gij^ ARTrrrcrAL taw. 



Carbon th: btfe From the manner in wliicli it is produced, carbon is evl-* 



of the tanning dently the bafe and predominating eflfential ingredient in this 

 matter. c \ n 



rubftance. 



It alfo contains From § III. experiment F^ it alfo appears that the other 

 oxigen, hidro- component parts are oxigen, hidrogen, and nitrojren; for 

 gen, andnuro- , ,, -^ . , ,.„,, , . , , • 



•en. when (he artincial tan was dirrilled, ammonia and carbonic 



aeid were obtained,, excIufiA^e of a fmall portion of a yellow 



li^quor that appeared to be of arr oily iwture, from being in- 



foluble in water and alcohol. 



Many of the properties of the tanning fubftance prepared 



from coal by nitric acid are very remarkable, particularly 

 It Bss an odour thofe noticed in §111. experiment F ; of its having the odour 

 likeamma mat- ^p^^^j^^^^l fubftances when burned, though prepared from ve- 

 ed, and one of getable matter ; and in experiment G, of the precipitate 



oakbarkwhea havine; the odour of oak bark, though the component mate- 

 precipitated as ° . ' o t 



in G, § III. fials were inodorous. 



It refembles ve- Bat its moft extraordinary properties are thofe in which ifc 



g«:table tannin f^ nearly approaches the vegetable tannin, which it perfeflly 



tics. refembles in its folubility in water and in alcohol, in its aflion 



on gelaten and on ik'm, in its efFedls on the metallic iblutions^ 



on the alkalis, and on the earths. 



The fulphuric and muriatic acids alfo afTefl: its folutions, a» 

 Difference be- they do thofe of tannin ;, and the only marked difference be- 

 tween It and tween artificial tan and tannin is, that the former is produced 

 by nitric acid, while the varieties of the latter are more or lef* 

 deflroyed by it ; but here it muft be remembered, that even 

 tlie varieties of tannin do not accord in the degree of de- 

 ftruaibiiitj. 

 Second variety The fecond fpecies of the tanning fuBfiance is obtained 

 of artificial tan. frorn a variety of vegetable bodies before recited, by digefi.* 

 ing and diftilling them with nitric acid. It is therefore notfo 

 rtadily prepared, and the quantity of it produced is lefs in 

 proportion to the fubftance from which it is prepared. 



As relin and fome other bodies do not afford it until they 



have been repeatedly treated with nitric acid, and as, during. 



each operation, nitrous gas is produced, while the ftrength 



Tlieory of Its of the aeid which comes over is diminithed, the author thinks- 



farmition, it almoft certain that the tanning fubftance is formed in confe- 



quence of part of the oxigen of the nitric acid becoming com- 



bitwd with the bidrogen of the original body, fo as to form 



5 water ; 



