[ 32d ] 



LXr. Additional Erperimfints and R^ifi'arh dn an artijjciut 

 Substance ivJvch possesses the principal characteristic Pro- 

 perties of Tannin. By Charlhs Hatchett, £50. 

 'F, R. S* 



§!• 



VV HEN r had ascertained that carbonaceous substances, 

 whether vegetable, animal, or mineral, were capable of 

 being converted into a product, which, by its effects 011 

 earthy and metallic solutions, on dissolved gelatine, and on 

 skin, resembled the natural vegetable principle called tan- 

 nin, I was at first inclined to give it the name of artificial 

 or factitious tannin ; but some eminent chemists of this 

 country^, for whose opinions I have the highest respect, 

 corisidered this name as objectionable; for, although the 

 artificial substance resembles tannin in the particulars above 

 stated, yet in one character there appears to be a very con- 

 sider.ible difference, namely, the effect of nitric acid ; for 

 by this the artificial substance is produced, whilst the va- 

 rieties of natural tannin are destroyed. Such an objection, 

 sanctioned by such authority, induced me to alter the title 

 of my paper, and to expunge the word /fwjzm wherever it 

 had been applied to the artificial product. 



In order to satisfy myself more fully on this point, I 

 have, since the communication of my former paper, made 

 a few experiments on the comparative effects produced by 

 nitric acid on those substances which contain the most no- 

 table quantities of tannin; and of these I shall now give a 

 succinct account, and shall also cursorily notice other ex- 

 ~perimcnts in which a tanning substance has been produced, 

 imder circumstances different, in some measure, from those 

 which have been already described. 



§ IT. 



Although T cannot as yet assert that the artificial tanning 

 product is absolutely indestructible when repeatedly di- 

 stilled with different portions of nitric acid, yet the follow- 

 ing experiments will prove that the destructihility of it by 

 this method must at least be a work of considerable time 

 and difficulty. 



1. Twenty grains of this substance were dissolved in half 

 an ounce of strong nitric acid, the specific gravitv of which 

 was ) '40. The solution was then subjected to distillation 



* From the Transactions of the RoT/al Societij for 1805. 



until 



