Oleum Amygdalae Amarae. Oil of Bitter Almond.
Synonym.—Oleum Amygdalae Essentiale.
Oil of bitter almond is obtained by distilling the moistened, bitter almond cake from which the fixed oil has been extracted by pressure. A similar oil, found in commerce, is obtained from the seeds of the apricot (Prunus Armeniaca, Linn.., which are imported in large quantities from Syria and California. When treated in the same way as bitter almonds, apricot kernels and peach kernels yield about 35 per cent. of fixed oil (Oleum Persicae), and about 0.6 to 1.0 per cent. of essential oil. The oil does not pre-exist in the almond cake, but is formed by the interaction of two constituents, amygdalin and emulsin, the products of the reaction being benzaldehyde, hydrocyanic acid, and dextrose. Hydrocyanic acid may be present in the natural oil to the extent of 4 or 5 per cent. When used in medicine it should contain not less than 2 per cent. and not more than 4 per cent. of hydrocyanic acid. Oleum Amygdalae Amarae, U.S.P., contains from 2 to 4 per cent. of hydrocyanic acid, and not less than 85 per cent. of benzaldehyde. For flavouring purposes the oil deprived of hydrocyanic acid (Oleum Amygdalae Essentiale sine Acido Prussico) should be used. To remove the hydrocyanic acid, the distilled oil is shaken with milk of lime and ferrous sulphate, whereby hydrocyanic acid is precipitated as calcium ferrocyanide; the unchanged benzaldehyde is then rectified by means of steam. In this way all traces of hydrocyanic acid are removed, and the oil may safely be used for any purpose. Another method of rectification is to shake the oil with a strong solution of sodium acid sulphite, which forms with the benzaldehyde a crystalline compound, from which the pure oil may be obtained by distilling with sodium carbonate. Oil of bitter almond occurs as a colourless liquid, having a characteristic odour; it is optically inactive. Specific gravity, 1.045 to 1.060 (1.040 to 1.055 at 25°). Boiling-point, 179°. On exposure to the air it is oxidised, and gradually deposits benzoic acid as a solid crystalline mass. This change takes place more readily in the oil freed from hydrocyanic acid, which evidently acts as a preservative. The presence of chlorine indicates contamination with, or substitution by, synthetically prepared benzaldehyde, although the latter, free from chlorine, has recently been placed on the market, so that the absence of chlorides is not an infallible indication of its purity. The following test may be applied to show the absence of chlorides:—Filter paper, free from chlorides, is moistened and placed on the inside of a large beaker. A folded strip of filter paper, saturated with the oil, is placed in a porcelain dish standing in a larger one, ignited, and immediately covered with the prepared beaker, which should be sufficiently large to cover the dish. The products of combustion are absorbed by the moistened paper, from which they are washed with distilled water, filtered, and treated with silver nitrate solution. No precipitate or even turbidity should be produced. To detect added nitrobenzene, dissolve 1 mil of the sample in 12 mils of absolute alcohol, and add 0.75 gramme potassium hydroxide; boil the liquid until it is reduced to about 4 mils, and leave it to cool; if the sample be pure no crystals form, but a brown colour is slowly developed, and the residual liquid is entirely soluble in water. In presence of nitrobenzene brown crystals of azoxybenzene, C12H10N2O, are formed, which are insoluble in water, and may be collected, dried by pressure, and weighed.
Sparingly soluble in water; soluble in all proportions of alcohol, ether, fixed, or volatile oils. Nitric acid dissolves the oil at ordinary temperatures without generation of nitric oxide vapours.
Action and Uses.—Oil of bitter almond is employed as a flavouring agent for emulsions, and for use in domestic culinary operations. For the latter purpose the oil freed from hydrocyanic acid should be used.
Dose.—1 to 6 centimils (0.01 to 0.06 milliliters) (1 to 1 minim).
- Aqua Amygdalae Amarae, U.S.P. and B.P.C.—BITTER ALMOND WATER. 1 in 1000.
- Used as a flavouring agent. Dose.—2 to 8 mils (½ to 2 fluid drachms),
- Aqua Amygdali Amarae, P.I.—BITTER ALMOND WATER, P.I.
- Strength, 0.1 per cent.
- Essentia Amygdalae Composita, B.P.C.—COMPOUND ESSENCE OF ALMOND.
- Oil of bitter almond free from hydrocyanic acid, 0.52; tincture of vanilla, 40; tincture of benzoin, to 100. Used as a flavouring agent,
- Spiritus Amygdalae Amarae, C.F., and U.S.P.—SPIRIT OF BITTER ALMOND. Syn.—Essence of Bitter Almonds,
- Oil of bitter almond, 1; alcohol (95 per cent.), 80; distilled water, to 100. Used chiefly as a flavouring agent. Average dose.—5 decimils (0.5 milliliters) (8 minims).
- Syrupus Amygdalae, U.S.P.—SYRUP OF ALMOND.
- Spirit of bitter almond, 1; orange-flower water, 10; syrup, to 100. Average dose.—4 mils (1 fluid drachm).