Page:Illustrations of Indian Botany, Vol. 1.djvu/241

Rh I am here again indebted to Mrs. Colonel Walker for my subjects of analysis, having very lately received splendid specimens of the barks of both trees, with their exudations concreted on them.

The exudation of Garcinia cambogia, as I am informed by Mrs. Walker, concretes slowly and imperfectly, so as to remain long viscid in the climate of Ceylon. The specimens sent to me, on arriving here, still continued soft enough to receive the impression of the fingers when squeezed between them. The exudation was chiefly in the form of long slender tears, of a clear lemon-yellow tint, without odour or taste, of a distinct resinous appearance, both externally and in their fracture, and wholly incapable of forming an emulsion when rubbed with the wet finger. These properties are alone sufficient to establish it as a substance altogether distinct from true Gamboge; and this distinction is still further shown by its chemical composition.

Suspecting that its softness was owing to the presence of volatile oil, I distilled 50 grains of it with water in an apparatus, in which it was easy to measure any fluid given off, to the fourth part of a grain ; and after repeated cohobation, there were obtained six grains of a lively yellow volatile oil, possessing a faintturpentine odour. From another portion, weighing 20 grains, the resin and volatile oil were removed conjunctly by sulphuric ether ; and then cold water took up a principle agreeing entirely with Arabin in its characters ; after which there was only left a little dark, brittle, fibrous matter, evidently from particles of the bark. The analysis gave the following results :

It is not a little remarkable that this exudation, evidently a true gum-resin, and containing, too, a considerable proportion of gum, is nevertheless not emulsive. The resin differs essentially from that of true Gamboge, being somewhat less soluble in ether or rectified spirit, and possessing a colour somewhat different both in tint and in intensity. Its colour is not orange, but rather lemon-yellow ; and its solution is so much less intense in tint than that of the resin of Siam or true Ceylon Gamboge, that the last two present an equal depth of shade when dissolved in ten times as much spirit as the other."

"Mr. Royle having expressed an opinion in his Illustrations of the Botany of the Himalayan mountains, that a kind of Gamboge may also be produced by another species of the natural family Guttiferœ, namely, the Xanthochymus pictorius* it seemed to me desirable to determine that point also by an analysis of its resinous exudation, which Mrs. Walker's specimens, have put it in my power to accomplish.

The exudation on the bark of this species is even, more different in appearance from true Gamboge, than that of the Garcinia cambogia. It forms small tears of a pale greyish-green colour, sometimes also pale yellowish-green ; and it is translucent like a resin. It does not form an emulsion at all when rubbed with the wet finger. It is pretty hard, and in cold weather pulverizable.

From the facility with which it softens when heated, it probably contains some volatile oil ; but my specimen could not afford me enough for ascertaining that point with care. For the same reason I could not attempt an exact quantitative analysis of its other component parts. But it is evidently a true gum resin, containing, however, less gum than that of the Hebradendron. Sulphuric ether removes a pale greenish-yellow resin, leaving an opaque glutinous mass, which is broken up and partially dissolved by cold water. The watery solution froths on agitation, and when evaporated leaves a viscous matter, evidently Arabin, or soluble gum. A small quantity of fibrous impurities and fleery particles remains unattacked by the ether and cold water. One grain and seven-tenths of the gum resin yielded 1.3 of resin, 0.3 of gum, and 0.2 of fibre, that is, 76.5, 17.6, and 5.9 per cent. This result seems to indicate the absence of


 * Illustrations, &c. p. 132, part iv,— 1834.