the characteristic Properties of Tannin. 101 



about an ounce of this submerged oak into shavings, and 

 digested them in water. A brown decoction was formed, 

 which with muriate of tin afforded a pale brown precipitate } 

 with acetite of lead, a precipitate of a deeper brown ; with 

 sulphate of iron, a copious brownish-black precipitate ', but 

 with solution of isinglass not any effect was produced. 



The tannin of this oak wood had therefore either been 

 separated by solution, or had been decomposed ; so that the 

 only substance which remained capable of being dissolved 

 by water was the extractive matter. This last, in the pre- 

 sent case, was most probably the original extractive matter 

 of the oak ; but in some other instances (such, for example, 

 as that which was found in the alder leaves contained in the 

 Iceland schistus*,) I am much inclined to believe that ari 

 extractive substance of a secondary formation, if I may be 

 permitted to employ such a term, is produced during the 

 process of carbonization. If a substance, therefore, so com- 

 pact and solid as oak timber can by long submersion be de- 

 prived of its tannin, it naturally follows that the same effect 

 must be more speedily produced by the action of water on 

 the smaller vegetable bodies, which present an extensive sur- 

 face J and also on porous and bibulous substances, such as 

 peat. 



But although peat, as I have already observed, does not 

 contain any tannin, yet the imperfect carbonization which 

 it has undergone renders it, like the roasted ligneous bodies, 

 peculiarly susceptible of being converted into the artificial 

 tanning substance when exposed to the action of nitric acid. 

 It would be useless to enter into a detail of the different ex- 

 periments which I have made upon it, as they were similar 

 to those already related; and I shall therefore only here state, 

 that when seven ounces of well dried peat had been twice 

 moistened, and digested with diluted nitric acid, (to the 

 amount of rather more thati two ounces,) and subsequently 

 dried, I obtained by water a solution of the artificial tanning 

 Bubstaftcc, which when evaporated to dryness weighed two 



» Phil. Trans, for 1801, p. 391. 



G 3 ounces. 



