on a Substance possessing the Properties 0/ Tannin. 291 
artificial tanning substance, deepens the colour, after which, the 
solution becomes turbid and deposits a brown magma. 
D. Five grains of the dry substance were dissolved in half 
an ounce of strong ammonia ; the whole was then evaporated 
to dryness, and being dissolved in water, was found not to 
precipitate gelatine, unless a small portion of muriatic acid was 
previously added. 
E. Another portion of the same substance which had been 
dissolved in ammonia was evaporated in a long necked matrass, 
and was kept in very hot sand during half an hour ; at first 
some ammonia arose, and afterwards a yellow liquor which 
had the odour of burned horn. The residuum was then ex- 
amined, and was found to be nearly insoluble in water, to which 
it only communicated a slight yellow tinge. 
F. It is remarkable, that the dry artificial tanning substance, 
although prepared from vegetable matter, should, when placed 
on a hot iron, emit an odour very analogous to burned animal 
substances, such as horn, feathers, &c. ; this I found also to be 
the case in the experiment which has been related, and I was 
desirous therefore to ascertain more accurately the effects of 
heat on this substance when distilled in close vessels. 
I took some very pure vegetable charcoal which had been 
exposed to a red heat in a retort for more than an hour, and 
by nitric acid converted it into the artificial tanning substance. 
Twenty grains of this, rendered as dry as possible, were 
put into a small glass retort, to which a proper apparatus ter- 
minating in a jar filled with quicksilver and inverted in a mer- 
curial trough was adapted. The retort was placed in a small 
furnace, and was gradually heated by a charcoal fire until the 
bulb became red hot. 
P p 2 
