A genus of apetalous euphorbiaceous plants. R. communis, the only species is the well-known castor-oil plant, indigenous in America and Asia. The height is from 4 to 14 feet; the leaves are alternate, peltate, palmately seven-lobed or nine-lobed; the flowers are monecious and apetalous. The fruit is a grooved, rather triangular tricoccous capsule, generally spinescent, with a single oval or elliptic seed enclosed in each cell. The embryo has foliaceous, heart-shaped cotyledons, is straight, white, and imbedded in an oily albumin, having a bland and slightly acrid taste. The seeds are chiefly used in the manufacture of oleum ricini, castor-oil. They are first crushed and freed from their coverings, then kiln-dried and subjected to powerful pressure. The oil is heated with water to remove albuminous matters. The yield is 38 to 45 per cent., by cold pressure 25 to 30 per cent. The oil prepared by the latter method requires no further purification. It is viscid, nearly transparent, pale greenish-yellow or almost colorless. The specific gravity varies between .950 and .960. The oil is partly soluble in petroleum benzine, but is more soluble in absolute alcohol, ether, and glacial acetic acid in all proportions. When fresh, it has a neutral reaction to test- paper, and is composed of several fats. The solid fatty acid is related to palmitic acid, the liquid one is ricinolcic acid. The acrid principle to which its purgative properties are due has not been isolated. Tuson claimed, in 1864, to have discovered an alkaloid, ricinin. The oil is used medicinally to overcome constipation or to cure diarrhea due to the presence of irritating substances. The dose for an adult is from half an ounce to an ounce. R., Olei, Mist. Dose 3 ss-ij.
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