280 THE CHEMISTEY OF ESSENTIAL OILS
with alcoholic solution of potash, the oil should give a result equivalent
to at least 98 per cent, of methyl salicylate. The salicylic acid result-
ing from the addition of acid to the saponification product, after a single
recrystallisation from alcohol, should melt at 155° to 157°. This will
guard against the use of impure salicylic acid in the preparation of the
artificial oil.
This oil is sometimes adulterated with petroleum or light camphor
oils, both quite easy of detection; also with sassafras oil, which, in spite
of its high specific gravity, is easily detected by its lowering the saponi-
fication number, and its characteristic odour remaining after the winter-
green odour has been destroyed by saponification. The oil is used to a
certain extent in pharmacy, either as a drug or to cover the nauseous
taste of other drugs, but more extensively as a flavouring in the manu-
facture of such confections as the American chewing gums.
Power and Kleberl have made an exhaustive examination of winter-
green and birch oils, and consider that they can be discriminated by
their odour, as would be indicated from the following results of their
work:—
In previous investigations the oils had been saponified by heating
with a solution of caustic alkali, and the alkaline solution subsequently
distilled, or shaken with a solution of either petroleum benzine or ether.
In order, however, that none of the constituents should become decom-
posed or altered by this treatment, they took advantage of the fact that
methyl salicylate combines with cold dilute solutions of the alkalies to
form salts of the ester. These are quite unstable, but the potassium
compound is readily soluble in water. The oils were, therefore, shaken
with successive portions of a cold dilute solution of potassium hydrate,
and when the oil had become reduced to about one-third of its original
volume an equal volume of ether was added, and the extraction with
alkali continued until nothing more was taken up by the latter from the
ether solution. After distilling off most of the ether, and the dissipation
of the last traces of the latter by heating for a short time on a water-
bath, the residues were weighed. The amounts were as follows:—
From 1500 grms. of Gaultheria oil, 15'7 grms. of residue, or 1-05 per cent.
„ 5000 „ Birch oil, ,. 9-8 „ „ 0-196 „
The portion of both oils which was soluble in alkali consisted of
pure methyl salicylate. The acid separated therefrom had a melting-
point of precisely 155
- 5° C., which is that of pure salicylic acid, and it
did not contain a trace of benzoic acid.
The ether residues formed at ordinary temperatures a semi-solid
mass, from which, by distillation with steam, a nearly colourless oil was
obtained which no longer solidified in the cold. The amount of this
was as follows :—
From Gaulfcheria oil, 6-3 grms. or CK2 per cent.
„ Birch oil, 2'9 ,, 0'058
From the residue remaining after distillation with steam there was
obtained a substance crystallising in colourless, odourless laminae, ot a
rly lustre, and having an apparently constant melting-point of 65*5°
C. The behaviour of this substance towards reagents proved quite con-
clusively that it is a paraffin, and most probably triacontane C 30 H 62.
Its analysis gave the following result:—
J
Schimmel's Report, October, 1895, 50.