§88 Mr. Hatchet’s Additional Experiments 
In addition to the above experiments may be added, that the 
solutions of the artificial tanning substance seem to be com- 
pletely imputrescible, neither do they ever become mouldy like 
the infusions of galls, sumach, catechu, &c. 
Having thus ascertained the very unchangeable nature of this 
substance, I made the following comparative experiments on 
galls, sumach, Pegu cutch, kascutti, common cutch, and oak 
bark. 
8. Twenty grains of powdered galls were dissolved in half 
an ounce of the strong nitric acid ; the solution was then evapo- 
rated to dryness, and the residuum dissolved in boiling water. 
This did not produce the smallest effect on dissolved gelatine. 
g. A strong infusion of galls evaporated to dryness, and 
treated as above, was totally deprived of the tanning property. 
10. Isinglass precipitated by the infusion of galls, was dis- 
solved in nitric acid, and examined as in experiment 4, but no 
trace of tannin could be discovered. 
11. Twenty grains of sumach were dissolved in half an ounce 
of the strong nitric acid, and treated as in experiment 8, after 
which it appeared that the tannin was destroyed. 
12. Twenty graints of Pegu cutch (which contains a consi- 
derable quantity of mucilage) were subjected to a similar 
process, by which much oxalic acid was obtained, but every 
vestige of tannin was obliterated. 
13. Twenty grains of the catechu called Kascutti afforded 
results similar to the above. 
14. Twenty grains of the common cutch or catechu being dis- 
solved in nitric acid, evaporated to dryness, dissolved in water, 
and examined by solution of isinglass, rendered the latter 
