22 TANNING MATTER, &C. 



S. 



Experiments, rr^. , 

 &c. on an arti The aboTC mentioned roasted peels, after the termina- 

 ficial substance (ion of the preceding experiment, were added to the rc- 

 racur'of^tau- >"ai"d<ir of the filtrated liquor. A quarter of an ounce 

 ning matter, of nitric acid was poured upon the whole, which was then 

 digested and evaporated to dryness. The mass was after- 

 wards infused in water, and a dark reddish-brown liquid 

 was obtained, which copiously precipitated solution of 

 isinglass. 



4. 

 Two hundred grains of horse chesnuts, from which the 

 peels employed in the former experiments had been taken, 

 were bruised, and were digested with three ounces of wa.^ 

 ter. The liquor was turbid, and of a pale red colour. 

 It was filtrated, and some solution of isinglass was added, 

 but without any efiect. 



5. 

 Two hundred grains of the same horse chesnuts were 

 moderately roasted, and being treated as abore described 

 with water, yielded a dark brown decoction which was 

 not rendered turbid by isinglass. 



6. 

 The horse chesnuts, which had been employed in the 

 preceding experiment with the remaining liquor, were di- 

 gested with a quarter of an ounce of nitric acid until the 

 whole was become dry. Water was then poured upon it, 

 was digested, and a dark brown liquid was formed, which 

 afforded a considerable precipitate by the addition of 

 solution of isinglass. 



From these experiments it appears, that the small por- 

 tion of tannin which the horse chesnut peels originally 

 contained, was destroyed by the process of roasting ; that 

 the brown decoction subsequently obtained from the 

 roasted peels and from the horse chesnuts, did not act 

 upon gelatine; but that these were speedily converted 

 into the artificial tanning substance, by the addition of a 

 small portion of nitric acid and subsequent evaporation' 



The first preparations of the artificial tanning substance 

 which have been mentioned in the former Papers, were 

 made from coal of different descriptions digested with ni- 

 tric acid, and as similar products have been obtained by 

 the same acid from various decoctions pf roasted vegeta- 

 ble 



