COPAIBA

copaiba, or copaiva (from brazilian _cupauba_), an oleo-resin--sometimes termed a balsam--obtained from the trunk of the _copaifera lansdorfii_ (natural order leguminosae) and from other species of _copaifera_ found in the west indies and in the valley of the amazon. it is a somewhat viscous transparent liquid, occasionally fluorescent and of a light yellow to pale golden colour. the odour is aromatic and very characteristic, the taste acrid and bitter. it is insoluble in water, but soluble in absolute alcohol, ether and the fixed and volatile oils. its approximate composition is more than 50% of a volatile oil and less than 50% of a resin. the pharmacopoeias contain the oleo-resin itself, which is given in doses of from a half to one drachm, and the _oleum copaibae_, which is given in doses of from five to twenty minims, but which is inferior, as a medicinal agent, to the oleo-resin. copaiba shares the pharmacological characters of volatile oils generally. its distinctive features are its disagreeable taste and the unpleasant eructations to which it may give rise, its irritant action on the intestine in any but small doses, its irritant action on the skin, often giving rise to an erythematous eruption which may be mistaken for that of scarlet fever, and its exceptionally marked stimulant action on the kidneys. in large doses this last action may lead to renal inflammation. the resin is excreted in the urine and is continually mistaken for albumin since it is precipitated by nitric acid, but the precipitate is re-dissolved, unlike albumin, on heating. its nasty taste, its irritant action on the bowel, and its characteristic odour in the breath, prohibit its use--despite its other advantages--in all diseases but gonorrhoea. for this disease it is a valuable remedy, but it must not be administered until the acute symptoms have subsided, else it will often increase them. it is best given in cachets or in three times its own bulk of mucilage of acacia. various devices are adopted to disguise its odour in the breath. the clinical evidence clearly shows that none of the numerous vegetable rivals to copaiba is equal to it in therapeutic value. copal (mexican _copalli_, incense), a hard lustrous resin, varying in hue from an almost colourless transparent mass to a bright yellowish-brown, having a conchoidal fracture, and, when dissolved in alcohol, spirit of turpentine, or any other suitable menstruum, forming one of the most valuable varnishes. copal is obtained from a variety of sources; the term is not uniformly applied or restricted to the products of any particular region or series of plants, but is vaguely used for resins which, though very similar in their physical properties, differ somewhat in their constitution, and are altogether distinct as to their source. thus the resin obtained from _trachylobium hornemannianum_ is known in commerce as zanzibar copal, or gum anime. madagascar copal is the produce of _t. verrucosum_. from _guibourtia copallifera_ is obtained sierra leone copal, and another variety of the same resin is found in a fossil state on the west coast of africa, probably the produce of a tree now extinct. from brazil and other south american countries, again, copal is obtained which is yielded by _trachylobium martianum_, _hymenaea courbaril_, and various other species, while the dammar resins and the piney varnish of india are occasionally classed and spoken of as copal. of the varieties above enumerated by far the most important from a commercial point of view is the zanzibar or east african copal, yielded by _trachylobium hornemannianum_. the resin is found in two distinct conditions: (1) raw or recent, called by the inhabitants of the coast sandarusiza miti or chakazi, the latter name being corrupted by zanzibar traders into "jackass" copal; and (2) ripe or true copal, the sandarusi inti of the natives. the raw copal, which is obtained direct from the trees, or found at their roots or near the surface of the ground, is not regarded by the natives as of much value, and does not enter into european commerce. it is sent to india and china, where it is manufactured into a coarse kind of varnish. the true or fossil copal is found embedded in the earth over a wide belt of the mainland coast of zanzibar, on tracts where not a single tree is now visible. the copal is not found at a greater depth in the ground than 4 ft., and it is seldom the diggers go deeper than about 3 ft. it occurs in pieces varying from the size of small pebbles up to masses of several ounces in weight, and occasionally lumps weighing 4 or 5 lb have been obtained. after being freed from foreign matter, the resin is submitted to various chemical operations for the purpose of clearing the "goose-skin," the name given to the peculiar pitted-like surface possessed by fossil copal. the goose-skin was formerly supposed to be caused by the impression of the small stones and sand of the soil into which the soft resin fell in its raw condition; but it appears that the copal when first dug up presents no trace of the goose-skin, the subsequent appearance of which is due to oxidation or inter-molecular change.