ARTIFICIAL XAN. gj 



8. Twenty grains of powdered galls were difToIved in half Experiments on 

 an ounce of ftrong nitric acid : The refiduum from this foiu-^^^'^^l^ kTfcmi 

 tion evaporated todrynefs, and then dilToIved in boiling water, Pegu cutch, aa4 

 did not produce the fmallefl effeQ on diflblved gelatine. °^^ ^^^^' 



The experiments on to No. 13. did not produce any tannin. 



9. The refiduum of a ftrong infufion of galls, treated as 

 No. 8. 



10. Ifinglafs precipitated by infufion of galls, dinblved in 

 firong nitric acid, and examined as No. 4. 



1 1. Twenty grains of fumach diiTolved in half an ounce of 

 ftrong nitric acid, and treated as No. 8. 



12. Twenty grains of Pegu cutch (which contains much 

 mucilage) fubjedled to a firailar procef<, by which much oxalic 

 acid was obtained. 



13. Twenty grains of catechu, called kafcatli, treated fimi- 

 larly, had, together willi the four foregoing experiments, 

 all the fame refults as No. 8, not any of ihem fliewing any 

 tannin. 



14". Twenty grains of common catechu, difiolved in firong 

 nitric acid, evaporated to drynefs, diffolved in water, and 

 examined by ifinglafs, depofited a tenacious film infoluble 

 in boiling water, evidently compofed of gelatine and tannin. 



15. Twenty grains of oak bark treated in the fame way, 

 depofited alfo an infoluble film on the fides and bottom of the 

 vefiel. 



16. Infufions of galls, fumach, and oak wood, of equal 

 ftrength, were mixed with nitric acid, in the proportion of 

 half an ounce meafure of each to one drachm of the acid, and, 

 did not then render ifinglafs folution turbid. 



But infufions prepared from oak bark and the artificial tan, 

 and managed in the fame way, continued to precipitate the 

 gelatine, until four drachms of the nitric acid had been added 

 to each half ounce of the infufion. 



Thefe refults ihew that artificial tan is the moft indeftruc- 

 tible, but that the other tanning fubflances have confiderable 

 varieties in this refped. The tannin of oak bark refifts nitric 

 acid longer than that of galls, fumach, kafcutti, or Pegu 

 cutch. , This laft is replete with mucilage, and yields much 

 oxalic acid, as before defcribed : it feems alfo to be the moft 

 deftru6iible of all the kinds of catechu : from thefe fads the 

 SBthor was induced to gdd the fggftr and gum to the artificial 



tan. 



