A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS. 137
The so-called pyroligneous acid, obtained by the distillation of
wood, is dilute acetic acid mixed with empyreumatic substances. It
is used to prepare the common commercial acetic acid, by neutralizing
it with lime, and evaporating the solution to dryness; the residue is
gently roasted so as to destroy the foreign matters, and then distilled
with hydrochloric acid.
. To obtain pure acetic acid, five parts of anhydrous fused sodium
acetate are distilled with six parts of pure conoentrated sulphuric
add. It is a colourless liquid, boiling at 118°, and solidifying on
cooling into large transparent plates (glacial acetic acid) melting
at + 1.7°. It possesses a pungent and sour smell, and is corrosive,
destroying the skin. It mixes with water in all proportions, and is
a solvent for essential oils, hydrocarbons, and many other bodies
which are insoluble in water. At 15° it has the spec. grav. 1-0553.
On mixing with water a contraction first takes place until £0—23
per cent, of water are present; this acid has the specific gravity
1*0748. On further addition of water the specific gravity diminishes
again; acetic acid of 43 per cent, having the same specific gravity
as the anhydrous acid.
p IT Q\
Potassium Acetate 4 V f O * 8 obtained by neutralizing dilute
acetic acid with purified potassium carbonate. It is a very deliquescent
salt, and difficult to crystallize The dry salt fuses at 309°,
and may be heated even stronger without undergoing decomposition.
On cooling it solidifies to a radiated crystalline mass. If it is dissolved
in common strong acetic acid, and the solution heated, water is
given off, and a compound C » Hs °-\o + G &Q \ Q (8O 0^1^ biacetate
of potash) formed, which on heating to 200° splits up into anhydrous
acetic acid and potassium acetate. This reaction may be nsed for
preparing pure acetic acid.
Sodium Acetate is obtained on the large scale by dissolving the
roasted crude calcium acetate in water, and decomposing it by sodium
sulphate. The filtrate yields on evaporation sodium acetate, which
if strongly heated may be freed from all traces of empyreumatio
substances still adhering to it. Sodium acetate crystallizes in long
monoclinic prisms ^A >O + 31^0, which melt on heating, and
give off water. The anhydrous salt, fuses above 300° to a colourless
dear liquid.
Ammonium Acetate vffx rO.—The anhydrous salt is formed by
passing dry ammonia into pure acetic acid. It is very soluble in
water. On heating it decomposes into water and acetamide
CAONH
Aluminium. Acetate is prepared by adding a solution of lead acetate
to a solution of aluminium sulphate; it is used under the name of
"red liquor," as a mordant in calico-printing.