Oleum Ricini, B.P. Castor Oil.

Botanical name: 

Related entries: Castor oil seeds

Castor oil is obtained by expression from the seeds of Ricinus communis, Linn. (N.O. Euphorbiaceae), a native of India, but now grown in all tropical and subtropical countries. It is also official in the U.S.P. The expression is largely carried out in Italy, Marseilles, London, and Hull; after expression, the oil is usually bleached by exposure to sunlight, or by chemical means. Castor oil occurs as a colourless or faintly yellow, almost odourless, viscid liquid, having a taste at first bland but subsequently acrid and nauseating. It is a fixed oil, which dries very slowly. Specific gravity, 0.958 (B.P., 0.950) to 0.970 (0.955 to 0.965 at 25°). Slightly dextrorotatory, about +4° 30'. Refractive index, 1.4790 to 1.4805. Solidifying point, -10° to -18°. Acidity, not over 1.5 per cent., expressed as oleic acid. Saponification value, 176 to 187. Iodine value, 83 to 89. Acetyl value, about 150. Unsaponifiable matter, 0.30 to 0.37 per cent. The most distinctive features of the oil are its high specific gravity, behaviour with solvents, its acetyl value, and its very high viscosity. These constants afford a ready means of identification and determination of purity. The specific gravity is the highest of any natural fatty oil. A lower figure than 0.958 would almost certainly indicate adulteration. The acetyl value furnishes probably the surest means of ascertaining the purity, its high figure distinguishing castor oil from all commonly occurring oils. On cooling the oil to 0° it becomes turbid with separation of crystalline flakes, and at about -18° it congeals to a yellowish mass.

Soluble in alcohol (1 in 3.5), absolute alcohol, ether, oil of turpentine, or glacial acetic acid; insoluble in petroleum ether.

Constituents.—The chief constituent of the oil is ricinolein, a mixture of the glycerides of ricinoleic and isoricinoleic acids; tristearin and the glyceride of dihydroxystearic acid are also present in small quantities. The oil contains no olein or palmitin. Ricinoleic acid, C18H33O3, is a viscid oil, and yields ricinelaidic acid, a crystalline body, when acted upon by nitrous acid; similarly, when castor oil is treated with nitrous acid, the ricinolein is converted into ricinelaidin.

Action and Uses.—Castor oil is a mild purgative, its action being exerted as a result of saponification in the small intestine with formation of alkali ricinoleate. It should not be saponified before administration, as it may then irritate the stomach and set up nausea and vomiting. This oil is the most valuable laxative available in medicine; its use is not followed by my tendency to constipation, and it is suitable for use in pregnancy, after parturition, in piles or anal fissure, and for children or delicate persons. It is often of service in acute diarrhoea, with the addition of 6 decimils (0.6 milliliters) (10 minims) of tincture of opium. Small repeated doses may be given in the intestinal colic of children. The oil is used as a rectal injection to remove impacted faeces (see Enema Olei Ricini), sometimes with olive oil: it is also added to spirituous hair lotions to prevent the drying effect of the alcohol. Castor oil is an excellent solvent of pure alkaloids, and such solutions of atropine, cocaine, physostigmine, etc., are used in ophthalmic surgery. It is also dropped into the eye to remove the after-irritation caused by the removal of foreign bodies. Castor oil is best administered in milk, or as Mistura Olei Ricini. Capsules are prepared containing 10 to 60 minims in each, The dose should be administered an hour before breakfast, on an empty stomach. Aromatic castor oil is an agreeable form for administration to children. So-called "castor oil powders" are usually preparations of magnesium ricinoleate. Risiccol is a fine, white, tasteless and nearly odourless powder, containing 48.6 per cent. of castor oil and 35.8 per cent. of mineral matter, the latter consisting chiefly of magnesia.

Dose.—4 to 30 mils (I to 8 fluid drachms).


Also: Lubricant Oil

Emulsio Olei Ricini Aromatici, B.P.C.—EMULSION OF AROMATIC CASTOR OIL. 3 in 10.
Dose.—30 to 60 mils (1 to 2 fluid ounces).
Enema Olei Ricini, B.P.C.—ENEMA OF CASTOR OIL. 1 in 10 (mucilage of starch).
This enema should be well shaken before use. It is used to assist evacuation of the bowel. The quantity of the mixture sufficient for one application is 300 to 600 mils (10 to 20 fluid ounces).
Enema Olei Ricini cum Sapone, B.P.C.—ENEMA OF CASTOR OIL WITH SOAP.
Castor oil, 10; soft soap, 5; water, warm, to 100. This enema should be well shaken before use. The quantity of the mixture sufficient for one enema is 300 to 600 mils (10 to 20 fluid ounces).
Mistura Olei Ricini, B.P.—CASTOR OIL MIXTURE. Syn.—Emulsio Olei Ricini Castor Oil Emulsion.
Castor Oil, 37.5; mucilage of gum acacia, 18.75; orange-flower water, 12.5; cinnamon water, 31.25. Place the mucilage in a mortar, and add gradually in alternate portions, with constant trituration, the oil and the previously mixed waters. The following has been suggested as a simpler method of preparing this mixture:—Triturate 8.5 of powdered gum acacia in a dry mortar with 37.5 of castor oil; then add all at once 12.5 of orange-flower water mixed with half its volume of distilled water, triturate until the oil has been emulsified, and add, in small portions, 31.25 of cinnamon water, and sufficient distilled water to make up to the required volume. This mixture affords a convenient means of administering castor oil either to children or adults. Two fluid ounces contain 6 fluid drachms of castor oil. Dose.—30 to 60 mils (1 to 2 fluid ounces),
Oleum Ricini Aromaticum, B.P.C.—AROMATIC CASTOR OIL.
Castor oil, flavoured with amyl acetate, gluside and alcohol. Specially suitable for administration to children. It may be given mixed with milk, or from a spoon previously moistened with water, Dose.—4 to 30 mils (1 to 8 fluid drachms).

The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.