Hydrogenated Castor Oil, also known as castor wax, is derived from castor beans (Ricinus communis), which is typically a liquid at room temperature, that has been processed by adding hydrogen to make it more stable and raises its melting point so that it is a solid at room temperature. It is odorless and insoluble in water.

Historically, ancient Egyptians used castor oil as fuel for their lamps. Castor oil has also been used as a lubricant in machine and aircraft engines, and is added to certain paints, dyes and varnishes as well. Ingestion of pure castor oil works as a laxative to treat constipation.

Uses

Castor oil, once widely used as a domestic purgative, is now more restricted to hospital use for administration after food poisoning and as a preliminary to intestinal examination. Owing to the presence of ricin, the seeds have a much more violent action than the oil and are not used as a purgative in the West. Non-ionic surfactants (polyethoxylated castor oils) of variable composition are produced by the reaction of castor oil with ethylene oxide and are used in certain intravenous preparations which contain drugs with low aqueous solubility. The oil and its derivatives find many non-pharmaceutical uses including the manufacture of Turkey Red Oil, soaps, paints, varnishes, plasticizers and lubricants.

The following castor oil derivatives, described as pharmaceutical aids are included in the BP/EP:

Hydrogenated castor oil. A fine, almost white to pale yellow powder, practically insoluble in water, m.p. 83–88°C. It contains principally 12-hydroxystearic acid.

Polyoxyl castor oil. A clear yellow viscous liquid or semi-solid, freely soluble in water. Prepared by the reaction of castor oil with ethylene oxide.

Hydrogenated polyoxyl castor oil. Of variable consistency depending on the amount of ethylene oxide/mol.