Olibanum is a gum-resin obtained from Boswellia Carterii, Birdwood (N.O. Burseraceae), and other species of Boswellia, small trees indigenous to Somaliland and Southern Arabia. The trees contain schizogenous ducts in the bark, in which an oleoresinous emulsion is secreted. The secretion exudes on incision, and, when it has sufficiently dried, is collected and exported from Aden via Bombay. Olibanum occurs in small tears, varying from 5 to 25 millimetres in length. They are usually ovoid in shape, and of a pale yellowish, bluish, or greenish colour. The surface is dusty, and dull after the removal of the dust. Internally, they are dull, waxy, and semi-translucent. The odour is agreeable, the taste is fragrant and slightly bitter; the tears easily break up when masticated, and soften to a plastic mass.
Constituents.—The gum-resin contains 60 to 70 per cent. of resin, 27 to 35 per cent. of gum, and 3 to 8 per cent. of volatile oil. The resin consists chiefly of a resin acid (boswellic acid) and a resene (olibanoresene) in about equal proportions; the gum consists chiefly .of arabin, with which a little bassorin is associated. The volatile oil (specific gravity, 0.875 to 0.885; optical rotation, -11° to -17°) is colourless or yellowish, and fragrant; it consists of l-pinene, dipentene, and phellandrene. The oxygenated constituents which ,distil above 175°, and probably contain the aromatic bodies, have not yet been investigated.
Action and Uses.—Olibanum is used in the preparation of plasters, and is an ingredient of incense and fumigating powders.