TANNINE MATTER, &C. 2f " 



precipitate was obtained, but after each precipitation, a . 



- I'u lixpenmcnts, 



portion always remained dissolved by the water, whicn ^^^ ^^ ^^ .^^^^, 



acted upon the different reagents in a manner similar to ficial substance 

 the solutions of vegetable extractive matter. The tlavour j.^^^'"/ ^f^ \^^, 

 was also bitter, and in some degree aromatic, so that the ning matter, 

 residua, whether obtained from pit-coal, from Cannel 

 coal, or from asphaltum, seemed to possess properties in- 

 termediate between those of resin, and those of the vege- 

 table extractive substance. They appeared, however, to 

 be removed only by a very few degrees from the tanning 

 substance; for if digested in a small quantity of nitric 

 acid, and subsequently evaporated, they were immedi- 

 ately converted into it ; or if digested with sulphuric acid, ^ 

 .they speedily became reduced to coal. 

 § IV. 



In the 5th Section of my second Paper, some remarks 

 were made on the decoctions, obtained from vegetable sub- 

 stances which had been previously roasted ; and although 

 (excepting one instance) these decoctions did not afford 

 any permanent precipitate with gelatine, yet I have there 

 stated, that I did not think it right to conclude, that, 

 , similar decoctions made under certain circumstances, 

 might not occasionally possess those properties which 

 characterize the tanning substances. Moreover I also 

 observed in the same paper, that all of those decoctions, 

 upon the addition of a small portion of nitric acid and 

 subsequent evaporation, became converted into that va- 

 riety of tanning matter which is produced by the action 

 of nitric acid upon carbonaceous substances. I have 

 since extended these experiments, and shall here give some 

 account of them. 



I. 



Two hundred grains of the fresh peels of horse ches- 

 nuts were digested for about 12 hours in three ounces of 

 distilled water. The liquor was of a pale brown, and 

 formed a slight pale brown precipitate when solution of 

 isinglass was added to it. 



2. 



Two hundred grains of the same peels were moderately 

 roasted, and being afterwards digested with three ounces 

 of water, formed a dark brown decoction, which was not 

 rendered turbid by gelatine. 



1 ' The 



