Related entries: Amygdala.—Almond - Oleum Amygdalae Expressum (U. S. P.)—Expressed Oil of Almond
"A volatile oil obtained from bitter almond by maceration with water, and subsequent distillation. It should be kept in small, well-stoppered bottles, protected from light"—(U.S. P.).
SYNONYM: Oleum amygdalarum (amararum) aethereum.
Preparation and Chemical Composition.—The greater quantity of commercial oil of bitter almond is prepared from the seeds of apricots, which yield an oil identical with that from bitter almond (Gildemeister and Hoffmann, Die Aetherischen Oele, Leipzig, 1899, p. 572). The seeds are first deprived of their fixed oil by subjecting them, ground, to a hydraulic pressure of 350 atmospheres. Bitter almonds yield 50 per cent, apricots 35 to 38 per cent of fatty oil. The powdered press-cake is then mixed with about 6 parts, by weight, of water, the mixture allowed to digest at about 50° C. (122° F.) for some 12 hours; the oil is then distilled off with steam. Oil of bitter almond does not preexist in the kernels, but is produced in the presence of water by the action of the ferment emulsin upon the glucosid amygdalin, whereby dextrose, oil of bitter almond, and hydrocyanic acid are formed, thus: C20H27NO11 (amygdalin) + 2H2O (water) =2C6H12O6 (glucose) + C7H6O (oil of bitter almond) + HCN (hydrocyanic acid). Time must be allowed this chemical decomposition to take place, and the temperature must not be too high, or else the fermentative power of emulsin will be destroyed (compare Amygdala Amara and Laurocerasus).
The yield of the oil from bitter almonds is 0.5 to 0.7 per cent; from apricots, 0 6 to 1 per cent. It consists of benzaldehyde (C6H5CHO) and hydrocyanic acid, the former being easily convertible by oxidation into benzoic acid. This change is favored by removal of hydrocyanic acid. The quantity of the latter may normally vary from 1.5 to 4 per cent (F. B. Power, Essential Oils, published by Fritzsche Brothers, 1894). A third body may occur in the oil, namely the nitril of mandelic acid (C6H5.CHOH.CN), which is merely an addition product of equal molecules of benzaldehyde and hydrocyanic acid. It forms when both substances are in prolonged contact with each other, and is decomposed into its constituents by steam heat. It is therefore not present in the fresh oil. It has the specific gravity 1.124, while the normal oil has the specific gravity of 1.045 to 1.060. Thus a high specific gravity of the oil (exceeding 1.070) indicates the presence of dangerous proportions of hydrocyanic acid. As to the method of valuation of hydrocyanic acid in bitter almond oil, see paper by Prof. Edward Kremers and O. Schreiner, in Pharm. Review, 1896, p. 196. The oil may be completely deprived of its hydrocyanic acid by shaking with milk of lime and ferrous sulphate, whereby insoluble calcium ferrocyanide is formed (Gildemeister and Hoffmann, loc. cit.). The crude oil may also contain benzoin (C14H12O2), a solid, crystallizable substance formed by polymerization of benzaldehyde.
Description.—Oil of bitter almond is officially described as "a clear, colorless or yellowish, thin, and strongly refractive liquid, having a peculiar, aromatic odor, and a bitter and burning taste. Specific gravity, 1.060 to 1.070 at 15° C. (59° F.). Boiling point, about 180° C. (356° F.). Optically inactive. Soluble in 300 parts of water at 15° C. (59° F.)., and in alcohol or ether in all proportions; also soluble in nitric acid at ordinary temperatures without the evolution of nitrous vapors. In the fresh state the oil is neutral to litmus, but when kept for some time it assumes an acid reaction, due to the formation of benzoic acid"—(U. S. P.). Warm nitric, or fuming nitric acid converts it into nitrobenzaldehyde and benzoic acid.
Tests.—The U. S. P. gives the following tests: "If 10 drops of the oil, dissolved in a little alcohol, be shaken with a few drops of a strong solution of sodium hydrate, then with a little ferrous sulphate T.S., and finally mixed with a slight excess of hydrochloric acid, a blue precipitate will be produced (presence of hydrocyanic acid). The presence of artificial oil containing chlorinated products may be detected in the following manner. Fold a small strip of filter paper in the form of a taper, saturate it with the oil, and lay it in a small porcelain capsule. Set this capsule into a larger one, and provide a large beaker to be inverted over the capsule containing the taper. Then, having moistened the inner surface of the beaker with distilled water, ignite the taper, immediately invert the beaker over the capsule, and allow the products of combustion to be absorbed by the water in the beaker. If the beaker be now rinsed with a little distilled water, and the liquid filtered, the filtrate should yield no turbidity with silver nitrate T.S. If 5 Cc. of the oil be vigorously shaken, in a flask, with 50 Cc. of a cold, saturated solution of sodium bisulphite, and the mixture heated for a few minutes on a water-bath, the odor of the oil should disappear, and a nearly clear solution be formed, without the separation of any oily drops oil the surface of the liquid (absence of most other volatile oils and of nitrobenzol)"—(U. S. P.). The latter test depends on the property of aldehydes to enter into crystallizable, inodorous addition-compounds with sodium bisulphite. Thus: C6H5.CHO + NaHSO3 = C6H5.CHOH.SO3Na (also see test under Nitrobenzenum). Another rapid and simple test for artificial oil containing chlorine compounds depends upon the distinct, but evanescent, green-flame coloration imparted to the flame of a Bunsen burner by a clean copper wire when moistened with the oil in question, the coloration being due to the vapors of copper chloride (F. B. Power, loc. cit.).
ARTIFICIAL OIL OF BITTER ALMOND, or pure benzaldehyde (benzoic aldehyde) C7H6O, or C6H5.COH, is now extensively prepared, in Europe, from certain chlorine substitution products, e. g., benzalchloride (C6H5.CHCl2), of the fluid coal-tar hydrocarbon toluene (C6H5.CH3). This artificial product is now frequently used; it is naturally free from hydrocyanic acid, but has a slightly peculiar smell owing to the presence of traces of chlorine compounds, which are difficult to remove (see Tests).
Action, Medical Uses, and Dosage.—The medicinal uses of this agent are those named under diluted hydrocyanic acid, which see. It is used in the arts to give flavor and odor to candies, and in pharmacy to flavor castor and cod-liver oils. It is extremely poisonous, 1 drop having proved fatal to small animals, and 15 drops to an adult. Locally (oil, 1 drop, to water, 1 fl℥) it allays itching. The maximum dose internally should not exceed one-half minim, given in emulsion with sugar, water, and acacia.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.