450 THE CHBMISTEY OF ESSENTIAL OILS
of carbon dioxide-free water, being neutralised by means of semi-normal
sulphuric acid. This titration gives the figure from which the ester per-
centage is calculated.
A few drops of semi-normal alcoholic potash are added, and the
liquid allowed to evaporate on the steam-bath.
To the residue is added 10 c.c. of dilute phosphoric acid, prepared by
mixing about 3*5 c.c. of 88 per cent, acid with 100 c.c. of carbon dioxide-
free distilled water.
The carbon dioxide flask is now immediately attached to the appara-
tus, and the distillation is commenced.
It should here be noted that the distilled water in the steam generat-
ing flask must have been allowed to become entirely free from carbon
dioxide by at least half an hour's preliminary boiling.
The whole apparatus must be thoroughly cleansed and freed from air
by allowing steam from the generator to blow through for a few minutes
before attaching the carbon dioxide flask.
Distillation is allowed to proceed, the water in the generator being
kept boiling as quickly as possible, and the volume of liquid in the
smaller flask being kept at about 10 c.c. by means of a small flame.
The time taken for the collection of the required 250 c.c. of distillate
is usually about thirty minutes.
The distillate is collected in a 500 c.c. Erlenmeyer flask having a
mark upon it to indicate the level of 250 c.c. Phenolphthalein solution
and a sufficient excess of deci-normal sodium hydroxide solution are added
to the distillate and the excess of alkali determined by back-titration.
Bergamot oil contains as its principal constituent linalyl acetate, to
the extent of up to over 40 per cent. It contains limonene, pinene,
camphene, bornylene, bisabolene, Z-linalol in the free state, dihydrocumic
alcohol, nerol, terpineol, and about 4 to 5 per cent, of the solid body
bergaptene, C 12 H 8 O 4. \
OIL OF SHADDOCK.The shaddock is the fruit of Citrus decumana, usually known in this
country as the grape fruit. It is a large fruit, native to China and Japan,
and introduced into the West Indies by Captain Shaddock, whence its
name. The oil, which is not known to any extent in commerce, has a
specific gravity of about *860 and an optical rotation of + 90° to + 95°.
It is a typical Citrus oil, containing much limonene, but its constituents
have not yet been carefully examined.
According to Brooks, the le ives of the tree Citrus decumana growing
in the Philippines, which is probably a variety of the European tree,
yields 1*7 per cent, of an oil having the following characters:—Specific gravity at —6 0*870-870
Optical rotation at 30° + 22-9°
Refractive index at 30° 1-4644
Ester number 10
It contains dipentene, 15 per cent, of linalol, and 1 per cent, of citral.
H. F. Zoller* has examined the oil obtained by steam distillation
from the peel of Citrus decumana grown in the United States. He
found it to have the following characters :—
1
Jour. Ind. Eng. Clwm. (1918), 10, 5, 364.