176 ODOROGRAPHIA. 
The bitter almonds resemble sweet almonds in shape; but are 
generally somewhat smaller. In the order of their relative value 
they are known as French, Sicilian, and Barbary almonds. The 
fixed oil contained in the bitter almond is identical with that con- 
tained in the sweet variety, but in a slightly smaller proportion ; 
the average yield being 43 to 44 per cent., obtained by hydraulic 
pressure. After the almonds have been freed from fixed oil by 
pressure, an odourless cake is left which yields the characteristic 
smell of oil of bitter almonds on the addition of water. The 
chemists who made this discovery thereby concluded that oil of 
bitter almonds must be a compound of water with a peculiar 
principle which they endeavoured to isolate. The use of water 
being impossible, they extracted the pressed almonds with boiling 
alcohol, and obtained, together with resin and a liquid sugar, a 
crystalline compound containing nitrogen, to which they gave the 
name of amygdalin. 'This compound, to which the taste of bitter 
almonds is due, gave no smell of bitter almonds when treated with 
water, nor did either of the two other compounds, nor the residue, 
nor either a mixture of them all*. The prussic acid and the oil 
of bitter almonds had vanished from their hands (Robiquet and 
Boutron-Charlard). The problem was solved by Liebig and 
Wohler+, who also accurately determined the composition of 
amygdalin. They showed that both sweet and bitter almonds 
contained a peculiar nitrogenous substance, emulsint, which 
converts amygdalin, in presence of water, into oil of bitter 
almonds, prussic acid, and grape sugar. To the oil of bitter 
almonds they gave the name of benzoyl-hydride, which was later 
* Annales de Chim. et de Phys. xliv. p. 352. 
+ Ann. Chem. Pharm. xxii. p. 1; xxv. p. 175; xxv. p. 190. 
¢ To prepare emulsin:—Sweet almond paste, well freed from fixed oil, is 
macerated in three times its weight of pure water; the mass is pressed, and 
the emulsin thus obtained is left to itself at 20° to 25°C. After the lapse of a 
day, the emulsin is found to have separated into two layers, the upper of 
which is coagulated, and looks like cream, while the lower is watery and 
transparent. After two or three days this watery liquid no longer gives a pre- 
cipitate with acetic acid, but it forms with alcohol a precipitate perfectly 
soluble in water. This last precipitate consists of emulsin. After being 
washed with absolute alcohol and dried zm vacuo over sulphuric acid it forms 
a white, opaque, friable mass, soluble in water. 
Emulsin completely loses its power of transforming amygdalin into benz- 
aldehyde when its aqueous solution is boiled, but it retains its power when heated 
to 100° C. in the dry state, even for several hours. 
