192 THE CHEMISTEY OF ESSENTIAL OILS
Specific gravity
Optical rotation
Refractive index
Acid value
Ester „
,, „ (after acetylation)0-9659
- 39° 40'
1-5028
2-2
39-2
110-2
The oil contains a phenol of the formula C 9 H 12 O 2 ; a-pinene, lina-
lol, borneol, Z-terpineol, geraniol, methyl-eugenol, acetic, palmitic, and
other fatty acids, and a lactone of the formula C 1 4H 20 O 2.OIL OF SNAKE-KOOT (VIRGINIAN).
The roots of Aristolochia serpentaria, the North American serpentary,
or Virginian snake-root, yield from 1 to 2 per cent, of essential oil, having
the following characters :—
Specific gravity.. 0'960 to 0'990
Optical rotation..+ 20° , + 26°
Befractive index..1-4972 , 1-4980
Acid value.. 2 , 3
Ester „.65 , 80
„ „ (after acetylation).105 , 115
Borneol has been detscted as a constituent of this oil.
LABIATVE.OIL. OF LAVANDULA VERA (LAVENDER OIL).
This oil is obtained by distilling the flowers of Lavandula vera, the-
well-known lavender, a native of southern Europe. The plant is found
on the stony declivities of the Provengal Alps, the lower Alps of
Dauphine and Cevennes (and even so far north as latitude 46°), in
Piedmont, Switzerland, the mountains of Liguria and Etruria, and
various other places. Peculiarly enough, the plants come to their
greatest perfection and yield a much finer essential oil when transferred
from their native soil, and carefully cultivated in certain districts in
England, which produces the finest lavender oil in the world. The
principal lavender plantations in England are in the neighbourhoods of
Mitcham, Ampthill, Hitchin, and Canterbury.
Attempts have been made to establish plantations in Southern
France from young plants taken from parent stems in England; but
the plants quickly reverted to their original condition, and "English"
lavender oil can so far only be produced in England. For the details
of the methods of cultivation adopted, the reader is referred to the ex-
cellent monograph in Sawyer's Odorgraphia, vol. i. p. 361. A great
deal of the finest lavender oil is distilled with water over an open fire,
and, so long as care is taken that the plants themselves are not burnt>
the fine quality of the resulting oil largely justifies the process. Modern
distilleries, in which steam distillation replaces the old water distilla-
tion, give, however, a larger yield of oil, and, in general, these have
higher ester values than the water distilled oils. This point will be
referred to later. In England it is usual to allow the body of the still
in which the flowers are distilled to be very shallow as compared with
its width, in order to allow the oil to pass over rapidly and get away
from the source of heat, which might damage its odour. If a naked
fire be used, it is customary to suspend the charge of flowers in a
basket of sheet copper, with perforations all over it to allow the free