n6 Mr. Hatchett's Experiments on a Substance , 
be similar to that which has been cursorily mentioned in my 
first Paper, and which was obtained from many of the pit- 
coals and bitumens when treated with nitric acid. I have since 
paid more attention to this substance, during the following 
experiments : 
Kilkenny coal was digested with nitric acid, and progres- 
sively, although with difficulty, was converted into that 
variety of the tanning substance which has so often been 
mentioned. Similar experiments were made on the same sort 
of coal from Wales, which was given to me by my friend Mr. 
Tennant, as well as upon a coal sent to me by Professor 
Woodhouse, which was from Pensylvania, and is there called 
Leigh high coal. All of these were converted into the tan- 
ning substance, but they did not yield any product similar to 
that obtained from the elastic bitumen. 
The contrary however happened when the common pit- 
coal, or Cannel coal, or asphaltum, were employed. For when 
these were treated in the way which has been described, and 
when the digestion was not too long continued, then I ob- 
tained from 100 grains of each of the above substances (after 
the separation of the tanning matter ) a residuum 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 - - 37 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 pro- 
