KOSACE^E 407
traces of this body, and if kept in bottles that are not .quite full the
oxidation becomes more rapid, and crystals of benzoic acid are deposited.
This is more especially the case when the oil has been freed from prussic
acid. According to Schimmel & Co., 10 per cent, of alcohol added to
the oil retards this oxidation.
There appears to be little doubt that the action above indicated for
the decomposition of amygdalin does not take place as simply as in-
dicated. Recent researches by Kosenthaler
l
and others indicate that
the enzyme is not a single body but a mixture of ferments, and that the
system amygdalin-emulsin gives rise to the following series of reactions,
which end up with the oil containing benzaldehyde, hydrocyanic acid,,
and benzaldehyde-cyanhydrin:—
- Amygdalin, under the influence of amygdalase (one-of the fer-
ments), yields mandelonitrile glucoside and glucose. - Mandelonitrile glucoside, under the action of prunase (another
ferment), yields d0££ro-benzaldehyde-cyanhydrin and glucose. - Z>0#£ro-benzaldehyde-cyanhydrin is resolved by d-oxynitrilase into
benzaldehyde and hydrocyanic acid. - Benzaldehyde and hydrocyanic acid unite again, under the in-
fluence of rZ-nitrolese, to form rfe#£ro-benzaldehyde-cyanhydrin,.
and also unite, naturally, to form the inactive cyanhydrin. - rZ-oxynitrilase effects the resolution of the inactive cyanhydrin,
giving rise to laevo-benzaldehyde-cyanhydrin.
Bitter almond oil is a highly refractive liquid of powerful odour
having the following characters :—
Specific gravity 1-045 to 1-070
Optical rotation 0° to + 0° 10'
Refractive index 1-5320 to 1-5450
A higher specific gravity indicates a very high amount of hydrocyanic
acid, or an abnormal amount of benzaldehyde-cyanhydrin.
The oil is more soluble in water than almost any other essential oil,.
1 part dissolving in 300 parts of water at ordinary temperature.
Bitter almond oil, deprived of its prussic acid, has the following,
characters:—
Boiling-point 179°
Specific gravity 1-049 to 1-055
Optical rotation 0° to + 10'
Refractive index 1-5420 to 1-5460
The oil should not contain more than 1 per cent, of benzoic acid as
determined by titration with decinormal alkali: higher percentages in-
dicate that the oil is old or has been badly stored, and its odour and
perfume value are proportionally lower as the benzoic acid increases.
The constituents of the oil are, as above indicated, benzaldehyde, tc*
which the almond odour is due, hydrocyanic acid, and benzaldehyde-
cyanhydrin, C 6 H 5 CH(OH)CN, which, however, is easily decomposed into
its components by distillation with water, so that an oil which has been
deprived of its hydrocyanic acid directly after distillation may be practic-
ally free from benzaldehyde-cyanhydrin.
The principal adulterant of this oil is synthetic benzaldehyde which
is almost impossible to detect, unless it contains, as it very frequently
does, traces of chlorine, due to impurities formed in the course of manu-
facture.
l
Arch. der Pharm., 251 (1913), 85.