which possesses the characteristic Properties of Tannin. 115 
long time in sulphuric acid ; and it is remarkable, that these 
substances, which in their external characters so much re- 
semble each other, should be similar in their habits when 
exposed to the effects of this acid ; for, unlike the resins and 
most of the other bodies which were subjected to the pre- 
ceding experiments, and which were almost immediately 
dissolved when the acid was poured upon them, these on the- 
contrary remained undissolved, and only became partially 
carbonized on their surfaces. Even nitric acid does not so 
rapidly effect a change in the elastic bitumen as it does when 
applied to the other bituminous substances. 
1. 
100 grains of pure soft elastic bitumen were digested during 
three weeks in one ounce of nitric acid, diluted with an equal 
quantity of water ; a tough and slightly elastic orange-coloured 
mass then remained. Another ounce of the acid, not diluted, 
was poured upon this mass, and the digestion was continued 
until the whole was evaporated. The residuum was tenacious, 
and of the colour above mentioned. Water partially dis- 
solved it, and formed a deep yellow liquid, which copiously 
precipitated gelatine, and possessed the other properties of 
the tanning substance which is produced from the resins, &c. 
by nitric acid. 
An orange-coloured mass still remained, which was speedily 
dissolved by alcohol, and was precipitated from it by a large 
addition of water. 
This substance in many of its properties resembled the 
resins, but in others, seemed to approach those which cha- 
racterize the vegetable extractive matter. It appeared to 
Q * 
