Mr. Hatchett on an artificial tanning Substance. 213 
§ 11 . 
In the course of my experiments on lac, and on some of the 
resins, I had occasion to notice the powerful effects produced 
on them by nitric acid, and I have since observed, that by long 
digestion, almost every species of resin is dissolved, and is so 
completely changed, that water does not cause any precipi- 
tation, and that by evaporation a deep yellow viscid substance 
is obtained, which is equally soluble in water and in alcohol, 
so that the resinous characters are obliterated. 
When I afterwards had discovered a natural substance, 
which was composed partly of a. resin similar to that of recent 
vegetables, and partly of asphaltum,* I was induced to extend 
the experiments already mentioned to the bitumens, in the 
hope of obtaining some characteristic properties by which the 
probable original identity of these bodies with vegetable sub- 
stances might be farther corroborated. In this respect I 
succeeded, in some measure better than I expected ; but I 
observed a very material difference between the solutions of 
the resins and those of many of the bitumens, such, for in- 
stance, as asphaltum and jet. The first effect of nitric acid, 
during long digestion with these substances, was to form a 
very dark brown solution, whilst a deep yellow or orange 
coloured mass was separated, which by subsequent digestion 
in another portion of nitric acid was completely dissolved, and 
by evaporation was converted into a yellow viscid substance, 
equally soluble in water and in alcohol, so as to perfectly 
resemble that which by similar means had been obtained from 
the resins, excepting, that when burned, it emitted an odour 
somewhat resembling that of the fat oils. 
* Phil, Trans. 1804, p. 385. 
