An´thracene

(C 14 H 10 ) occurs in coal-tar in small quantity, about 0.25-0.45 per cent. During the distillation of tar a high-boiling fraction, boiling above 270° C., is obtained; this is crude anthracene oil, a greenish oily substance which, on further distillation, yields a crystalline ma , 50 per cent anthracene. This is carefully purified by distillation and chemical treatment to separate the anthracene from the other substances occurring with it, and the product obtained is finally purified by crystallization. When pure it forms colourle crystalline scales melting at 216° C., and having a violet fluorescence. It forms a series of derivatives, the most important being anthraquinone and alizarine and the numerous derivatives of these. Anthracene was originally a usele product in coal-tar distillation, but it became valuable as soon as it was discovered that alizarine—from which many dyes are manufactured directly or indirectly—could be prepared from it.