Mr. Hatchett on an artificial tanning Substance. 217 ' 
water, after which, the solution being examined by the re- 
agents which had been employed in the former experiments, 
was found to produce similar effects, excepting some diffe- 
rence in the colour of the precipitates. 
I next added some of the liquid to a solution of isinglass, 
and obtained a copious precipitate. Thus it is evident, that 
a tanning substance may be formed from animal as well as 
from vegetable and mineral coal ; and it is not a little curious, 
that this enables us to assert as a matter of fact, although not 
of economy, that one portion of the skin of an animal may be 
employed to convert the other into leather. 
In the course of these experiments, I also subjected coak to 
the action of nitric acid, and obtained a product which re- 
sembled that which had been afforded by pit-coal ; but in this 
case (as might be expected) there was not any appearance of 
the deep yellow substance which has so often been men- 
tioned. 
These experiments therefore prove, that a tanning substance 
may be artificially formed by exposing carbon to the action of 
nitric acid ; and it also appears, that this is best effected when 
the carbon is uncombined with any other substance excepting 
oxygen. The following experiments seem to corroborate this 
opinion. 
1 . A piece of Bovey coal , which had perfectly the appearance 
of half-charred wood, was reduced to powder, and was digested 
with nitric acid until the whole was dissolved. 
The colour of the solution was deep yellow ; and, by eva- 
poration, a yellow viscid mass was obtained, which was 
dissolved in distilled water. This solution was then examined 
by various re-agents, and particularly by gelatine, but not any 
mdcccv. F f 
