TANNING MATTER. &C, 15 



III. 



A Third Scries of Experiments on an Artijicial Sub- 

 stance y zohich possesses the principal characteristic Pro- 

 perties of Tannin ; zcith some Remarks on Coed, By 

 Charles Hatchett, Esq, F,R.S,* 



I 



hi- 



N my former papers upon this subject, some account Experiments, 



has beeneiven of the effects produced by sulphuric acid f^S* °" f^ ^^^^' 



^ . ^ • 1 T 1 11 naal substance 



upon turpentine, resin, and camphor; and 1 shall now j^avingthecha- 



state the results of other experiments made with the same racter of tan- 

 acid upon a great number of the resins, balsams, gum re- ^^"^ ^^ 

 sins, and gums, the greater part of which, afforded that 

 modification of the artificial tanning substance, which for 

 the sake bf distinction, I have in the preceding papers de- 

 nominated the third variety. 



The process was simple digestion in sulphuric acid, 

 after which, the residuum was well edulcorated, and was 

 then digested into alcohol. This was separated by distil- 

 lation, the dry substance which remained was infused in 

 cold distilled water, and the portion dissolved, was exr 

 amined by solution of isinglass, muriate of tin, acetite of 

 lead, and sulphate of iron. 



Much sulphureous acid, carbonic acid, several of the 

 vegetable acids, particularly benzoic acid, (when the bal- 

 sams were employed,) and apparently water, were pro- 

 duced during the operation ; but in this paper I shall only 

 notice two of the products, namely, the tanning substance 

 and the coal. 



The sulphuric acid almost immediately dissolved the 

 ^resins, and formed transparent brown solutions, which 

 ])rogressIvely became black. 



The same effect was produced on most of the other sub- 

 stances, but the solutions of the balsams and of guaia- 

 cum were at first of a deep crimsop, slightly inclining to 

 brown. 



Caoutchouc and elastic bitumen were not dissolved, 



* Philos. Trans, i8o6. For the former papers see our Journal. 



but 



