122 Mr. Hatchett’s Experiments on a Substance, 
The third experiment appears to shew, that a small quan- 
tity of a substance approaching to tannin was produced by 
the simple process of roasting ; and the fourth experiment 
corroborates those already described, in which, the artificial 
tanning matter was copiously produced, whenever roasted 
vegetable substances were treated with nitric acid. 
In respect to vegetable substances, especially those which 
contain tannin, I shall here relate a few other experiments. 
It has been remarked in my second Paper, (p. 288,) that 
the tannin of galls was immediately destroyed by nitric acid. 
Since that time, I have made the following additional ex- 
periments : 
1. 
100 grains of galls reduced to powder were infused with 
four ounces of water, and part of the infusion upon the addi- 
tion of solution of isinglass afforded (as usual) a copious 
precipitate of a brownish-white colour. 
A quarter of an ounce of nitric acid was added to one ounce 
of the above infusion, which then, was not in any manner 
affected by the dissolved isinglass. 
2. 
100 grains of the same galls were slightly roasted, and 
being digested with four ounces of water, formed a brown 
liquor, which was filtrated. 
Solution of isinglass was then added to a part of the above 
liquor, and produced a precipitate not very unlike the former, 
but much less in quantity. 
After this, a quarter of an ounce of nitric acid was added to 
one ounce of the same liquor, and some dissolved isinglass 
