on a Substance possessing the Properties of Tannin. 287 
solution of the artificial tanning substance, and the precipitate 
having been well washed with hot distilled water, was after- 
wards gradually dried. It was then digested in strong nitric 
acid, which after some time acted powerfully upon it ; much 
nitrous gas was evolved, and a dark brown solution was 
formed. This was evaporated to dryness, and after having been 
completely dissolved in boiling distilled water, was examined 
by nitrate of lime, acetite of lead, muriate of tin, and solution 
of isinglass, all of which formed copious precipitates, similar 
in every respect to those produced by the artificial tanning 
substance, which had not been subjected to the above described 
process. 
5. A portion of the precipitate, formed by isinglass and the 
tanning substance, was dissolved in pure muriatic acid, and 
was afterwards evaporated to dryness. Boiling distilled water 
dissolved only a small part, and the solution, which was of a 
dark beer colour, did not precipitate gelatine, although it acted 
upon muriate of tin, and sulphate of iron ; for with the former 
it produced an ash-coloured precipitate, and with the latter a 
slight deposit of a reddish-brown colour. 
6. As so small a part of the precipitated isinglass had been 
thus rendered soluble in boiling water, the residuum was 
treated with nitric acid, as in experiment 4, after which, being 
evaporated to dryness, it was found to be completely soluble 
in water, and precipitated gelatine as copiously as at first. 
7. I dissolved 20 grains of the pure tanning substance in 
about half an ounce of muriatic acid ; but, after distillation to 
dryness, the residuum in every respect appeared to be un- 
changed. 
