COMPOSITION OF GAMBOGE. 
137 
almost complete opacity, and which possesses, in fine powder 
a lively gamboge-yellow hue.* It is remarkable that the 
very volatile fluid, sulphuric ether, adheres with great force 
to this resin, insomuch as to be the source of much trouble, 
and even error, in a quantitive analysis. The vapour bath 
heat of 212° F. I found insufficient to drive off so much ether 
as to leave the resin firm when cold ; even at the temperature 
of 270°, maintained by means of a muriate of lime bath for 
six hours, so large a quantity was retained, that the detached 
principles almost always weighed conjunctly three per cent, 
more than the crude subject of analysis; nay, a heat of 400°, 
subsequently applied for four hours by an oil bath, which I 
considered the highest temperature to be safely applied to the 
resin, and which sent ofi* copious bubbles of ethereal vapour, 
still left a slight surplus of weight in the separated principles 
when summed up. 
" The ether leaves, in the case of Pipe Gamboge, a flocculent 
matter, which, when thoroughly exhausted by the repeated 
action of the same fluid, coheres somewhat and acquires a very 
pale yellowish-white colour. In fine specimens of this gam- 
boge, I have always found the flocculent residuum to be 
composed entirely of gum, presenting the leading characters 
of the prototype of the gummy principle named Arahin^ 
from is forming almost the entire mass of gum Arabic. It is 
entirely and easible soluble in cold water, forming a pale 
yellowish solution, which, when concentrated, becomes 
viscous, and when dried, forms a transparent, reddish sub- 
stance, of a mucilaginous taste with acridity. Braconnot 
thought the gum analogous to that of the plum tree; which, 
however, contains a considerable portion of the insoluble 
variety of gum named Cerosin, a variety entirely absent in 
Pipe Gamboge. 
" The proportions of the two principles vary somewhat, as 
will appear from the following results of trials made with one 
* Its colour is so intense that it connnciunicates an appreciable yellow- 
ness to ten thousand times its weight of spirit. 
VOL. III. NO. II, 18 
