A Manual of the Chemistry of the Carbon Compounds

108 THE CHEMI8THY OF
—100° it becomes viscid, but does not solidify. Its specific gravity
at 0° is 0-80625, and at 15° 079367. Ethyl alcohol is very inflammable,
and burns with a blue, non-luminous flame. It absorbs moisture
with great avidity, and is miscible with water iu all proportions, the
mixture evolving heat and undergoing contraction. The greatest contraction
takes place when forty-six parts by weight of alcohol or one
molecule are mixed with fifty-four parts or three molecules of water.
Alcohol is a solvent for resins, fats, essential oils, and many other
bodies which are insoluble in water. Many salts and also gases
dissolve in it too, some of them being even more soluble in it than
in water.
As the value of spirits of wine depends on the quantify of alcohol
contained in it, it is of great importance to have a rapid and exact
method for ascertaining its strength. When the spirit only contains
water, the amount of alcohol is easily obtained by ascertaining the
specific gravity of the liquid by means of a delicate hydrometer, and
subsequent reference to accurate tables, showing the percentage of
alcohol. When the liquid to be tested contains sugar or other nonvolatile
substances, as those found in wine and beer, one-third of a
measured quantity of the liquid is distilled off, all the alcohol coming
over with the first portion. The distillate is then diluted with water
up to the original volume, and examined with the hydrometer. In
these determinations the temperature must be observed, and corrections
for deviations be made, when the temperature differs from that
at which the instrument has been graduated, from the fact that
alcohol expands considerably with an increase of temperature.
The " proof spirit" of the excise contains 50*8 per cent, by weight
of alcohol, and has at 15'-5 (60° F.) the specific gravity 0'92O. Owing
to the high duty on pure spirit the Government allow the sale of a
mixture of ninety parts of strong spirit, and ten parts of crude wood
spirit, called "methylated spirit," for manufacturing and scientific
purposes.
The quantities of alcohol in different spirituous liquors vary very
much. Brandy, whisky, &c, contain 40—50 per cent.; wines from
17 per cent. (Madeira, port]) to 7—8 per cent, (light claret and hock);
whilst ale and porter contain 6—8 per cent., and German beer about
4 per cent.
The least trace of alcohol in an aqueous solution can be readily
detected by adding to the liquid a little benzoyl chloride, which is
only slowly acted upon by water, but forms with alcohol at once ethyl
benzoate, a liquid having a very characteristic aromatic odour, and
which will be readily perceived after the excess of the chloride has
been destroyed by caustic potash. By means of this reaction the
presence of 0*1 per cent, of alcohol in a few cb.cm. of water can be
shown,
Sodium Mlvyhte \& \ O.—Sodium dissolves in absolute alcohol
with the evolution of hydrogen; on cooliug colourless crystals separate,