Oil of eucalyptus is obtained by distillation from the fresh leaves of Eucalyptus Globulus, Labill. (N.O. Myrtaceae), and other species of Eucalyptus, which yield oils containing a large proportion of cineol, and but little phellandrene. The trees are natives of Australia and Tasmania, and are cultivated in Algeria and other of the Mediterranean countries. It is also official in the U.S.P.
It occurs as a light yellow, mobile liquid, with a pleasant, refreshing camphoraceous odour and a spicy taste, producing an after sensation of cold in the mouth. Specific gravity, 0.910 (B.P., 0.905) to 0.930 (0.905 to 0.925 at 25°); rotation, -10° to +10°.
Soluble in alcohol (3 in 1 or less), in all proportions of absolute alcohol, in 60 per cent. alcohol (1 in 38), in oils, fats, paraffins, and very slightly soluble in water. The oil from E. amygdalina, Labill., is less soluble in 60 per cent. alcohol (1 in 175).
Constituents.—The chief constituent of the oil is cineol (eucalyptol or cajuputol), C10H18O. Oils containing much cineol are said to solidify to a white crystalline mass when cooled in a freezing mixture of ice and salt. The assay process may be performed as follows:—To a known weight of the oil add, drop by drop, about half its volume of phosphoric acid (specific gravity, 1.750), keeping the mixture well cooled and continuously stirred (excess must be avoided; the reaction is complete as soon as a drop of the acid produces a red colouration). The crystalline magma formed, C10H18OH3PO4, is wrapped in fine calico, pressed between filtering paper, and when the adherent terpenes and phosphoric acid have been removed as far as possible, either by strong pressure or by washing with petroleum spirit, the crystals are decomposed by cold water in a graduated tube. After standing overnight, the cineol is measured, and from its specific gravity (0.930) the weight may be calculated. The separated cineol should readily crystallise on cooling to -3°, otherwise it is impure, and the process must be repeated. The oil should yield over 50 per cent. of cineol. Other constituents of eucalyptus oil are d-pinene (eucalyptene) and other terpenes, as well as various aldehydes, ethylic and amylic alcohols, and esters. Phellandrene, which is present in small quantities, forms a crystalline nitrosite with nitrous acid, and as it occurs abundantly in some oils of eucalyptus, especially that of E. amygdalina, and is an objectionable substance, it should be tested for by adding to 1 mil of the oil 2 mils of glacial acetic acid and 2 mils of a saturated aqueous solution of sodium nitrite. On shaking or stirring the mixture no crystals should be formed. "Lemon-scented " eucalyptus oil obtained from Eucalyptus maculata var. citriodora, Hook., contains 84 to 90 per cent. of citronellal, and is used for inhalation in a similar way to oil of Eucalyptus Globulus.
Action and Uses.—Oil of eucalyptus resembles the other essential oils in its action, though at one time credited with a specific action in malaria and fevers. It is employed as an antiseptic and deodorant, being largely used for inhalation. The oil is sprinkled on the handkerchief and inhaled frequently, for catarrhal colds and to prevent infection. Mixed with menthol, camphor, or pine oil it can be inhaled from a "dry" inhaler. As Vapor Eucalypti, it is inhaled with steam to relieve cough in chronic bronchitis and asthma. Pastilles, often with menthol or red gum, are much used in catarrhal colds with sore throat. Oily spray solutions for use in catarrh are prepared with eucalyptus and pine oils, and other ingredients such as cocaine, menthol, camphor, etc. It is used in bougies, suppositories, and pessaries, as an antiseptic, and to disguise the smell of iodoform. Antiseptic gauze, wool, and lint are prepared impregnated with oil of eucalyptus, for use as surgical dressings. Internally, eucalyptus oil is given in catarrhal inflammation of the mucous membranes, especially of the respiratory tract and bladder. It may be administered in capsules, or an emulsion may be prepared by shaking in a dry bottle 1 part of oil with 1 part of powdered gum acacia and adding 50 parts of water. Such an emulsion may also be used as an injection into the urethra or bladder. During excretion it causes the urine to smell of violets.
Dose.—1/4 to 2 decimils (0.025 to 0.2 milliliters) (1 to 3 minims), or more.
- Linteum Eucalypti, B.P.C.—EUCALYPTUS LINT. 5 percent.
- Nebula Eucalypti, B.P.C.—EUCALYPTUS SPRAY. 5 percent.
- Eucalyptus spray is used as an antiseptic for the throat and nose in dry catarrh. This spray is sometimes required of other strengths, but is not usually made stronger than 15 per cent.
- Nebula Eucalypti et Mentholis et Cocainae B.P.C.—EUCALYPTUS, MENTHOL, AND COCAINE SPRAY.
- Oil of eucalyptus, 1.25; menthol, 1; cocaine, 0.5; camphor, 1; liquid paraffin, to 100. A sedative and antiseptic spray for the throat and nose in catarrh and influenza, and to relieve coughing in asthma, bronchitis, and phthisis.
- Nebula Eucalypti et Pini, B.P.C.—EUCALYPTUS AND PINE SPRAY.
- Oil of eucalyptus, 5; oil of pine, 7.5; liquid paraffin, to 100. Used as a mild stimulant and antiseptic in laryngitis and chronic bronchial catarrh.
- Unguentum Eucalypti, B.P.—EUCALYPTUS OINTMENT.
- Oil of eucalyptus, by weight, 10; hard paraffin, 40; soft paraffin, white, 50. Add the oil of eucalyptus to the previously melted paraffins, and stir until cold. Eucalyptus ointment is employed as a mild antiseptic dressing, and as an application to haemorrhoids.
- Vapor Eucalypti, B.P.C.—EUCALYPTUS INHALATION, 1 in 25.
- Quantity sufficient for one inhalation, 4 mils (1 fluid drachm), to be added to 600 mils (1 pint) of water at 60°. Eucalyptus inhalation is employed in nasal catarrh, phthisis, chronic bronchitis, and asthma.
- Vapor Eucalypti Compositus, B.P.C.—COMPOUND EUCALYPTUS INHALATION. Syn.—Anti-catarrhal Salts.
- Oil of eucalyptus, 16.5; phenol, 16.5; oil of pine, 8.25; strong solution of iodine, 8.25; camphor, 16.5; ammoniated alcohol, 34. Pine sawdust or peat dust is saturated with this mixture, and then preserved in glass-stoppered bottles. Compound eucalyptus inhalation is used in coryza, hay fever, and influenza.
- Vapor Eucalypti et Mentholis Compositus, B.P.C.—COMPOUND EUCALYPTUS AND MENTHOL INHALATION. Syn.—Simplex Inhalant; Nebula Eucalypti Composita; Compound Eucalyptus Spray.
- Oil of eucalyptus, 10; oil of pine, 5; oil of cassia, 5; menthol, 5; thymol, 1 camphor, 2; tincture of benzoin, to 100. An excellent protective and antiseptic stimulant for use in a nebuliser in various conditions of the respiratory tract, and may be used with advantage as a basis for special medicaments. Thus, 2 per cent. of balsam of Peru may be added, as an antiseptic or stimulant; 1 to 2 per cent. of carbolic acid, in ulcerative conditions; 1 to 5 per cent. of cocaine for allaying pain and extreme irritation; 2 per cent. of creosote, for chronic bronchitis and pulmonary tuberculosis; 5 per cent. of oil of tar, for pulmonary tuberculosis; 1 per cent. of iodine, for chronic catarrhal conditions of the middle ear and 5 per cent. of terebene, for chronic coughs.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.