which possesses the characteristic Properties of Tannin. 117 
duced a very light coal, much exceeding the bulk of the ori- 
ginal substance. 
Alcohol completely dissolved them, and if water in a large 
proportion was added to a saturated solution, a precipitate 
was obtained, bu,t after each precipitation, a portion always 
remained dissolved by the water, which acted upon the dif- 
ferent reagents in a manner similar to the solutions of 
vegetable extractive matter. The flavour was also bitter, and 
in some degree aromatic, so that the residua, whether ob- 
tained from pit-coal, from Cannel coal, or from asphaltum, 
seemed to possess properties intermediate between those of 
resin, and those of the vegetable extractive substance. They 
appeared however, to be removed only by a very few degrees 
from the tanning substance ; for if digested in a small quan- 
tity of nitric acid, and subsequently evaporated, they were 
immediately 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 substances 
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 variety 
of tanning matter which is produced by the action of nitric 
