Related entries: Olive leaves
Olive oil is obtained by expression from the ripe fruit of Olea europaea, Linn. (N.O. Oleaceae), a small tree cultivated in Spain, France, Italy, and other countries bordering on the Mediterranean, also in California and South Australia. It is also official in the U.S.P. Olive oil occurs as a pale yellow or greenish-yellow liquid, with a faint, peculiar odour, a nut-like taste, and a faintly acrid after-taste. Specific gravity, 0.914 to 0.919 (0.910 to 0.915 at 25°); saponification value, 185 to 196; iodine value, 79 to 88; unsaponifiable matter, 0.46 to 1.0 per cent.; solidifying point -6° to +2°. The green colouration of some oils is due to chlorophyll. Exposed to the air, the oil loses colour and becomes rancid, acquiring a disagreeable smell, sharp taste, and a thicker consistence, the changes being promoted by heat and accompanied by a large increase in the quantity of free fatty acid present in the oil. When heated to 120°, it becomes lighter in colour; at 220°, it becomes nearly colourless, and at the same time rancid; at 315°, it is decomposed. Olive oil may be adulterated with cotton-seed oil, earth-nut oil, sesame, poppy-seed, and other oils, all of which are less readily congealed than olive-oil. Oils of high specific gravity usually exhibit a dark colour. If the specific gravity of a pale oil be found higher than 0.917 it may be looked upon with suspicion as possibly adulterated with sesame, cotton-seed, or poppy-seed oils. Admixture with rape oil tends to lower the specific gravity. Since olive oil has a lower iodine value than any other oil that might be used as an adulterant, this figure constitutes a most valuable means of detecting adulteration, any admixture with poppy-seed oil and, to a lesser extent, with sesame, cotton-seed, and rape oils, distinctly increasing the iodine value. Any considerable addition of rape oil would lower the saponification value materially. If shaken vigorously with an equal volume of nitric acid (specific gravity, 1.370), olive oil should retain a light yellow colour, not becoming orange or reddish-brown, and, after standing for six hours, should change into a yellowish-white solid mass and an almost colourless liquid (absence of appreciable quantities of cotton-seed oil and most other seed oils). If 2 mils of the oil be mixed in a test-tube with 2 mils of equal volumes of amylic alcohol and carbon bisulphide containing 1 per cent. of sulphur in solution, and the test-tube be immersed in boiling water, no reddish colour should develop within a period of ten to fifteen minutes (absence of cotton-seed oil). If 2 mils of the oil be mixed with 1 mil of hydrochloric acid (specific gravity, 1.18) containing 1 per cent. of sugar, the mixture shaken for half a minute and allowed to stand for five minutes, then 3 mils of water added and the whole again shaken, the acid layer should not show a pink colour (absence of sesame oil). Good oil should not contain more than l per cent. of free acid, calculated as oleic acid.
Partially soluble in alcohol, soluble in ether (1 in 2), readily soluble in chloroform or carbon bisulphide.
Constituents.—The chief constituent of the oil is olein, the glyceride of oleic acid, which constitutes about 93 per cent. of the portion which remains liquid when cooled to very low temperatures; the remaining 7 per cent. consists partly of linolin, the glyceride of linolic acid. The oil contains no stearin. The part which congeals consists of palmitin and arachin, the glycerides of palmitic and arachidic acids, the arachin being present in very small proportion. Phytosterol and free fatty acid are also usually present in small quantity in the oil, the proportion of free acid being considerable in the case of inferior, old, or rancid oil.
Action and Uses.—Olive oil is nutritious, demulcent, and from its lubricating action on the bowels, mildly laxative. It has been recommended for use in place of cod-liver oil as a nutritive; it may be administered without preparation, or in a capsule, or in the form of emulsion. For gall-stones or as a laxative, 4 to 8 fluid ounces or more of olive oil are taken daily. It is administered freely as an antidote in poisoning by corrosive substances. Sterilised olive oil (Oleum Olivae Asepticum) is prepared by heating the oil for half an hour at 120° to 140°, in small flasks or bottles, the necks of which are tightly plugged with cotton wool. It is injected hypodermically as a nutrient in doses of 4 to 8 mils (1 to 2 fluid drachms). Externally, olive oil is emollient and soothing to inflamed surfaces; it may be applied freely to burns, alone or mixed with an equal quantity of lime water. It is applied to the skin to remove incrustations in eczema and psoriasis, and is used as a lubricant in massage. Large quantities (5 to 20 fluid ounces) are injected per rectum in constipation and to remove impacted faeces. Olive oil is largely employed in pharmacy, in the preparation of liniments, ointments, and plasters.
Dose.—15 to 30 mils (1/2 to 1 fluid ounce), or more.
- Emulsio Olei Olivae, B.P.C.—EMULSION OF OLIVE OIL. 1 in 8.
- Dose.—8 to 30 mils (2 to 8 fluid drachms).
- Emulsio Olei Olivae Composita, B.P.C.—COMPOUND EMULSION OF OLIVE OIL.
- Contains 50 per cent. of olive oil emulsified with yolk of egg and tragacanth, together with flavouring agents. Dose.—8 to 30 mils (2 to 8 fluid drachms).
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.