Anthracene

Anthracene, $(C\_6H\_4)\_2(CH)\_2$, is a substance obtained in the distillation of coal-tar. Although long known to chemists, it is as the source of artificial Alizarin (q.v.) that it has become of commercial value. By a process of oxidation with bichromate of potash, it is changed into anthraquinone, which in turn is treated first with sulphuric acid and then with potash, the alizarin being separated by the addition of hydrochloric acid. Conversely, anthracene is readily obtained from alizarin by heating that substance with zinc dust—a mixture of metallic zinc with oxide and hydrate of zinc—when, by the absorption of hydrogen, anthracene is formed. When perfectly pure, it forms white pearly scales, melting at about 410° F. (210° C.), and at a higher temperature distilling without decomposition. It is insoluble in water, but readily dissolves in boiling alcohol, ether, or turpentine. When viewed by a ray of sunlight, it exhibits a fine blue fluorescence, if pure. The commercial article, dissolved in benzene, gives a green fluorescence. By prolonged exposure to light, it is changed into an isomeric body, paranthracene, which again on fusion yields anthracene. Anthracene gives rise to a large number of compounds, formed by replacing part of the hydrogen which it contains with chlorine, alcohol radicals, &c., and accordingly named chloranthracene, methyl-anthracene, and so on.