NAPIITHAVIC GROUP on SERIES. The starting point of the group is _Naphthalin a substance of great interest in the history of organic chemistry, from its being that upon which Laurent chiefly founded his theory of substitutions. It may be obtained in various ways, but is most easily and abundantly produced from the last por tions of the distillate of coal-tar whichbecome semi-solid on cooling. The liquid part of this mass is got rid of by pressure, and the naphthalin is then taken up by hot alcohol, from which it is obtained in a pure state by crystallization and sublimation.
Naphthalin crystallizes in large, thin, rhombic plates, which are unctuous to the touch, rind have a pearly luster. • Exposed to light under a glass covering, it gradually sublimes at an ordinary temperature in splendid crystals. It has a somewhat tar-like odor, and a pungent and somewhat aromatic taste. It fuses at 174°, and boils at 428°. Its specific gravity, in the solid state, is 1.15, and as a vapor, 4.528. It is not very inflammable, and when ignited, burns with a white smoky flame. It is insoluble in water, hut dissolves readily in alcohol, ether, and the fixed and essential oils.
By acting on naphthalin with au excess of sulphuric acid, we obtain sitipko-naphthalie acid (C 2 + 2Aq), from which, by substitution processes, a lace number of com pounds are produced. With nitric acid, naphthalin yields nitro-naphthalin binitro-naphthaliu and trinitro-naphthalin 0 2011,(N04),], the group ' or its multiples, substituted for one, two, an three equivalents of the hydrogen of the naphthalin. The final product of the prolonged action of boiling nitric acid on naphthalin is a mixture of oxalic and naphthalic or phthalic acid; the re-action being shown by the equation: This acid is also obtained by the continued action of nitric acid upon alizarin, which is an important fact, since it indicates a connection between naplithaliu and the coloring matter of madder.
Laurent has discovered a very numerous series of substitution compounds formed upon the type of naphthalin, into the composition of which chlorine enters. They are of little practical importance although their investigation has exerted a remarkable influ ence upon the progress of organic chemistry.