especially in the manufacture of aniline colors. Tn medicine it is used as an antiseptic and as a substitute for quinine; it has also been found of great value in diphtheria. a weak alcoholic solution of quino line being applied to the diseased membranes.
The chemical constitution of quinoline is repre sented by the following graphic scheme: It may be seen that the molecule of quinoline is composed of two nuclei, the benzine nucleus and the pyridine nucleus. The substance qtanoline, mentioned above, has a much similar constitution and its chemical properties are much the same as those of quinoline itself; its boiling-point is, however, C., i.e. two degrees higher than that of quinoline: besides, at ordinary temperatures it is solid, its melting point being about 22' C.