Gurjunic acid, C₄₄H₆₈O₈ according to Werner, melts at 220° C., and concretes again at 180° C.; it begins to boil at 260° C., yet at the same time decomposition takes place. By assigning to this acid the formula C₄₄H₆₄O₅ + 3H₂O, which agrees well with Werner’s analytical results, we may regard it as a hydrate of abietinic acid, the chemical behaviour of which is perfectly analogous. Gurjunic acid is soluble in alcohol 0·838, but not in weak alcohol; it is dissolved also by ether, benzol, or sulphide of carbon (Werner).
In copaiba from Maracaibo, Strauss (1865) discovered Metacopaivic Acid which is probably identical with gurjunic; the former, however, fuses at 206° C.
The amorphous resin forming the chief bulk of the residue of the distillation of the balsam, has not yet been submitted to exact analysis. We find that after complete desiccation it is not soluble in absolute alcohol. A crystallized constituent of Gurjun, which we obtained from a balsam of unknown origin, has been shown[371] to answer to the formula C₂₈H₄₆O₂. Its crystals, belonging to the asymmetric system, melt at 126°-130°C.; they are entirely devoid of acid character. A comparative examination of the product of each of the above named species of Dipterocarpus would be highly desirable.
Commerce—Gurjun balsam is exported from Singapore, Moulmein, Akyab and the Malayan Peninsula, and is a common article of trade in Siam. It is likewise produced in Canara in Southern India. It is occasionally shipped to Europe. More than 2000 lb. were offered for sale in London under the name of East India Balsam Capivi, 4th October 1855; and in October 1858, a no less quantity than 45 casks appeared in the catalogue of a London drug-broker. It is now not unfrequent in the London drug sales.
Uses—In medicine it has hitherto been employed only as a substitute for copaiba, and chiefly in the hospitals of India.
In the East its great use is as a natural varnish, either alone or combined with pigments; and also as a substitute for tar as an application to the seams of boats, and for preserving timber from the attacks of the white ant. To the first application it is often made better appropriated[372] by boiling it, so that the essential oil is evaporated.
Wood Oil of China—The oleo-resin of Dipterocarpus must not be confounded with the so-called Wood Oil of China, which is of a totally different nature. The latter is a fatty oil expressed from the seeds of Aleurites cordata Müll. Arg. (Dryandra cordata Thunb. Elaeococca Vernicia Sprgl. Prodromus xv. part 2, p. 724), the well-known Tung tree of the Chinese. It is a large tree of the order Euphorbiaceæ, found in China and Japan. The oil is an article of enormous consumption among the Chinese, who use it in the caulking and painting of junks and boats, for preserving woodwork, varnishing furniture, and also in medicine. In the commercial reports of H.M. Consuls in China (No. 5, 1875, p. 3, 26) we find that this oil is largely exported from Hankow: 199·654 peculs in 1874, and forms an article of import at Ningpo: 15·123 peculs in 1874 (pecul = 133·33 lb. avoirdupois). It is, however, not shipped to foreign countries. The oil of the Tung tree is also extremely remarkable on account of its chemical properties as shown by Cloëz (1875-1877).
MALVACEÆ.
RADIX ALTHÆÆ
Marshmallow Root; F. Racine de Guimauve; G. Eibischwurzel.