A Manual of the Chemistry of the Carbon Compounds

460 THE CMEMI8TRY OF
ferment of bitter almonds) is added to the aqueous solution, it splits
up into prussie acid, benzaldehyde, and glucose:—
0 { CflHBCO)
I + 2H2O = CNH + C6H5.COH + 2C9Hli!O<
Emulsin loses its active properties when heated to 100"; therefore
in preparing oil of bitter almonds the paate must be mixed with cold
water, and alowed to stand for some time before it is distilled.
Salicin CMH«O7 is found in the young bark of several species of
•wilow and poplar, and in castoreum (the prepulial follicles of the
beaver). It is obtained by exhausting the bark with boiling water,
and digesting the concentrated solution with lead oxide, to remove
gum, tannic acid, &c. After filtering, the liquid is treated with
hydrogen sulphide, and the clear solution evaporated to the consistency
of a syrup. On standing, salicin crystallizes out in colourless
prisms, melting at 198°, and possessing a bitter taste.
By the action of emulsin or saliva on its aqueous solution it is resolved
into glucose and saligenin, or salicyl alcohol:—
SftS;} 0 + H2O = C6H12O6 + CaH4(0H)CH3.OH
Chromic acid-solution oxidizes it to s&lieylaldehyde, formic acid
and carbon dioxide.
Populin C^HjgOj + 2H2O occurs with salicin in the barks and
leaves of the aspen, and is separated from salicin by precipitating it
with potassium carbonate from the aqueous solution. It crystallizes
in smal prisms having a sweet taste. Boiling baryta-water resolves
it into salicin and benzoic acid:—•
Vopulin has been produced artificially by tha action of benzoyl
•hloride on salicin.
Helicin CUHWO7 is obtained by oxidizing salicin with dilute nitric
icid. It is a crystalline substance, having a slightly bitter taste. By
preating it with eniulsin or dilute acids it yields glucose and salieyl-
.aldehyde:—
C18HwOy exists in the leaves of the bearberry (Arbutus
Ura-wrsi), from whioh it is obtained hi the same way as salicin fro
wilow-bavk. It is freely soluble in water, and crystallizes in needles
having a bitter taste. Emulsin or dilute acids decompose it into
glucose and hydroquinone:—