A Manual of the Chemistry of the Carbon Compounds

302 THE OHEMI8T&Y OF
to the right, Its chemical properties are very similar to those of
turpentine oil; it yields a solid hydrate, and crystalline hydrochloridea.
With bromine and aniline it forms cymene. Similar terpenes exist
in the oils of orange-peel, bergamot, &c.
TEGPENES FROM OTHKR SOUKCES,
These hydrocarbons are found in a great number of volatile oils,
some of them consisting only of terpens, such as oils of lavender, juniper,
copaiba, cubebs, pepper, elemi, and the camphor-trees. Others are
mixtures of terpenes with acids, as oil of valerian; or with aldehydes,
as oil of chamomile, which contains angelicaldehyde, A great
number of essential oils also contain, besides, terpenes, camphors,
cymene, or other aromatic compounds.
CAOUTCHOUC AND GUTTA-PJ3BCHA,
Caoutchouc or IndAa^tvXAev is the dried milky juice of several
tropical trees (Ficuselastica, Jatropha elastica, Sijphonia Cahuchu,SK.).
The fresh juice has an acid reaction; on mixing it with water,
caoutchouc separates gradually out as a white- curdy precipitate,
whioh dries up to a gum-like mass. The black colour of the commercial
article is due to the effect of smoke; it may be purified by
dissolving it in chloroform, and precipitating the clear solution with
Bpirits of wine. It consists olnefly of a mixture of hydrooarbous,
polymeric with the terpenes. It is insoluble in water and alcohol;
with ether or petroleum it forms a gelatinous mass, and partially
dissolves. It is completely soluble in oil of turpentine, benzene,
chloroform, and carbon disulphide. When cold it is hard and tough;
on heating it becomes soft and elastic; and at a temperature above
the boiling-point of water it melts, but on cooling does not return to
the original state, but remains soft and viscid.
It is much used for the manufacture of waterproof and elastic
fabrics, for elastic tubing, &c., and is a most valuable substance for
the chemists, as it is only affected by a very few chemical agents.
Caoutchouc combines in different proportions with sulphur. The
so-called vulcanized India-rubber, whioh is much more elastic than
common caoutchouc, is obtained by mixing the latter intimately
with sulphur by means of carbon disulphide; it contains about 2
to 3 per cent, of sulphur. By mixing it with about half its weight
of sulphur, it is converted into a hard, horny mass, called "Ebonite "
or "Vulcanite," which is much used for making combs, disks for
eleotrio machines, &o.
By destructive distillation, caoutchouc yifelda a» oily liquid, con-