A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS. 420
by passing nitrogen trioxide into its alcoholic solution. When pinewood
is steeped in an alcoholic solution of indol, containing hydro*
clJoric acid, the wood assumes a cherry-red colour, which scon
changes into a brownish-red.
NAPHTHALENE-GEOUP.
NAPHTHALENE C10H8.
This hydrocarbon is formed by the destructive distillation of many
carbon-compounds, a larger yield being obtained when the products
are exposed to a red heat. It is, therefore, found in quantity in coal
and wood-tar. But even substances which are comparatively rich in
hydrogen as alcohol, ether, acetic acid, &a, yield some naphthalene,
when their vapour is passed through a red-hot tube.
It occurs also in "Rangoon tar, or the petroleum from Burmah,
and has been produced synthetically by passing the vapour of phenylbutene
dibromide (page (402), through a red-hot tube:—
C^.C^Br, - C0H4.C«H4 + 2HBr + H2
Naphthalene is obtained from the portion of coal-tar boiling between
180° to 220° from which, on cooling, crude naphthalene crystallizes
out, which, is purified by pressing it to remove oily substances, and
then submitting it to sublimation or crystallization from alcohol.
Naphthalene crystallizes in large, transparent, brilliant plates,
melting at 80°, and possessing a faint, peculiar odour and a burning
taste. It boils at 217°, but sublimes readily at a much lower temperature.
On mixing hot alcoholic solutions of naphthalene and picric acid,
the compound C,nH8 + C,,H2(NO2)80H crystallizes on cooling in
golden-yellow needles, which are grouped in stars. This compound
is not decomposed by re-crystallization from alcohol or benaeue, but
ammonia resolves it into its constituents.
When naphthalene is boiled with dilute nitric acid, it is oxidized
to phthalic acid and oxalic acid.
In its chemical character, naphthalene bears a great resemblance to
benzene, and its constitution is best explained by the following
graphical formula s—
H H
A I
H Y Y V H
V Y
A k