306 Mr. Hatchett's additional Experiments 
the artificial tanning matter, much resembling that which may 
be obtained from resinous bodies by means of sulphuric acid. 
But it must be observed, that this sort of tanning substance 
seems to act less powerfully on skin, than that which is pre- 
pared from carbonaceous substances by nitric acid, and the 
precipitate which the former produces with solution of gelatine 
is more flccculent and less tenacious, than that which in like 
manner is formed by the latter. 
It is however remarkable, that when a small quantity of 
nitric acid was added to the solution of the substance obtained 
from camphor, and when after evaporating it to dryness, the 
residuum was dissolved in water, a reddish brown liquid was 
formed, which acted in every respect similar to the tanning 
substance obtained from the varieties of coal by nitric acid. 
§ VII. 
From the experiments which have been related, it appears, 
that three varieties of the artificial tanning substance may be 
formed, viz. 
1st. That which is produced by the action of nitric acid upon 
any carbonaceous substance, whether vegetable, animal, or 
mineral. 
2dly. That, which is formed by distilling nitric acid from 
common resin, indigo, dragon's blood, and various other sub- 
stances ; and, 
3dly, That which is yielded to alcohol by common resin, 
elemi, asa foetida, camphor, &c. after these bodies have been 
for some time previously digested with sulphuric acid. 
Upon these three products I shall now make a few remarks* 
