74 .Experitnenfs on a Sulsiance which possesses 



tity of a substance 2j)proach?ng to tannin was produced hy 

 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, that the 

 tannin of galls was immediatelv destroyed by nitric acid. 

 Since that time, I have made the following additioiial ex- 

 periments : 



1. 100 grains of galls reduced to |>owder were infused 

 with four ounces of water, and part of the infusion upon the 

 addition of solution of isinglass afforded (as usual) a copious- 

 pvecipiiate of a brownish-white colour. 



A quarter of an ounce of nitric acid was added to onf 

 ounce of the above infusion, which then was not in anj. 

 manner affected by the dissolved isinglass. 



2. 100 grains of the same galls were slightly roasted, and 

 be-ing dijiested with four ounces of water, formed a browB 

 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 isin- 

 glass was subsequently poured into it ; by which it was ren- 

 dered tnrbid, and a small portion of a daifk brown precipi- 

 tate was produced, resembling that which is commonly 

 afforded by the artificial tanning substance, 



3. The remainder of the above-mentioned liquor, witVj 

 the residuum of the roasted galls, were digested with a 

 quarter of an ounce of nitric acid until the whole had be- 

 come di V. Water was then poured upon it, and formed a 

 dark brown solution, which yielded a copious brown preci- 

 pitate by the addition of dii^solved isinglass. 



From thc-e experiments on galls it appears, that the natu- 

 ral tannin contained in them isi destroyed .by nitric acid ; 



th*t 



