Chemistry of Essential Oils

308 THE CHEMISTEY OF ESSENTIAL OILS

According to Walbaum, the oil contains about 50 per cent, of linalol,.

but his results were obtained by a direct acetylation. If the method of

Boulez be used, which is necessary in the case of linalol, from 65 to 70

per cent, of linalol is indicated. Dextro-a-pineue, i-a-pinene, /2-pinene,

dipentene, cymene, terpinene, ger-aniol, borneol, acetic esters, and decyl

aldehyde are also present in the oil, with, possibly, phellandrene and

terpinolene.

OIL OP DILL.

Dill OH, is obtained by the distillation of the fruit of Anethum grav-
eolens Linnasus (Peticedanum graveolens Bentham). It is indigenous,
to Central and Southern Europe, but is found in many other localities,
such as the Caucasus, Persia, and the north-east of Africa and India.
Slight botanical differences exist between the European plant and that
grown in India, so that the latter has been described as a distinct
species (Anethum Sowa). A difference of opinion exists as to whether
this distinction is justifiable, but the oils obtained from the two plants
are certainly not identical. The yield of oil obtained from the seeds is
about 3 to 4 per cent.
European dill oil is a pale yellow liquid having the following char-
acters :—
Specific gravity... 0*895 to 0'918 (rarely below 0-903)
Optical rotation.. + 70° to + 82°
Refractive index.. 1-4830 „ 1-4900
Carvone.... 30 to 60 per cent, (by the sulphite method)
The oil is soluble in from 4 to 9 volumes of 80 per cent, alcohol.
In spite of the difference in odour between this and caraway oils,
the composition of the two is almost identical, both consisting nearly
entirely of limonene and carvone. Dill oil, however, contains less car-
vone than caraway oil. Hence the tests given under caraway oil apply
here, and stress should be laid on the specific gravity, optical rotation,
and fractionation. Not more than 15 per cent, should distil below 185°,
and not less than 40 per cent, above 220°. English distilled oils usually
have the highest specific gravity, from "910 to -916, and are conse-
quently held in the highest esteem. The following are the average
fractions obtained from English and German oils :—

Below 185°

185° to 200°

200° „ 220C

220° „ 230°

Above 230°.

East Indian dill has a much higher specific gravity than European

oil, this figure usually varying from -945 to *970. Its rotation is from

+ 40° to + 50°. This high specific gravity is in all probability due to

the presence of dill apiol, a body isomeric with ordinary parsley apiol,.

discovered by Ciamician and Silber. Indian oil contains much less

carvone than European oil, as does the Japanese oil, which also pos-

sesses a high specific gravity and appears to be nearly identical with

Indian oil. A sample of Japanese oil examined by Umney was found

to have a specific gravity 0'964 and optical rotation + 50° 30'. The

optical rotation of both varies from + 40° to + 50°. Spanish oil is.

English.

10 per cent.

20

20

48

2

German.

10 per cent.

22

22

42

4