CASTOR OIL, a fixed oil obtained from the seeds of the C. 0. plant. In extracting time oil, the seeds are first bruised between heavy rollers, and then pressed in hempen bags under a hydraulic or screw press. The best variety of oil is thus obtained by press ure in the cold, and is known as C. 0.; but if the bruised and pressed seeds be afterwards steamed or heated, and again pressed, a second quality of oil is obtained, which is apt to become partially solid or frozen in cold weather. In either case the crude oil is heated with water to 212°, which coagulates, and separates the albumen and other impurities. Exposure to the sun's light bleaches the oil, and this process is resorted to oil the large scale. When pure and cold-drawn, C. 0. is of a light yellow color; but when of an inferior quality, it has a greenish, and occasionally a brownish tinge.. It is somewhat thick and viscid. Its specific gravity is high for an oil, being about 060 (water being taken as 1000). It is miscible with alcohol or spirits of wine and ether. Reduced to a temperature of 0° F., it does not become but exposed to the air, it very slowly becomes rancid, then dry and hard, and serves as a connecting link between the drying and non-drying oils. It has a nauseous smell, and an acrid, disagreeable, and sickening taste, which may be overcome by the addition of a little magnesia. The principal acid presentin it is ricinolic acid (110,C.,,II.,00, which is allied to oleic acid.
C. 0. is one of the most convenient and mildest of purgative medicines. Given in doses of one or two tea-spoonfuls, with a little peppermint-watcr, it forms a gentle laxa tive for habits easily acted on by medicine; while a dose of a table-spoonful, or a little more, will almost always succeed if it remains on the stomach. The only serious objections to the use of C. 0., are its disagreeable flavor, and the sickness often produced by it; some persons get over this difficulty by floating the oil in hot coffee, which is said to remove its nauseous quality.
The adulteration of C. 0. may be various. Several of the fixed oils, including lard, may be employed. The best test of its purity is its complete solubility in its own vol ume of absolute alcohol, which other fixed oils are not. Croton oil is occasionally
added to increase the purgative powers of the oil..
The CASTOlt OIL PLAIT (ricinus commnnis) is a native of the s. of Asia, but now naturalized in the s. of Europe, and in other warm regions of the globe. The genus ricinus belongs to the natural order euphorbiacece. It has panicled flowers, with 3 to 5 partite perianth; the fruit a tricoccous capsule,with one seed in each cell, the outside of the capsule generally covered with soft spines. The C. 0. plant is often cultivated in gardens in the middle and even in the northern parts of Europe, where it is only an annual, attaining a height of 3 to 10 feet, but highly ornamented by its stately growth, its large, broad, palmato-peltate, 7 to 9-fid leaves, # to 2 ft. in diameter, and its gener ally purplish hue. Its flowers are produced in long glaucous racemes. In warmer climates, it is perennial, and its stem becomes arborcsccnt, attaining even 30 ft. in height, with a corresponding thickness, so that ladders arc used for climbing it. Dif ferent species which have been described, are probably mere varieties. It was known to the ancients, and appears to have been valued by them. Its seeds have been found in Egyptian sarcophagi. From the resemblance of its seeds to an insect called riehZUR, it received that name from the Romans. The seeds are oval, and about four lines long. They are chiefly valued for the oil which they yield, on account of which the plant is cultivated in the Levant, Spain, Provence, the West Indies, Brazil, the United States of America, as far n. as New Jersey, and in other tropical and warm temperate countries.—Although C. 0. is chiefly used in medicine, it is not unfit for lamps and for oiling the wheels of machinery. The streets of Lima arc lighted and the machines used in the works of the sugar plantations of Peru are oiled with it. The appearance of the C. 0. plant obtained for it the name of Palma ehristi, by which it is still some times called. Its seeds were formerly known as semina cataputicemajoris.