This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The oil of bitter almond is obtained from the seeds of Amygdahis communis, var. amara, Linne. The bitter almonds are deprived of most of their fixed oil by pressure between warm plates; the press-cake is powdered, mixed with about six times its weight of water, the mixture digested for a day or two at a temperature of about 50° C. (122° F.), and then distilled. The tree grows wild in Southern Europe, Africa, especially Palestine and Syria, and is also cultivated there, and has been introduced in the warmer parts of the United States (California) and other countries. Oil of bitter almond is colorless or yellowish, limpid, has a peculiar aromatic odor, resembling that of hydrocyanic acid, and a bitter and burning taste. Freshly prepared, it has in alcoholic solution a neutral reaction to test-paper, but old oil changes the color of blue litmus to red. It varies in spec. gr. between 1.06 and 1.075, and boils at about 180° 0. (356° F.).
The principal adulterations are nitrobenzol, alcohol, and chloroform, the last two being sometimes used together to leave the specific gravity unchanged. By distilling a little of the suspected oil from a test tube placed in a water-bath kept at a temperature not exceeding 65° C. (149° F.), the chloroform will distil over, while alcohol will distil at 80° 0. (176° F.), the distillates showing the behavior of these compounds. On dropping oil of bitter almond containing alcohol into water, the drops, while floating or subsiding in the water, will become milk-white. Nitrobenzol (see Artificial Oil of Bitter Almonds) has an odor similar to that of bitter almond oil and a sweet taste, and is nearly insoluble with water.