A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS. 271
Oldk Acid or Elaio Add C.9H¥Oa exists as triolein, the fluid constituent
of many fats aiid oils, m the fat of tlie pig and goose, iu
olive-oil, oil of almonds, &c. To prepare the acid the oils are
.saponified with lead oxide, and the lead salts exhausted with ether,
which dissolves only lead oleate, The ethereal solution is shaken
with hydrochloric acid, the upper layer removed, and the ether removed
by distillation. The impure oleic acid left behind is dissolved in
ammonia, and barium chloride is added, which precipitates barium
oleate. After purifying thia salt by crystallization from alcohol, it is
decomposed in a closed vessel with tartaric acid, and the pure oleic
acid thus obtained is dried in a current of carbon dioxide, in order to
prevent oxidatiou. Large quantities of impure olefc acid are now
obtained as a by-product in tHe manufacture of stearin-candles. If
this crude acid does not contain a large quantity of oxidation-products,
it may be purified by cooling it down to — 7°, and subjecting the
crystals which separate out to strong pressure. The residue is again
melted and cooled down, and well pressed, and this operation repeated
if necessary. Thus a pure acid is obtained, which may be recrysfcallized
from alcohol.
Pure olefc acid is a colourless oil solidifying at alow temperature to
crystals melting at 14°. "From alcohol it crystallizes in brilliant white
needles. The perfectly pure acid remains unaltered in the air, but in
an impure state it rapidly absoi^bs oxygen, assuming a yellow colour
and rancid smell, and losing the property to crystallize. It volatilizes
with ovetheated steam or in vacuo, without decomposition; but
under the ordinary atmospheric pressure it is decomposed on heating,
yielding fatty acids, such as acetic acid and caprylic acid, and a large
quantity of sebacic acid. When it is heated with caustic potasli, it is
resolved into acetic acid and palmitic acid.
By passing nitric trioxide into cold oleic acid it is converted into
the isouieric datdic acid, a solid mass, crystallizing from an alcoholic
solution in sinning scales, melting at 45°. It is stable in the air, and
can be volatilized without decomposition, Trioleiu is also converted
by nitric trioxide into solid triclatdiih If, therefore, this gas be
passed Into oil of olives or almonds, they solidify to ft crystalline
IUOSB. We are not yet able to explain the singular action of nikous
trioxide upon oleic acid and other acids of this series.
. Olrfc and elaiidic acids unite with one molecule of bromine. OMc
dibramide is a heavy, thick yellow oil; by treating it with a cold
alcoholic potash solution, monobromoleie and CjgH^BrOj, a crystalline
substance, is obtaiued, which by the action of nascent hydrogen is
again converted into oleic acid.
By the action of a hot alcoholic potash-solution on monobromoleic
acid or on the dibrouride all the bromine is taken out, and stearolie
twid C,8HS)jOs is formed, which crystallizes in silky needles melting at
48", aud volatilizing on heating without decomposition It unites
with one or two molecules of brotu'sue; fuming nitric acid oxidizes
if to siemw->tl>r ariif,nti'fnfc arid and azefatr nldebitdr.