This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The British Pharmacopoeia (1914) recognises any variety of South American copaiba containing about 45 per cent, of volatile oil, and therefore excludes thin Para varieties containing much over that proportion but admits varieties of the Maracaibo type. The drug is, however, not infrequently sophisticated to bring it within the official limits.
The following are the chief adulterants and the means of detecting them.
Fixed vegetable oils, such as castor oil, render the resin left after evaporation of the volatile oil (best at a temperature of about 120° to 130°) tough or pasty, whereas it is usually (in Maracaibo copaiba) hard and brittle. The presence of fixed oil can also be detected by the high ester value; copaiba resin consists almost entirely of resin-acids and has a very low ester value (seldom over 15; fixed oils about 190).
Volatile oils, such as turpentine, may often be detected by distilling off the volatile oil in a current of steam and determining its specific gravity (0.896 to 0.910), boiling-point (250° to 270°), and optical rotation ( - 7° to - 35°) (sp. gr. of turpentine 0.850 to 0.880; b.pt. 155° to 165°). The optical rotation is important; a dextrorotatory oil would indicate the presence of African copaibas (compare also the official tests for Oleum Copaibae).
Colophony may be added to thin copaibas without making them suspiciously viscous. Copaiba should form a transparent solution with one-third of its volume of solution of ammonia.
Five gm. of the copaiba boiled with 15 c.c. of 95 per cent, alcohol for one minute and cooled should not separate oily drops (of paraffin oil).
Gurjun balsam, an oleo-resin obtained by incision from the trunk of Dipterocarpus turbinatus (N.O. Dipterocarpeoe) and other species, large trees indigenous to eastern India and Burma, is used both as a medicine and for various technical purposes. It somewhat resembles copaiba in odour and taste, but is usually darker in colour and fluorescent. It contains from 40 to 80 per cent, of volatile oil together with neutral and acid resins and has therefore a composition analogous to that of copaiba. Its presence in copaiba may be recognised by adding 4 drops to a mixture of 5 c.c. of glacial acetic acid and 4 drops of nitric acid; a purple or reddish coloration indicates gurjun balsam. It may also be detected by dissolving 2 drops of the balsam in 20 drops of carbon disulphide and adding a drop of a freshly prepared and cooled mixture of nitric and sulphuric acids; if gurjun balsam is present a violet coloration will be produced, but it has been shown that a similar colour has been occasionally yielded by genuine balsams. A similar test may be applied to the volatile oil separated from the copaiba by steam distillation; not more than a faint violet colour should be produced.
Sophistication by mixing a cheap thin copaiba with a more valuable thick copaiba is difficult to detect.
The active principles of copaiba are absorbed into the blood, the volatile oil, at least, being excreted by the kidneys, bronchi, and skin; hence copaiba produces along the whole genito-urinary tract, as well as in the bronchi, a stimulant and disinfectant action, increasing the mucous secretion and exciting expectoration. It is now chiefly employed in inflammatory affections of the bladder and urethra, and occasionally in chronic bronchitis. The resin is inert or nearly so.