A Manual of the Chemistry of the Carbon Compounds

U THE CHEMISTRY OF
exist in two modifications, one turning the polarized ray to the right,
and the other to the left. In such a case the heraihedral faces are
differently arranged, and when the two kinds of crystals are placed iu
the same position it will be found that the hemihedral faces appear
in one crystal on the right, and iu the other on the left side, or one of
the crystals looks like the image of the other in a mirror. These
bodies are not only optically active in the solid state, but also in
solution; and there exist also many liquids having this property, as
for instance, amyl alcohol, oil of turpentine, &c.
This optical property has been made use of in the arts; it is used
to determine the quantity of sugar contained in syrups. Under the
head of caDe-sugar it will be explained how, by simply measuring the
angle of deviation, the quantity of sugar contained in. a liquid can he
ascertained.
Colour of th Carbon Compounds.—Most carbon compounds are
colourless, when in the pure state; but there exist also a great number
having characteristic colours, and many of these are used as dye stuffs
or for the preparation of pigments, such as indigo, the colours of
madder-root, cochineal, aniline colours, &c. It appears that the colour
of these bodies depends on their chemical constitution; they contain
certain elements, as oxygen and nitrogen, combined in a peculiar
manner, as we shall see when we come to the study of these bodies.
Odour end Tmte.—~The odours of volatile carbon compounds vary
very much, as the following examples show: spirits of wine, ether, acetic
ether, acetic acid, chloroform, camphor, oil of cloves, &c. Compounds
having a similar constitution often possess a similar smell. Thus the
marsh-gas hydrocarbons all possess a.faint smell of flowers, which is
more or less perceptible according to the volatility of the body. The
compound ethers of the fatty acids smell like various kinds of fruit,
and are on that account used by confectioners and perfumers. Most
sulphur compounds, in which this element is not combined with oxygen,
are characterized by their disagreeable odour, and many chlorides
have a smell similnr to that of chloroform.
Delations between odour and chemical constitution certainly exist j
but only a few such are known. Thus the amines or compound
ammonias have an odour resembling that of ammonia, and many
aldehydes, compounds which readily absorb oxygen from, the air,
possess a peculiar suffbeatiug smell.
The taste of carbon compounds is equally as varying as their
odour; we find here also that analogous constitution produces a
similar taste. The alkaloids, as quinine, strychnine, &c, have an
intensely bitter taste, whilst the taste of the alcohols of polygenic
radicals, as glycerin, mannite, and sugar, is pleasantly sweet,
Solubility.—A. great number of carbon compouuds are soluble in
water, others only in alcohol, ether, acetic acid, benzene, &c. These
different solvents arc made use of in separating OT purifying them.
In homologous series the first members are generally more soluble in
water than the higher ones. Thus in the seiies of the alcohols and