Copal.
Synonyms.—Zanzibar Copal; Gum Animi.
Copal or gum animi is a fossil resin obtained from Trachylobium Hornemannianum, Hayne (N.O. Leguminosae), and found on the east coast of Africa. It is dug up by the natives and brought to Zanzibar, where it is prepared for the market by cleaning it from the dirt with which it is encrusted. Copal occurs in pieces of very varying size and of pale yellow to deep reddish-brown or greenish-red colour. It is usually transparent or semi-transparent, the surface being warty, or longitudinally striated or smooth. It consists chiefly of trachylolic acid (80 per cent.), associated with isotrachylolic acid (4 per cent.), and copal resenes (6 per cent.), together with volatile oil, bitter principle, etc. Specific gravity about 1.06. The term copal has been applied to a number of different resins, chiefly of fossil, but partly of recent, origin. They are the produce of very different plants, and have been obtained from different parts of the world. The chief and most important is Zanzibar copal, as described above. American copal, imported from Brazil and obtained from Hymenaea Courbaril, Linn., is pale brown, transparent, brittle, and of agreeable odour. Specific gravity, 1.028 to 1.082. Australian copal, or gum kauri, is obtained from Agathis Australis, Steud., a tree growing in the north of New Zealand. The greater part of the exported resin is fossil, and occurs in large pieces, of a pale yellow or greenish-yellow colour, with a conchoidal vitreous fracture and a balsamic odour. Specific gravity, 1.062 to 1.109, or even higher. The finer specimens are occasionally used as amber substitutes. East Indian dammar is sometimes called Manilla copal (see Dammar). West African copal is obtained from Copaifera Guibourtiana, Benth.
Entirely soluble in alcohol, but only partially in benzol, chloroform, glacial acetic acid, or ether.
Uses.—Zanzibar copal is used principally in the manufacture of varnishes. For this purpose it is heated until frothing ceases, when linseed oil is added and the mixture again heated to about 260°, the thick liquid so produced being dissolved in oil of turpentine. Under the name Gum Animi, it is occasionally ordered as an ingredient of plasters.
