Related entry: Eucalyptus (U. S. P).—Eucalyptus
"A volatile oil distilled from the fresh leaves of Eucalyptus globulus, Labillardière; Eucalyptus oleosa, F. von Mueller, and some other species of Eucalyptus (Nat. Ord.—Myrtaceae). It should be kept in well-stoppered bottles, in a cool place, protected from the light"—(U. S. P.).
History and Description.—When the leaves are distilled with steam, and the distillate purified by treatment with caustic soda solution and again rectified, a fragrant, yellowish oil is obtained, which becomes brown and resinous from oxidation, when exposed to the atmosphere. Eucalyptus tar is the soap-like, brown residue from the purification of the crude oil with caustic soda. It is sometimes used as a cheap disinfectant. The flower buds yield eucalyptus oil in great quantity, and even when dry are found to contain numbers of large oil glands filled with oil. As described by the U.S. P., it is "a colorless or faintly yellowish liquid, having a characteristic, aromatic, somewhat camphoraceous odor, and a pungent, spicy, and cooling taste. Specific gravity, 0.915 to 0.925 at 15° C. (59° F.). Soluble, in all proportions, in alcohol, carbon disulphide, or glacial acetic acid. Its alcoholic solution is neutral, or slightly acid, to litmus paper. If 1 Cc. of the oil be mixed with 2 Cc. of glacial acetic acid, and 1 or 2 Cc. of a saturated, aqueous solution of sodium nitrite be gradually added, the mixture, when gently stirred, should not form a crystalline mass (distinction from oils of eucalyptus containing a considerable portion of phellandrene)"—(U. S. P.). The oil, if rich in cineol, solidifies when surrounded by a freezing mixture; it dissolves resins readily, but does not dissolve gutta-percha. The oils of various species of Eucalyptus differ in many respects. Since 1854, the manufacture of eucalyptus oil has been established in Australia by Joseph Bosisto, and it is now an article of considerable commerce. (In this connection, see an interesting article by Mr. E. M. Holmes, on the manufacture, etc., of eucalyptus oil, in Pharm. Jour. Trans., Vol. XXV, 1894, p. 501.) Large quantities of the oil are now also produced in Algeria.
Chemical Composition.—The oil of Eucalyptus globulus contains cineol (C10H18O, Jahns, 1884), formerly called eucalyptol (Cloëz, 1870). It is the chief constituent of this oil, as well as oil of cajuput (which see), and occurs in smaller quantities in a number of other oils (see enumeration, in Gildemeister and Hoffmann, loc. cit.). It is a colorless fluid of a characteristic camphoraceous odor, and crystallizing slightly below the freezing point of water. It boils at 177° C. (350.6° F.), and is optically inactive. It forms crystallizable addition compounds, chiefly with hydrobromic acid gas and with concentrated phosphoric acid, which serve in the isolation, and perhaps the quantitative determination of cineol.
The oil of Eucalyptus globulus also contains the hydrocarbon dextro-pinene (Wallach and Gildemeister, 1884), formerly called eucalyptene, and other hydrocarbons. The crude oil contains valeric, butyric, and caproic aldehydes, to which the acrid odor of the oil is due. The oil of the Australian E. amygdalina, Labillardière, or White and Brown peppermint tree, contains chiefly phellandrene, with little cineol. The aldehyde citronellal (C10H18O) is the principal constituent (80 to 90 per cent) of the oil of E. citriodora, Hooker, and other species; and citral (C10H16O) is found in large quantity in the oils from Eucalyptus Staigeriana, F. von Mueller, and Backhouxia citriodora, F. von Mueller. E. oleosa, F. von Mueller, contains cineol and cumin-aldehyde. (For abundant information regarding eucalyptus oils, see Gildemeister and Hoffmann, Die Aetherischen Oele, 1899.)
Action, Medical Uses, and Dosage.—(For uses, see Eucalyptus.) Dose, 2 to 10 drops.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.