Besides the oil from the root, one obtained from the seeds also occurs in commerce. It is, however, more expensive. In a fresh state it is amber-yellow, and has a specific gravity of 0.8549 at 59° F.; older oil is thickly-fluid, brown, and has a specific gravity of O.9086. It contains a terpene which turns the plane of polarization to the right, and has a lemon-like odor. It is used for fine perfumery.
Anise-seed oil (oleum anisi). The anise (Pimpinella anisum L.), natural order Umbelliferae, contains volatile oil in all parts, but chiefly in the seeds. Dry anise-seed yields by distillation 2½ to 3 per cent. of oil, while the peduncle and chaff contain at the utmost 1 per cent. of oil, which is said to be richer in stearoptene. The anise-seed oil prepared in Southern Russia has always been highly valued, but as it is generally considerably adulterated, the Leipsic manufacturers of volatile oils prefer to import the seed and distill it themselves.
Freshly prepared anise-seed oil is colorless or straw-yellow, has the odor of anise and a sweetish taste, leaving a burning sensation upon the tongue. It is thinly fluid at 68° F., but commences to congeal at a somewhat lower temperature, and the sooner the more stearoptene it contains. Good oil should become solid at from 57.2° to 60.8° F. It has a specific gravity of 0.980 to 0.995 at 59° F. The specific gravity varies with the content of stearoptene; the greater the latter the higher the specific gravity. Good anise-seed oil contains 5 to 10 per cent. of terpene and 90 to 95 per cent. of a stearoptene, called anethol, C10H12O, on which the value of the oil depends. The anethol can be separated from the oil by cooling to 32° F., and forms colorless crystals. It has an agreeable odor and intensely sweet taste, is sparingly soluble in water, but readily in alcohol, ether, and other solvents of volatile oils. Good anethol has a specific gravity of 0.986, and melts at 69° to 70° F. By frequent contact with the air a small portion of the anethol is oxidized, very likely to anisaldehyde. By this process the specific gravity is raised and the melting point lowered.
Anise-seed oil is soluble in 5 parts of 90 per cent. alcohol, and with 3½ times its volume of petroleum-ether yields a clear mixture. Its mixture with four times its weight of petroleum-ether is turbid, but becomes clear in ten minutes, while that with five times its volume of petroleum-ether remains for a longer time turbid. In a fluid state the oil, when exposed to the air, becomes resinous and loses its property to crystallize. It should, therefore, be kept in tightly-closed bottles in a cool, shady place.
Anise-seed oil is used in perfuming soaps and mouth waters. It should, however, be used with prudence, since the sweetish, penetrating odor of the oil readily overcomes the other volatile oils in the mixture, and renders them inoperative.
Star anise oil very much resembles the ordinary anise-seed oil. It is obtained from star anise, the fruit of Illicium anisatum, a tree formerly supposed to be indigenous to Cochin China, and cultivated in China, Japan, and the Phillipine Islands. However, according to Messrs. Bourgeoin-Meiffre, a French firm of Hanoï (Tonkin), the star anise oil found in commerce is exclusively produced in the French colony Tonkin (Province Langson), the French government having made over the entire sale of the oil to the above-mentioned firm.
According to a memoir published by Dr. Blondel, of Paris, the star anise tree is not indigenous to the Chinese provinces Yunnan, Quang-si, and Fo-Rien, but to the province Langson, which has by conquest passed into French possession. Hence, the producers of star anise and star anise oil are now under French control and, as it seems, are obliged to sell all the oil produced to the above-mentioned firm. If these statements should prove correct, the Chinese harbors Macao and Hong Kong, from which the greater portion of star anise oil was formerly exported, will lose their importance in this respect and the product find its way direct from Hanoï via Hayphong to Marseilles. The first shipment from Bourgeoin-Meiffre arrived in Europe in December, 1890. According to Messrs. Schimmel & Co.'s report, the product is put up and packed exactly like that formerly shipped from Hong Kong, and the oil of excellent quality.
Star anise oil differs from the ordinary oil in containing a much smaller quantity of anethol, and hence congealing only at a temperature of from 41° to 50° F. Besides the odor of the terpene contained in star anise oil differs from that of the ordinary oil. Admixtures of star anise oil can, therefore, be generally recognized by the odor. Other methods recommended for its detection are unreliable.
Balm oil.—The leaves of this plant, Melissa officinalis, yield by distillation a volatile oil sometimes called oil of melissa. It is colorless or yellowish, of a pleasant odor, has a specific gravity of 0.85 to 0.92, shows a slightly acid reaction and dissolves in 2 to 3 parts of alcohol. It must not be confounded with the so-called East India oil of melissa or citronella oil from Andropogon Nardus L. Balm oil is occasionally used in the preparation of eau de Cologne.