Oil of ajowan is obtained by distillation from the fruits of Carum copticum, Benth. and Hook. f. (N.O. Umbelliferae), in which it exists to the extent of from 3 to 4 per cent. Indigenous to and cultivated in India. Ajowan oil is official in India and the Eastern Colonies as a carminative, like oils of anise, caraway, dill, and peppermint. It occurs as an almost colourless or brownish liquid, having the odour of thyme and a sharp burning taste. Specific gravity, 0.917 to 0.930. It is slightly dextrorotatory.
Constituents.—The oil contains from 45 to 55 (I.C.A., 30 to 36) per cent. of thymol (C10H14O), for which alone it is distilled in Europe. The thymol crystallises partially from the oil, complete separation being effected by shaking with solution of sodium hydroxide to form sodium thymol, from which thymol is liberated by means of hydrochloric acid, and may be finally recrystallised from alcohol. The remainder of the oil consists of cymene (C10H14), boiling at 175°, and a terpene boiling at 172°, with traces of pinene and dipentene, the mixture being known commercially as "thymene."
Action and Uses.—Oil of ajowan is employed in India as an antiseptic and aromatic carminative. Its action and uses are similar to those of thymol.
Dose.—1/4 to 2 decimils (0.025 to 0.2 milliliters) (1/2 to 3 minims).
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.