Oil of Bergamot
has a pale yellow color which becomes greenish when the oil is kept in copper vessels, and a strong agreeable odor. This oil requires the greatest care in its preservation, as it abstracts oxygen from the air with extreme rapidity, when it changes its superior odor so that it can hardly be distinguished from oil of turpentine.
Oil of Bitter Almond (Oleum Amygdale Amaræ),
when pure, is a colorless, refractive liquid which is heavier than water. The vessels in which this product is preserved must be stoppered air-tight, for in the air the oil very quickly changes into a white, odorless mass of crystals consisting of benzoic acid.
Oil of bitter almond is formed by the action of the amygdalin upon the emulsin present in the fruit, bitter-almond meal being deprived of fat and left in contact with water for some hours at from 40-45° C. (104-113° F.). Besides oil of bitter almond, sugar and prussic acid are likewise formed. The crude oil distilled from the meal is freed from the prussic acid by agitation with ferrous chloride and lime-water, and redistillation.
Oil of Cajeput (Oleum Cajuputi)
has usually a greenish color, and has a burning, camphoraceous and at the same time cooling taste. It has a peculiar odor resembling that of camphor and rosemary.
Oil of Calamus (Oleum Calami).
This oil, which is very viscid and of a yellow or reddish color, must usually be mixed with other essential oils in order to furnish pleasant perfumes.