which possesses the characteristic Properties of Tannin . 125 
moistened with nitric acid, and was gently heated and dried 
as before. Water being poured on it and digested, formed a 
brown solution, which copiously precipitated gelatine. 
6 . 
The whole of the artificial tanning substance was extracted 
by different portions of water, and the remainder of the bark 
thus exhausted, was again treated in the manner above de- 
scribed, and again afforded a considerable quantity of the 
tanning substance, so that these processes evidently might 
have been continued until the whole of the bark had been 
converted into it. 
This might also have been accomplished, if in the first 
instance, the exhausted bark had been converted into char- 
coal, and digested in nitric acid, as described in my first Paper; 
but then, the effects would have been more slowly produced, 
and much more nitric acid would have been consumed. I am 
now therefore fully convinced, not only by the results of the 
experiments related in this Paper, but also by many others 
which it would have been superfluous to have stated, that the 
most speedy and most economical of all the processes which 
I have described, is that of treating roasted vegetable sub- 
stances in the way which has been mentioned, and considering 
that all refuse vegetable matter may be thus converted into a 
tanning substance by means the most simple, and without 
any expensive apparatus, I cannot help entertaining much 
hope, that eventually this discovery will be productive of 
some real public advantage. 
