Oleum Thymi. U. S. Oil of Thyme.
Ol. Thymi [Thyme Oil]
Related entry: Thyme
"A volatile oil distilled from the flowering plant of Thymus vulgaris Linné (Fam. Labiatae), and containing not less than 20 per cent., by volume, of phenols. Preserve it in well-stoppered, amber-colored bottles, in a cool place, protected from light." U. S.
Huile volatile de Thym, Fr. Cod.; Essence de Thym, Fr.; Oleum Thymi, P. G; Thymianol, G.; Esencia de tomillo, Sp.
In the south of France thyme grows wild in great abundance, and is largely collected for distillation. The oil is taken from France to England, and thence reaches this country under the name of oil of origanum, having, probably from its greater cheapness, been substituted for the latter.
Thymus vulgaris is a very common plant, indigenous to Southern Europe, and cultivated in our gardens. It possesses a subcampanulate two-lipped calyx, villous in the throat; corolla limb two-lipped, the upper erect and emarginate, the lower spreading, three-cleft. It is a low under-shrub, procumbent at the base, with ovate-linear, revolute leaves, the flowers occurring in a whorled spike. The herbaceous portion, which should be gathered when the plant is in flower, has a peculiar, strong, aromatic, agreeable odor, not lost by drying, and a pungent, aromatic, camphoraceous taste. Its active constituent is the volatile oil, which is obtained separate by distillation with water.
The oil, as prepared in Southern France, is, after one distillation, of a reddish-brown color, and called the red oil, but when again distilled is colorless, and in this condition is distinguished as the white oil. Oil of thyme is officially described as "a colorless or red liquid, having a characteristic odor and taste. It is soluble in 2 volumes of 80 per cent. alcohol. Specific gravity: 0.894 to 0.930 at 25° C. (77° F.). It is slightly laevorotatory. Shake 1 mil of the Oil with 10 mils of hot distilled water, and, after cooling, pass the aqueous layer through a wetted filter; the filtrate does not assume a blue or violet color upon the addition of a drop of ferric chloride T.S."
According to Zeiler, one pound of the fresh herb yields 45.7 grains of the oil, of the dried herb 38 grains. The oil, as found in commerce, is of a reddish-brown color, and of an odor recalling that of thyme, but less agreeable. Its specific gravity is stated at 0.905, but probably varies, as the oil is a complex body. The more volatile portion, that coming over below 180° C. (356° F.) in distillation, is a mixture of cymene, C10H14, boiling at 175° C. (347° F.), and pinene, C10H16, boiling at 161° C. (321.8° F.). The less volatile and most valuable portion is chiefly thymol, C10H14O, a white crystalline solid, melting at 50° C. (122° F.), and possessing a pungent taste. Carvacrol is also present, at times replacing part or all of the thymol, and in addition linalool and bornyl acetate have been found in small amount. (See Proc. A. Ph. A., 1897, 637.)
The true oil of thyme, according to Bennett (P. J., 1908, lxxx, p. 803), differs from the various oils known commercially under this name, as well as the oils of origanum, in that it contains thymol, while the other oils of thyme contain the isomeric carvacrol. While it is probable that carvacrol has similar therapeutic properties to thymol, it has not been employed in medicine to any considerable extent and is far less well known.
The oil is commonly adulterated with the oil of turpentine, the white oils being especially impure. The presence of oil of turpentine, according to Duyk (J. P. A., 1899, 41), is due to the fact that the French peasants place in the body of the still as a foundation for the herbs a layer of pine and fir branches.
The annual production of oil of thyme at Grasse, according to Fluckiger (A. J. P., 1885, 132), amounted to 40,000 kilogrammes.
Oil of thyme has been largely replaced in medicine by thymol. According to Camperdon, in doses of from three to fifteen grains (0.2-1.0 Gm.), oil of thyme causes mental excitement, and is a valuable diffusible stimulant in collapse. It is powerfully germicidal. (See Thymol.)
Dose, three to five minims (0.2-0.3 mil).
Off. Prep.—Liquor Antisepticus, N. F.; Liquor Zinci et Alumini Compositus, N. F.; Liquor Zinci et Ferri Compositus, N. F.; Mistura Oleo-Balsamica, N. F.; Oleum Hyoscyami Compositum, N. F.