The esters in the oil, being combinations of alcohols and acids, serve
as a basis for the identification of the acids in combination. In order
to accomplish a separation of the combined acids a small quantity of
the oil was saponified with alcoholic potassium hydroxid by heating on
a water bath for half an hour. After dilution of the mixture with water
and separation of the oil the alkaline liquid, which contained a small
amount of the oil held in suspension, was shaken out with ether. The
liquid was then acidified with sulphuric acid and distilled with steam.
The oily globules which separated on the distillate were extracted with
ether and the solvent evaporated. A small amount of an oily liquid
with very offensive odor remained. This mixture of oily acids was
neutralized with sodium hydrate and precipitated with a dilute solution
of silver nitrate. Two fractions resulted:
Fraction 1. 0.0430 gram silver salt gave 0.0160 gram silver = 37.2
per cent silver.
Fraction 2. 0.0440 gram silver salt gave 0.0197 gram silver = 44.7
per cent silver.
From the results obtained it is evident that the fractions consist of
the silver salt of undecylic acid, which requires theoretically 36.8
per cent of silver, and silver salt of heptoic (œnanthylic) acid, which
requires 45.5 per cent of silver.
The aqueous distillate from the above, after being made neutral with
sodium carbonate, was evaporated to small volume and precipitated in
three fractions with silver nitrate:
Fraction 1. 0.243 gram silver salt gave 0.1837 gram silver = 75 per
cent silver.
Fraction 2. 0.3255 gram silver salt gave 0.2370 gram silver = 72.9
per cent silver.
Fraction 3. 0.3492 gram silver salt gave 0.1840 gram silver = 52.9
per cent silver.
The greater portion of the soluble combined acids consisted of
valerianic acid, the silver salt requiring 51.6 per cent of silver. A
trace of formic acid was also indicated in combination as an ester in
fraction 2, above.
The chief acids in combination as esters in the oil appear to be
œnanthylic (heptoic) and valerianic, the former being preponderant.
Formic and undecylic acids occur only as traces. All of the above are
no doubt combined in the oil as esters of borneol.