Synonyms.—Oleum Myrciae; Oil of Bay.
Oil of pimento leaves is obtained by distillation from the leaves of Pimenta acris, Wight (N.O. Myrtaceae), and probably other closely allied species, plants flourishing in the West Indies, especially St. Thomas, Jamaica, etc. The oil is distilled into water, where it separates into two portions-a light fraction, distilling over rapidly, and a heavy fraction distilling more slowly, the former floating on the top of the water, the latter sinking. These are mixed to obtain a normal oil. Oil of pimento leaves occurs as a yellow liquid, soon becoming brown on exposure to the air, having a pleasant, characteristic odour, and a sharp, spicy taste. Specific gravity, 0.945 to 0.975. Slightly laevorotatory, up to -6°. Oil of pimento leaves may be adulterated with the oils of cloves and pimento, or occasionally with oil of turpentine. The two former cause increase of specific gravity, and, as the oil contains no pinene, turpentine may be detected in the following manner:—The oil is distilled, and the first 10 per cent. of distillate is mixed with an equal volume of amyl nitrite and two volumes of glacial acetic acid; this mixture is cooled in ice and salt, and a mixture of equal parts of glacial acetic acid and strong hydrochloric acid added drop by drop so long as a blue colour is developed. If pinene be present a white crystalline precipitate of pinene nitrosochloride, C10H16NOCl, is produced. The presence of 10 per cent. of oil of turpentine may be detected with certainty in this way.
Soluble, when freshly distilled, in air equal volume of alcohol forming a clear solution. On keeping, however, the oil becomes less soluble, and it then gives only turbid mixtures with alcohol. This is due to polymerisation of the olefinic terpene myrcene, contained in the oil.
Constituents.—The following constituents are present in the oil:—Eugenol, C10H12O2, 40 to 55 per cent.; myrcene, C10H16; chavicol, C9H10O; methyl-eugenol, C11H14O2; methyl-chavicol, C10H12O; l-phellandrene, C10H16; citral, C10H16O; the phenols to the extent of 59 to 65 per cent. Myrcene, on treatment with glacial acetic acid and sulphuric acid, yields dipentene and an oil of a lavender-like odour, which yields linalool after saponification, identified by its conversion into citral. Myrcene, therefore, bears the same relation to linalool as camphene to isoborneol, and pinene or dipentene to terpineol.
Uses.—Oil of pimento leaves is not employed in medicine, but is used in the preparation of bay rum.
- Spiritus Pimentae Compositus, B.P.C.— COMPOUND SPIRIT OF PIMENTO. Syn.—Spiritus Myrciae; Bay Rum.
- Oil of pimento leaves, 0.75; oil of orange peel, 0.05; oil of pimento, 0.05; alcohol, 64; purified talc or kaolin, a sufficient quantity; distilled water, to 100. Used as a wash for the hair, and as an astringent application to the face after shaving.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.