t6 Experiments on a Substance ti'hich possesses 



stances (after the separation of the tanning matter) a resi- 

 duum as follows : 



From 100 grains of the common Newcastle coal 9 grains. 



From 100 grains of Cannel coal - - 36 grains. 



From 100 grains of pure asphaltum - - (J grains. 



The substances thus obtained were very similar in their 

 external characters, being of a pale brown, approaching to 

 Spanish snuff colour ; their internal fracture was dark brown, 

 with a considerable degree of resinous lustre. When exposed 

 to heat they did not easily melt, but as soon as inflamed 

 they emitted a resinous odour mixed with that of fat oil, 

 and produced a very light coal, much exceeding the bulk of 

 the original substance. 



Alcohol completely dissolved them, and if water in a large 

 proportion was' added to a saturated solution, a precipitate 

 was obtained ; but 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 rlavour was alo bitter, and 

 in some degree aromatic, so that the residua, whether ob- 

 tamed from pit-coal, from Cannel coal, or from asphaltum, 

 scerncd to possess properties intermediate between those of 

 resiti and those of the vegetable extractive substance. They 

 appeared, however, to be removed only by a verv 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 froui vegetable sub- 

 stances which had been previously roasted ; arrd although 

 (excepting one instance) these decoctions did not afiord any 

 permanent precipitate with gelatine, yet I have there stated, 

 that I did not think it right to corjcludc, that similar de- 

 coctions made under certain circumstances, might not oc- 

 iSasronally possess those properties which characterize the 

 tann-ing substances. Moreover I also observed in the same 

 Pfjper, that all of those decoctions, upon the addition of a 

 9 small 



I 



