306 THE CHEMISTKY OF ESSENTIAL OILS
the market to be disposed of. A portion of the carvone is abstracted by
fractional distillation, and the misleading name "rectified caraway oil "
often given to the remaining oil, which frequently has a specific gravity
of 890 to '900 and a correspondingly high rotation. When all the car-
vone is abstracted the resulting " carvene " as it is called—in reality
almost pure limonene, with traces of carvone—is sold as " light" oil of
caraway. It is used for perfuming cheap soaps, but it is false economy,
as the same value in pure oil or in carvone has a far higher odour value,
and is cheaper in the end. " Carvene " is comparable to " citrene," the
waste terpenes obtained in preparing terpeneless oil of lemons, and
" auranciene," the corresponding terpenes from orange oil. They are
all practically useless for perfumery purposes, and are either sold under
misleading names or used to adulterate the respective oils from which
they have been obtained. There is also an oil known as caraway chaff
oil, which appears to be distilled from a mixture of the herb itself, and
the chaff obtained on threshing the seeds. "Light" caraway oil ex-
amined by the author had a specific gravity 848 and an optical rotation
- 103°. Umney gives a sample of "light" caraway or "chaff" oil as
having a specific gravity 8482 and an optical rotation of - 585°. At-
tempting to determine the question as to when the carvone was formed
in the plant, Schimmel & Co. distilled the samples described below,
grown by them on their Miltitz fields:—
No. 1 from fresh long-cut, blooming plants with partly ripening
fruits.
No. 2 from fresh plants cut at the same time and in the same way,
from which, however, the umbels bearing both flowers and ripening
fruits had been removed, so that the stalks and the leaves alone were
distilled.
No. 3 from plants in a more advanced stage of ripening, and after
the time of blooming, but before the full ripening of the fruits.
The following were the physical constants of the oils obtained :—
Specific Gravity. Refractive Index. Optical Rotation.
Uo. 1 0-882 1-48306 + 65° 12'
.,, 2 about 0-880 1-5083 + 20° 36'
,, 3 0-9154 1-48825 + 63° 6'
The odour of oil No. 2 hardly resembled that of caraway seeds, nor
did it contain either limonene or carvone, the characteristic constituents
of caraway oil, in any perceptible quantity. The small sample was just
sufficient for ascertaining the boiling-point; it began to boil at 195° C.,
the thermometer then rapidly rose to 230° C., and between 230° and 270°
about 65 to 70 per cent, distilled over; the residue was resinified.
Sample No. 1 evidently contained much more terpene and less
carvone than sample No. 3. Hence it is possible that the latter results
from the oxidation of the former during the ripening of the plant. A
body of high boiling-point, not yet identified, was detected in small
quantity in each of these oils\
The constituents recognised in caraway oil are carvone, d-limonene,
dihydrocarvone, carveol, and dihydrocarveol, and a base having a
narcotic odour which has not been investigated.
OIL OF CORIANDER.This oil is distilled from the fruit of Coriandriim sativuni, a native
of the Levant and Southern Europe, cultivated in many places all over