[896] Or 18 to 65 per cent., sp. gr. 0·915 to 0·995, according to Siebold (1877).
[897] Flora Sylvatica for Southern India, Madras, part 24 (1872), 255.
[898] It may be further distinguished from Wood Oil as well as from copaiba, if tested in the following simple manner:—Put into a tube 19 drops of bisulphide of carbon and one drop of the oleo-resin, and shake them together. Then add one drop of a mixture of equal parts of strong sulphuric and nitric (1·42) acids. After a little agitation the appearance of the respective mixtures will be as follows:—
Copaiba—Colour faint reddish-brown, with deposit of resin on sides of tube.
Wood Oil—Colour intense purplish-red, becoming violet after some minutes.
Oleo-resin of Hardwickia—No perceptible alteration; the mixture pale greenish yellow.
By this test the presence in copaiba of one-eighth of its volume of Wood Oil may be easily shown.
[899] Beddome, op. cit.
[900] See also Hazlett, Madras Monthly Journ. of Med. Science, June 1872.
[901] Figures in Guillemin and Perrottet Floræ Senegamb. tent. 1830, p. 246, tab. 56; also Bentley and Trimen, Med. Plants, part 17 (1877).