178 ODOROGRAPHIA. 
the albuminoids present. In order to remedy this difficulty, and 
to get all the amygdalin into solution, 12 parts of the coarsely 
powdered cake are immersed in 100 to 120 parts of boiling 
water, and kept at the boiling-poimt for 15 to 30 minutes; this 
coagulates the albuminous matters and dissolves the amygdalin, 
then, after cooling the mixture, an emulsion of one part of pow- 
dered almonds (either sweet or bitter, or a portion of the first- 
mentioned cake) stirred up in six or seven parts of cold water is 
added to the mass. This one part contains sufficient emulsin to 
produce the desired decomposition, at a temperature not exceeding 
40°C. The entire bulk is then rapidly distilled. By this process 
the oil is prepared on a large scale, the yield varying from 0°74 to 
1:67 per cent. of oil from the cake. Therefore, if 100 lbs. of 
almonds yield 57 lbs. of cake, the yield of oil is 0°42 to 0°95 per 
cent. on the weight of the almonds. The aqueous distillate con- 
tains some oil in solution which is removed by a subsequent 
distillation. The great variation in the figures of the yield is 
partly accounted for by the variability of quality of the almond 
used, and the consequent varying amount of amygdalin present, 
and it is partly due to admixture of sweet almonds; an adultera- 
tion which frequently causes much loss to the manufacturer, whose 
profit greatly depends on the percentage of essential oil which he 
can distil from the residuary cake. 
Natural Oil of Bitter Almonds. 
This is chemically known as Benzaldehyde. It is a colourless, 
strongly refractive liquid, having the well-known characteristic 
smell and a burning aromatic taste. It dissolves in more than 
300 parts of water, boils at 179°, and has a sp. gr. of 1:0636 at 0°, 
and of 1:0504 at 15°. 
This oil is generally adulterated; in many cases with alcohol. 
When pure, sulphuric acid produces a clear crimson-red colour 
without visible decomposition. Mixed with an alcoholic solution 
of potash, crystals are eliminated. Iodine dissolves only partially 
and slowly init. Nitric acid, sp. gr. 1:42, causes no immediate 
reaction, and in the course of three or four days crystals of 
benzoic acid begin to appear, but if only 8 per cent. or 10 per 
cent. of alcohol or rectified spirit is present a violent effervescence 
speedily commences, and nitrous fumes are evolved. By using 
