ARTIFICIAL TAN. 433 



i. tl was bitter and aflringenf, had the odour of carorael, 

 and tormed with water a dark-brown foiution. 



'2, This foiution produced very dark-brown precipitates 

 wiih fulphate of iron, acetite of lead, muriate of tin, and 

 iiitrate of lime. 



3. Gold was precipitated by it in the metallic ftate from 

 its foiution. 



4. By foiution of ifinglafs the whole was precipitated ; foSubftanceC 



that after four hours a colourlefs water only remained. 1!T.•^^'"^^1''^ 



■' _ _ precipitates gela- 



This precipitate was nearly black, and was infoluble in ten. , 

 boiling water : from whence, and its effeds on Ikin, it was 

 evidently a variety of tanning matter much refembling that 

 obtained from refinous bodies by fulphuric acid. 



But this fort of tan had lefs efFed on flun than that pro- ' 



cured from carbonaceous fubftances by nitric acid, and its 

 precipitate from gelaten was more flocculent and lefs te- 

 nacious. 



However, when a fmall quantity of nitric acid was added 

 to the foiution of the fubftance obtained from camphor, and 

 when the refiduum, after evaporation to drynefs, was dif. 

 folved in water, a reddifti-brown liquor was formed, which 

 a6led in every refpe<5t iimilar to the tanning fubftance ob- 

 tained from the varieties of coal by the nitric acid, 



• § VII. 



From the experiments related, it appears that three va- The three varl- 

 rielies of the tanning fubftance may be formed. edes of artificial 



1ft. That produced by nitric acid with any carbonaceous 

 fubftance, whether vegetable, animal, or mineral, 



2d. That formed by diftilling nitric acid from common 

 lefin, indigo, dragon's blood, and various other fubftances, 



3d. That which common refin, elemi, aftafuetida, cam- 

 phor, &c. yield to alcohol, after they have, been previoufly 

 <iligefled with fulphuric acid. 



On thefe produds the author makes the following remarks : Remarks oa 



The firft variety is the moft eatily formed. From fome ex-*^^°^* 

 perimenls made purpofely it appears, that, after making al- 

 lowance for a fmall quantity of moifture and of nitric acid re- 

 maining, 100 grains of vegetable charcoal yield 116 of the loo grains char- 

 dry tanning fubftance. • coal yield H 6 



Vol.XUL^Ja^vary, isoe, , D from '*""'"* "'*''''' 



