2tfS 



EXPERIMENTS ON HSTKINGENT VEGETABLES. 



Solutions of 

 neutral felts 

 preeip. Inf. 

 galls, but it is 

 not pure tanin. 



Metallic folu- 

 tions give denfe 

 preeip. 



probably con- 

 taining fomc of 

 the acid. 



Muriate of tin. 



Oxigenated ful- 

 phate of iron. 



became of a blue-green colour, and acted upon the falts of iron, 

 but not upon gelatine ; and there is every reafon to fuppofe, 

 that it held in folution a triple compound, of gallic acid, ful* 

 phuric acid, and lime. 



We owe to Mr. Prouft, the difcovery that different folutions 

 of the neutral falts precipitate the infufion of galls ; and he 

 fuppofes, that the precipitation is owing to their combining with 

 a portion of the water which held the vegetable matter in folu- 

 tion. In examining the folid matters thrown down from the 

 infufion, by fulphate of alumine, nitrate of potafh, acetite of 

 potafh, muriate of foda, and muriate of barytes, I found them 

 foluble, to a certain extent, in water, and poflefled of ihe 

 power of acting upon gelatine. From the produces given by 

 their incineration, and by their diftillation, I am however in- 

 clined to believe that they contain, befides tannin, a portion 

 of gallic acid and extractive matter, and a quantity of the fait 

 employed in the primitive folution. 



It is well known, that many of the metallic folutions occafion 

 denfe precipitates in the infufion of galls ; and it has been 

 generally fuppofed, that thefe precipitates are compofed of 

 tannin and extractive matter, or of thofe two fubflances and 

 gallic acid, united to the metallic oxide ; but, from the ob- 

 fervation of different proceffes of this kind, in which the falts 

 of iron and of tin were employed, I am inclined to believe, 

 that they contain alfo a portion of the acid of the faline com- 

 pound. 



When the muriate of tin was made to a6t upon a portion of 

 the infufion, till no more precipitation could be produced in 

 it, the .fluid that paflfed through the filtre ftill acted upon gelatine 

 and feemed to contain no excefs of acid ; for it gave a pre- 

 cipitate to carbonate of potafli, without producing effer- 

 vefcence. The folid compound, when decompofed by ful- 

 phuretted hydrogen, after the manner recommended by Mr. 

 Prouft, was found ftrongly to redden litmus-paper, and it 

 copioufly precipitated nitrate of filver : whereas, the primitive 

 infufion only rendered it flighlly turbid ; fo that there is every 

 reafon to believe, that the precipitate contained muriatic 

 acid, 



By paffing the black and turbid fluid, procured by the action 

 of folution of oxigenated fulphate of iron in excefs upon a 

 portion of the infufion, through finely-divided pure flint, con- 

 tained 



