Oleum Olivae.—Olive Oil.
"A fixed oil expressed from the ripe fruit of Olea europaea, Linné (Nat. Ord.—Oleaceae). It should be kept in well-stoppered bottles, in a cool place"—(U S. P.).
SYNONYM: Sweet oil.
ILLUSTRATION: (Tree) Bentley and Trimen, Med. Plants, 172.
Botanical Source.—The olive-tree is an evergreen, from 12 to 20 feet high, with hoary, rigid branches, and a grayish bark. The leaves are opposite, lanceolate, or ovate-lanceolate, mucronate, short-petioled, green above, and hoary on the underside. The flowers are small, in short, axillary, erect racemes, very much shorter than the leaves. The corolla is short, white, with 4 broad, ovate segments; the calyx short and 4-toothed. Stamens 2, rather projecting; style very short; stigma bifid, with emarginate segments. The fruit is a drupe about the size of a damson, smooth, purple, 2-celled, with a nauseous, bitter flesh, inclosing a sharp-pointed Stone (L.).
History.—The native country of the olive-tree is unknown; it is supposed to have been originally from Asia, since it is mentioned in the Bible. At present it is extensively cultivated in the south of Europe, especially in Spain, France, Sicily, Italy, Calabria, and Apulia. It has been introduced into South America, California, and our southern states; in the latter section it does not thrive successfully, but in California it promises to have a commercial future. The tree commences yielding fruit in its third year; in its sixth year it is very productive, and remains so for an indefinite length of time. Varieties of the tree are based on the size, color and taste of fruit, and character of the foliage. The bark of the tree was formerly used in medicine, as well as the leaves, which have a bitter and acrid taste. In the warmer provinces of Europe a substance exudes from the bark, which has been called Gomme d'Olivier, and which, according to Pelletier, consists of a peculiar resin containing a small quantity of benzoic acid, and a peculiar crystalline principle, which he called olivin or olivile. This was at one time used as a remedial agent. The fruit, gathered when not quite ripe, is very solid, bitter, and acrimonious; but when steeped for several days in a lye of wood ashes, and then pickled in brine, it constitutes the olive of commerce, much valued by many as a food. According to Flückiger, the bitterish seeds yield a bland, non-drying oil, which, when obtained together with that of the pulp, amounts to 1/40 of the whole quantity. The leaves and fruit of this tree, before maturing, contain mannit, but when the fruit has ripened this substance has wholly disappeared.
Preparation.—The oil is obtained by expression from the fleshy pericarp of the fruit. The fruit is carefully collected immediately previous to its ripening, or when it assumes a reddish hue, one day usually completing the gathering; if the olives be collected when fully ripe, the tree will bear only every other year. Without delay, the drupes are passed through a mill, having its stones so arranged as not to break the olive nuts; the pulpy mass thus obtained undergoes cold expression, from which the finest oil, termed virgin oil, is procured. The residual press-cake is crushed, dampened with boiling water, and again exposed to pressure, thus yielding a second-rate oil, which is made use of as a salad oil and for preparing fine soaps; it is the ordinary olive oil of commerce. Upon again breaking up the press-cake, steeping it in water, allowing it to remain for 10 or 12 days, until it begins to ferment, and then expressing it, an inferior oil is obtained, which is used in lamps, and for making plasters, inferior soaps, etc. Carbon disulphide is sometimes used to extract residual oil in marc that has already been treated with pressure and water. Such an oil is very inferior. The process here described is followed in more or less modified form in the different olive-growing countries.
Description.—The best grade of olive oil comes from the south of France (Provence oil), and from Italy (Lucca oil, Gallipoli oil, etc.). Spain and, recently, California yield good grades of olive oil. Olive oil that is dark in color, cloudy, having a pronounced acrid after-taste, easily becomes rancid, and congeals at a point lower than that given below, is inferior in quality and should have no place in medicine. The U. S. P. describes the best oil as follows: "A pale-yellow, or light greenish-yellow, oily liquid, having a slight, peculiar odor, and a nutty, oleaginous taste, with a faintly acrid after-taste. Specific gravity, 0.915 to 0.918 at 15° C. (59° F.). Very sparingly soluble in alcohol, but readily soluble in ether, chloroform, or carbon disulphide. When cooled to about 10° C. (50° F.), the oil begins to become somewhat cloudy from the separation of crystalline particles, and at 0° C. (32° F.) it forms a whitish, granular mass"—(U. S. P.). Olive oil is little soluble in alcohol if free from uncombined oleic acid. It is soluble in petroleum benzin and benzol, and in 5 parts of acetic ether. If exposed to light and air, olive oil becomes rancid and liberates oleic acid. Olive oil is the type of nondrying oils, and is therefore much used as a lubricant, although its tendency to become rancid prevents its unrestricted application for this purpose. Pure olive oil is also characterized by giving the elaïdin reaction (see Tests below).
