vegetable substance from China. 41 
carefully evaporated to dryness, there remained upon the 
glass capsule 75 grains of a brown transparent substance, 
having a resinous fracture, a rough, astringent, and slightly 
sour taste, and which powerfully reddened litmus paper. It 
was quite soluble in cold water, and the solution had the same 
properties as the former, except that its colour was somewhat 
deeper. It was perfectly soluble in alcohol, (sp. gr., 820 at 
6 o°), and its properties were not altered by repeated solution 
in water and evaporation. 
It appears from these characters, that the substance in 
question contains tannin nearly free from extractive matter. 
Indeed, I am not aware that tannin exists in the same state of 
purity in any other vegetable product. 
The residuum which had resisted the action of water weigh- 
ed when dry 27 grains ; it was digested in 2 ounces of alcohol, 
which acquired a slightly brown tint, and was rendered turbid 
by the addition of water. The substance that precipitated was 
fusible and inflammable, and had the other characters of 
resin. When heated it exhaled a very peculiar odour. There 
now remained 23 grains of a grey substance insoluble in 
boiling water and alcohol, and which when heated burned 
quietly away without residuum, and therefore possessed the 
characters of woody fibre, 
During the preceding experiments, several circumstances oc- 
curred, which induced me to believe, that the aqueous solution, 
though remarkably free from extractive matter, contained a 
considerable proportion of gallic acid, I therefore endeavoured 
to ascertain the relative quantity of this acid contained in the 
brown residuum obtained from the watery infusion. For this 
purpose it was boiled in water with carbonate of barytes, 
mdcccxvii. G 
