0(52 EXPERIMENTS ON ASTRINGENT VEGETABLES, 



alkali. The infufion ftrongly reddened paper tinged with 

 liUpus. It was femitranfparent, and of a yellowifh-brown co- 

 lour. Its tafte was highly aftringent. 

 Sulph. acid pre- When fulphuric acid was poured into the infufion, a denfe 

 cipicates the fo- w j,i^jj, precipitate was produced ; and this effect was conftant, 

 whatever quantity of the acid was ufed. The refidual liquor, 

 when paffed through the filtre, was found of a (hade of colour 

 deeper than before. It precipitated gelatine, and gave a dark 

 colour with the oxygenated fulphate of iron. 

 This precip. The folid matter remaining on the filtre, flightly reddened 



feemed to be the vegetable blues; and, when diflblved in warm water, copioufly 

 and gallic acid precipitated the folutions of ifinglafs. M. Prouft,* who firft 

 and fome p a j c [ attention to its properties, fuppofes that it is a compound 



of the acid with tannin : but I fufpect that it alfo contains 

 gallic acid, and probably a fmall portion of extractive matter. 

 This laft fubftance, as is well known, is thrown down from its 

 folutions by fulphuric acid ; and I found, in diftilling the pre- 

 cipitate from galls by fulphuric acid, at a heat above 21 2 Q , that 

 a fluid came over, of a light yellow colour, which was ren- 

 dered black by oxygenated fulphate of iron ; but which was 

 not altered by gelatine. 

 Muriatic acid Muriatic acid produced, in the infufion, effects analogous to 



thiewdowna ^ (_ no f e produced by fulphuric acid ; and two compounds of the 

 ancfac'id, and a acid and the vegetable fubfrances were formed: the one united 

 fimilar com- to exce fs of acid, which remained in folution ; the other con- 

 excels of acid taining a confiderable quantity of tannin, which was precipi- 

 contmued dif- tated in the folid form. 



folved * ., When concentrated nitric acid was made to acl upon the 



N'tric acid . . . ... - . r .. , . , 



deftroyed both infufion, it was rendered turbid ; but the lolid matter formed 



principles and was immediately diffolved with effervelcence, and the liquor 



exZTcl. 2 m ° ^en became clear, and of an orange colour. On examining 



it, it was found that both the tannin and the gallic acid were 



deftroyed ; for it gave no precipitate, either with gelatine or 



the falts of iron, even after the refidual nitric acid was fatu- 



rated by an alkali. By evaporation of a portion of the fluid, 



a foft fubitance was obtained, of a yellowifh brown colour, 



and of a flightly fourifh tafie. It was foluble in water, and 



precipitated the nitro-muriate of tin, and the nitrate of alu- 



* The faft of the precipitation of folution of galls by acids, was 

 noticed by M. Dize. Ste Annates de C/jimie, Tome XXXV. p. 37. 



1 mine ; 



