KXPER1MSNTS ON ASTRINGENT VEGETABLES. £>65 



When the magnefia wasdiflblved in muriatic acid, abrownifti Muriatic folu* 

 and turbid fluid was obtained, which precipitated gelatine and '&>« of mag- 

 the oxygenated falts of iron. So that there is every reafon^to 

 believe, that the earth, in acting on the aftringent infufion, had 

 formed two combinations ; one containing chiefly gallic acid, 

 which was eafily foluble in water ; the other containing chiefly 

 tannin, which was very difficultly foluble. 



Alumine boiled with the infufion became yellowim-gray, Alumina 

 and gave a clear white fluid, which produced only a tinge of 

 light purple in the folutions of iron. When the earth * was 

 employed in very fmall quantity, however, it formed an info- 

 luble compound only with the tannin and the extract ; and the 

 refidual liquor was found to contain a gallate of alumine with 

 excels of acid. 



The oxides of tin and of zinc, obtained by nitric acid, were Effecl: of the 



boiled with feparate portions of the infufion for two hours. In J? 1 ?" °[ " J in . an * 

 r r zinc on the m- 



both cafes, a clear fluid, which appeared to be pure water, was fufion. They 



obtained ; and the oxides gained a tint of dull yellow. A part *? ' zed , the ■*■ 



r l r i !•«• i i • • • • i m, r , . »olved matter, 



of each ot them was dinolved in muriatic acid. The ioIution a nd a muriatic 



obtained was yellow : it copiouily precipitated gelatine; and folution of the 



gave a denfe black with the falts of iron. Mr. Prouft f, who c jpi t a t e^ ge kJjne 



firft obferved the action of oxide of tin upon aftringent infu- and g ave a black 



fions, fuppofes that portions of tannin and gallic acid are 



decompofed in the procefs, or converted, by the oxigen of 



the oxide, yito new fubftances. Thefe experiments do not, 



however, appear to confirm the fuppofition. 



M. Deyeux obferved, that a copious precipitation was The precipitate 



occafioned in infufion of galls, by folutions of the alkalis. by , alk * lis /»™ 



ta ' V J re ' & a,ls 1S n0t 



combined with carbonic acid. Mr. Prouft has fuppofed that pure tannin as 



the folid matter formed is pure tannin, Separated from its fo- ^ouftfuppofes; 



Jution by the ftfonger affinity of the alkali for water; and he 



recommends the procefs, as a method of obtaining tannin. 



In examining the precipitate obtained by carbonate of potaffi for it is not af- 



fully combined with carbonic acid, and ufed to faturation, I ''"J?? 1 *' "°f 

 •> * * well foluble in 



have not been able to recognize in it the properties which are cold water or 



ufuallv afcribed to tannin: it is not poflefled of the aftringent a, <; onoi * nor . 



n ,.., «• ri''A it'i -ij • iTi a " s on Ratine, 



tafte ; and it is but flightly foluble in cold water, or in alcohol. nor ta ns~ikins. 



# Mr. Fiedler, I believe, firft obferved the action of alumine upon 

 tannin. Van-Mons's Journal, Vol. I. p. 86. 

 f Annates de Gbimie, Toine XLII. p. C9. 



Itl 



