EUTACB^E 451
1. 2.
Specific gravity 0 845 0'860
Refractive index 1-4750 1-4785
Optical rotation + 72-5° + 78-5°
The constituents present, with their approximate quantities, are as
follows:—
a-pinene.0-5 to 1-5 per cent.
d-limonene 90 „ 92 ,,
Linalol 1 „ 2 „
Citral 3 „ 5
Geraniol......... 1 ,, 2 ,,
Geranyl acetate, linalyl acetate, and citronellal are probably present
in traces.
OIL OF CITRON.This oil is expressed from the fresh peel of the fruit of Citrus medica
var. vulgaris, the ordinary citron, a native of the Himalayas, which was
cultivated by the Aryans from very early times. In France the fruit is
known as a " cedrat"—the French " citron " being our lemon. Conse-
quently " essence de citrons " must not be confused with citron oil. The
tree flourishes in the south of Europe, particularly in Italy, the fruit
sometimes weighing from 10 to 14 Ib. Several other varieties of this
plant exist and appear to be used for expression, when the figures given
below will be exceeded; for example, some varieties yield an oil with a
specific gravity of about 0870 and optical rotation about + 67°. This
oil, which is seldom met with pure, should have the following constants:
specific gravity 851 to 854, rotation + 77° to 82°, refractive index about
14750. It contains chiefly limonene, dipentene, citral, and a crystalline
body ; melting-point 145°. The usual adulterants are lemon and orange
oils and their terpenes. The odour of this oil is very little superior to
that of good lemon oil, whereas the price demanded does not justify its
extensive use in commerce.
OILS OF XANTHOXYLUM.Thorns, about two years ago, reported on the essential oil of the fruit
of Japanese pepper, Xanthoxylum piperitum, which yielded 433 per
cent, of the oil. Schimmel & Co. have stated that the chief constituent
of the oil is citral. The oil has now been more exhaustively examined by
Duruttis.^1 He finds the oil to have the following characters:—
Specific gravity at 20° 0-890
Optical rotation - 26-5°
Kefractive index 1-4732
From the fraction 175° to 177° (specific gravity = 0-8469, optica
rotation = + 557°) a tetrabromide melting at 120° and a nitrosochloride
melting at 93° to 95° were obtained. This fraction appears to be a mix-
ture of dipentene and dextro-limoneue. The oil consists of terpenes to
the extent of about 90 per cent. The fractions boiling over 180° were
treated with sodium bisulphite, and the compound formed treated in the
usual manner, when a body was liberated which was found to be cumic
aldehyde, which was identified by its forming a semi- carbazone melting
at 210°, and by oxidation to cuminic acid melting at 115°. In the fraction
1
Arbeit, a. d. Pharm. Inst. L'niv., Berlin, 60.