Oleum Arachis. Br. Arachis Oil.

Related entry: Arachis

Arachis Oil is the oil expressed from the seeds of Arachis hypogaea. Linn.

Earthnut Oil, Groundnut Oil, Peanut Oil.

The oil consists of the glycerides of four different fatty acids. The chief of these is oleic acid, C18H34O2, with which are associated linoleic acid, C18H32O2, hypogaeic acid, C16H30O2, arachidic acid, C20H40O2, and lignoceric acid, C24H48O2. It should be obtained by expression without heat. It is usually of a pale yellowish or green color with a faint odor, and a more distinct taste of the nuts, although on rectification a nearly colorless and tasteless oil may be obtained. Upon exposure to the air the oil slowly thickens and becomes rancid. It is soluble in all proportions in ether, chloroform, and petroleum benzin, but insoluble in alcohol.

At 3.3° C. (38° F.) it thickens, solidifies at about -5° C. (23°F.), and at 326.6° C. (620° F.) is decomposed, giving out spontaneously inflammable vapors. Winter made experiments to ascertain how far it might be employed with advantage in pharmacy, and found that it answered well in the preparation of cerates and ointments, but would not serve as a substitute for olive oil in the preparation of lead plaster. (See Proc. A. Ph. A., 1897,179.) Its use is permitted, by the British Pharmacopoeia, in India, and in the Eastern, African, and Australasian Divisions of the Empire, for making the official Liniments, Ointments, Plasters, and Soaps for which Olive Oil is directed to be used. It is a non-drying oil, and therefore will not answer for painting; but it is enormously used for adulteration (particularly of French olive oils) and for various purposes in the arts, as for lubricating machinery, and in the manufacture of woollen cloths; in lamps it burns with a bright light. It saponifies slowly, but yields an excellent firm, white, and odorless soap.

The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.