6s JExperirnerits and Ohserval'ions on the 



low 200", fifty-three grains of solid matter; which, as well 

 as I could estimate by the methods of analysis that have 

 been just described, consisted of about nine-tenths of tan- 

 nin, or matter precipitable by gelatine, and one-tenth of 

 gallic acid, united to a minute portion of extractive matter. 



100 grains of the solid matter obtained from the infusion 

 left, after incineration, nearly 4| grains of ashes ; which 

 were chieiiv calcareous matter, mixed with a small portion 

 of fixed alkali. The infusion strongly reddened paper tinged 

 with litmus. It was semitransparent, and of a yellowish- 

 brown colour. Its taste was highly astringent. 



When sulphuric acid was poured into the infusion a dense 

 whitish precipitate was produced ; and this effect was con- 

 stant, whatever quantity of the acid was used. The residual 

 liquor, when passed through the filter, was found of a shade 

 of colour deeper than before. It precipitated gelatine, and 

 gave a dark colour with the oxygenated sulphate of iron. 



The solid matter remaining on the filter slightly reddened 

 veoetable blues ; and, when dissolved in warm water, co- 

 piously precipitated the solutions of isinglass. M. Proust*, 

 who first paid attention to its properties, supposes that it is 

 a compound of the acid with tannin : but I suspect that it 

 also contains gallic acid, and probably a small portion of 

 extractive matter. This last substance, as is well known, 

 is thrown down from its solutions by sulphuric acid ; and 

 I found, in distilling the precipitate from galls by sulphuric 

 acid, at a heat above 212*^. that a fluid came over of a light- 

 vellow colour, which was rendered black by oxygenated 

 sulphate of iron, but which was not altered by gelatine. 



Muriatic acid produced, in the infusion, effects analogous 

 to those produced by sulphuric acid ; and two compounds 

 of the acid and the vegetable substances were formed : the 

 one united to excess of acid, which remained in solution ; 

 . the other containing a considerable quantity of tannin, 

 which was precipitated in the solid form. 



When concentrated nitric acid was made to act upon the 

 infusion, it was rendered turbid ; but the solid matter formed 

 was inmiediately dissolved with effervescence, and the liquor 

 then became clear, and of an orange colour. On examining 

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

 were destroyed ; for it gave no precipitate either with gela- 

 tine or the salts of iron, even after the residual nitric acid 

 was saturated by an alkali. By evaporation of a portion of 



'•■ The fact of the precipitation of the solution of gdlls by acids \va3 

 noticed bv M. Dizs'- See Annales ck Chimic, tome xxxv. p. 37. 



the 



