SECT. IX. TANNIN. 40$ 



in astringent plants. It is obtained from the root 

 of the Walnut-tree, and rind of the Walnut ; as 

 also from the Sumac and Elder, but chiefly from 

 Nut-galls ; which are excrescences formed upon 

 the leaves of a species of Quercus indigenous ta 

 the South of Europe, in consequence of the punc- 

 ture of insects. The best in quality are brought 

 from the Levant. They are sharp and bitter to 

 the taste, and extremely astringent ; and soluble in 

 water by decoction when ground or grated to a 

 powder. The decoction strikes, with the solution 

 of iron, a deep black that forms the basis of ink, 

 and of most dark colours used in dyeing cloths. 



SECTION IX, 



Tannin. 



IF a quantity of pounded Nut-galls, or bruised HOW ob- 

 seeds of the Grape, is taken and dissolved in cold tam * 

 water, and the solution evaporated to dryness, 

 there will be left behind a brittle and yellowish 

 substance of a highly astringent taste, which sub- 

 stance is tannin, or the tanning principle. 



It is soluble both in water and alcohol, but in- Properties. 

 soluble in ether. With the salts of iron it strikes 

 a black. And when a solution of gelatine is mixed 

 with an aqueous solution of tannin, the tannin and 

 gelatine fall down in combination, and form an in- 

 soluble precipitate. 



