vegetable substance from China. 43 
to the action of heat, gradually raised to redness, in a retort 
to which a proper apparatus was adopted for collecting the 
liquid and gaseous products. They afforded the following 
results. 
Grains. 
Water tainted by empyreumatic oil, and holding gallic 
acid in solution 5° 
Gaseous compounds of charcoal with oxygen and 
hydrogen - - - - - 10 
Charcoal remaining in the retort, and affording traces 
of minute quantities of lime 38 
98 
It appears from the foregoing experiments, that the sub- 
stance existing in the Chinese galls which has the power of 
forming an insoluble white precipitate with animal jelly, and 
which has a purely astringent flavour, is also perfectly solu- 
ble in alcohol ; hence it seems, that the assertion of many 
chemical writers concerning the insolubility of pure tannin in 
that menstruum is not correct. In this respect the tannin of 
the China galls resembles that obtained from catechu, the 
properties of which have been examined by Sir H. Davy,* 
and it is probable, that the tannin described by Bouillon la 
GRANGE-f as insoluble in alcohol, obtained from infusion of 
galls by carbonate of ammonia, was not pure. 
The want of extractive matter in the China galls, would 
probably render them very unfit for the purposes of tanning, 
and I do not find from Du Halde, that they are ever applied 
by the Chinese to that use. I found the leather produced by 
. * Phil. Trans. 1803. f Annales de Chimie, Vol. 5 5 . 
G 2 