Chemical Composition.—Olive oil may be differentiated by cold and pressure into about 30 per cent of a solid "fat, chiefly consisting of palmitin, stearin, and a small amount of arachin, the glyceride of arachic acid ([C20H40O2], a constituent of earthnut oil), and about 70 per cent of a fluid oil composed of olein with about 7 per cent of linolein (the glyceride of linoleic acid; see Oleum Lini). Rancid olive oil may contain from 2 to 24 per cent of free oleic acid. Chlorophyll and small amounts of the alcohol cholesterin (C26H43.OH) likewise occur in olive oil. Olive oil is frequently adulterated, being substituted, wholly or in part, by cotton-seed oil, earthnut oil, poppy, rape-seed, sesame, and lard oil. Its physical and chemical characteristics, such as specific gravity, point of congelation, saponification equivalent, its non-drying quality, the elaïdin test, its low iodine number, resulting from its limited power to absorb iodine, and other tests, assist in detecting adulterations.
Tests.—The U. S. P. gives the following tests for the purity of olive oil: "If 10 Cc. of the oil be shaken frequently, during 2 hours, with a freshly prepared solution of 1 Gm. of mercury in 3 Cc. of nitric acid, a perfectly solid mass of a pale straw-color will be obtained. If 6 Gm. of the oil be thoroughly shaken, in a test-tube, for about 2 minutes, with a mixture of 1.5 Gm. of nitric acid and 0.5 Gm. of water, then heated in a bath of boiling water for not more than 15 minutes, the oil should retain a light-yellow color, not becoming orange or reddish-brown, and, after standing at the ordinary temperature for about 12 hours, it should form a perfectly solid, light-yellowish mass (absence of appreciable quantities of cotton-seed oil, and most other seed oils). If 5 Cc. of the oil be thoroughly shaken, in a test-tube, with 5 Cc. of an alcoholic solution of silver nitrate (prepared by dissolving 0.1 Gm. of silver nitrate in 10 Cc. of deodorized alcohol, and adding 2 drops of nitric acid), and the mixture be heated for about 5 minutes in a water-bath, the oil should retain its original, pale-yellow color, not becoming reddish or brown, nor should any dark color be produced, at the line of contact of the two liquids (absence of more than about 5 per cent of cotton-seed oil, and of many other foreign oils). If 30 Cc. of the oil be saponified by heating with 20 Cc. of alcohol and 5 Gm. of potassa, the liquid then diluted with 200 Cc. of water, and freed from alcohol by boiling, on supersaturating the solution with diluted sulphuric acid, the fatty acids will form a layer on the surface. If these be separated as far as possible, free from water, and filtered, 5 Cc. of the filtrate, when shaken in a test-tube with 5 Cc. of concentrated hydrochloric acid, should not color the latter green; and, on the subsequent addition of about 0.5 Gm. of sugar, and again shaking the mixture, no violet or crimson tint should be produced in the acid layer within 15 minutes (absence of sesamum oil)"—(U. S. P.). (For the detection. of oil of sesame in olive oil, by a new color test, see J. F. Tocher, Amer. Jour. Pharm., 1891, p. 140. For details of analysis, we must refer the reader to special works, such as A. H. Allen's Commercial Organic Analysis, Vol. II, Part I, 3d ed., 1899, p. 126.)
Action, Medical Uses, and Dosage.—According to Mr. Sidney H. Maltass, a strong decoction of the leaves of the olive-tree, given in doses of a wineglassful every 3 hours, has cured the most obstinate and severe forms of intermittent fever. He considers it more effectual than quinine. Olive, or sweet oil, as it is often called, is emollient, nutritive, and aperient. A fluid ounce or two purges, but is uncertain and often ineffective; yet is very useful in teaspoonful doses for newly-born infants, where the mother's milk does not prove sufficiently laxative. As a demulcent, it is very useful in irritation of the mucous surfaces of the air passages, and of the alimentary tube. It may be given as a gentle aperient in cases where other agents would cause too much intestinal irritation; and is of service as an antidote to the strong alkalies, in which it acts by combining with them to form soap. It has been used in cases of poisoning by cantharides, but owing to its readily dissolving their active principle, it increases the peril of the patient. As an article of diet it is generally harmful to dyspeptics. Olive oil is largely used by workers in lead to prevent constipation and lead poisoning. Large doses, prepared in emulsion with egg and mint, have been successful in removing biliary concretions. It is said to be effectual in phthisis, particularly to control excessive sweating. Externally (with lime-water), it is a valued agent for anointing bruises, excoriations, superficial wounds, burns and scalds. It is a good application to the body outlets to prevent excoriation from acrid discharges. Olive oil is frequently used as a vehicle for anodynes and local anaesthetics, such as morphine, menthol, camphor, etc. An olive oil solution of camphor, applied warm, is very effective in mastitis. Olive oil relieves the various forms of earache. It removes rectal worms, and has a soothing effect upon the rectum in dysentery. Live insects in the ear may be destroyed and removed by filling the canal with the oil. Applied warm it gives relief to the bites and stings of insects. Rubbed over the whole surface of the body, it has been considered beneficial in the treatment of plague, scarlatina, and some other exanthematous affections. Finally, it is largely used as a lubricant for the operator's hands, and for specula, bougies, and other instruments to be introduced into the orifices of the body. To facilitate the passage of catheters, first introduce into the urethra a quantity of warm olive oil. Olive oil enters largely into the formation of liniments, cerates, ointments and plasters. The dose of olive oil ranges from 2 fluid drachms to 2 fluid ounces. In the countries where the olive grows the oil is used as a food.