ON ARTIFICIAL TANNIN. 36< 



a yellow matter separated, which was much more abun- 

 dant than what remained in solution, and had no property, 

 that rendered it similar to resins. I obtained the same re- 

 sults with two varieties of pitcoal, yet I do not allow my- 

 self the least reflection on the labours of that celebrated 



English chemist; as I am too fully aware, (hat different Causes ofdif- 

 , , to,. . . /.,,i. ference in re- 



modes of operating, and the different varieties of the bodies suils 



examined, are so many causes, that may produce a varia- 

 tion in the results. I shall proceed therefore to relate my 

 own experiments, and deduce from them the conclusions, 

 that appear to me most natural. 



2. The pitcoal I used was perfectly pure. 100 parts Pitcoal used, 

 heated strongly in a platina crucible left 84 parts of coak. 



I digested 100 parts of this coal, finely powdered, in Treated with 

 600 parts of nitric acid at 44° [sp. gr. 1*425]. An effer- 

 vescence took place, with the evolution of nitrous vapour, 

 &c. When the action diminished I increased the heat; and 

 at the expiration of 24 hours I added 600 parts of nitric 

 acid, and heated to boiling, taking care to pour back into 

 the retort the acid that passed over into the receiver, fi- 

 nally, when the matter appeared to be thoroughly attacked, 

 I poured it out into a capsule, and evaporated gently to 

 dryness. The residuum weighed 170 parts, consequently 

 there was an increase of weight of seven tenths. The hot 

 water, with which I washed it repeatedly, acquired a red- 

 dish brown colour, and an acid astringent taste, from dis- 

 solving the tannin of Mr. Hatchctt. The yellow and little 

 soluble matter, which I shall designate by the letter A, was 

 not dissolved. 



Art. I. Examination of the tanning matter of Mr. 

 Hatchett. 

 3. I evaporated to dryness the washings of the pitcoal Examination of 

 treated by nitric acid (2), redissolved the residuum in a small tann a in l 

 quantity of water, and thus separated a little of the matter 

 A. The filtered liquor had an acid taste, with a little bit- 

 terness and astringency: it coagulated gelatine very well. 

 To separate the tanning substance in a state of purity, I 

 poured into it acetate of lead, till no more precipitate was 



thrown 



