286 Mr. Hatchett’s additional Experiments 
on those substances which contain the most notable quantities 
of tannin , and of these I shall now give a succinct account, and 
shall also cursorily notice other experiments, in which a tan- 
ning substance has been produced, under circumstances different, 
in some measure, from those which have been already described. 
§H. 
Although I cannot as yet assert, that the artificial tanning 
product is absolutely indestructible when repeatedly distilled 
with different portions of nitric acid, yet the following experi- 
ments will prove, that the destructibility of it by this method 
must at least be a work of considerable time and difficulty. 
1. Twenty grains of this substance were dissolved in half 
an ounce of strong nitric acid, the specific gravity of which 
was 1.40. The solution was then subjected to distillation until 
the whole of the acid had come over, after which, it was 
poured back upon the residuum, and the distillation was thus 
repeated three times. 
Care was taken not to overheat the residuum, and this, when 
examined, did not appear to have suffered alteration in any of 
its properties. 
2. Ten grains of the artificial tanning substance, mixed with 
ten grains of white sugar, were dissolved in half an ounce of 
nitric acid, and the whole was distilled to dryness. 
The residuum being then dissolved in boiling distilled water, 
and examined by solution cf gelatine and other reagents, was 
found to be unchanged in every respect. 
3. This resembled the former, only that gum arabic was 
employed in the place of sugar. The result was the same. 
4. A quantity of dissolved isinglass was precipitated by a 
