SCIENTIFIC NEWS. 237 



Experiment 2. — I infufed, to a reduction of one half, an Nut-gall infufed 

 ounce of good gall nuts in fixteen ounces of water. The re- m wa ? er » 

 full was a brown infufion, which after many filtrations conti- 

 nued turbid. 



Experiment 3. — I mixed with the preceding infufion the The precipitate 

 precipitate of alumine, and frequently agitated the mixture with ° ad ^^ thThL 

 a glafs rod. The next day I filtered, and obferved that the fufion, combined 

 matter pafTed perfe&ly clear, which convinced me that the ^ptt."^" 

 alumine had precipitated the extractive. I wafhed the preci- 

 pitate with warm water, until the water no longer blackened 

 fulphate of iron, after which I left it to dry. 



Experiment 4.— As the alumine had evidently feparated the The clear fluid 

 extractive fubftance from the infufion of gall nuts, I could "!f; w ff SjlL. 

 only fuppofe that the liquor of the filtration mull contain tanin acid, 

 at the fame time with the gallic acid. I afcertained the pre- 

 fence of the latter, by a folution of fulphate of iron ; and to 

 difcover the former, I proceeded in the following manner. 



Experiment 5. — I diflblved two fcruples of ifinglafs in an But, bytheteft 



ounce of water, and poured a few drops of this folution into cLSeYno^ 



the liquor of the gallic acid ; they did not make it turbid in tanin. Confe- 



the leaft; which proved that it did not contain any tanin, ^ uent, y th 5 tanin 



' r i p , i -..was combined 



which, with the gelatine, ought to have formed an elaltic with the aiumine 



fubftance, infoluble in water. As the tanin was not difcover- of Ex P* 3« 

 able in this liquor, there remained no doubt of its having com- 

 bined with the alumine, which I afcertained in the following 

 manner. 



Experiment 6. — I digefted a portion of the precipitate of the Precipitate of* 

 infufion of gall nuts with diluted fulphuric acid. It was en- Jjjj^j^ajfc 

 tirely diflblved. The liquor pafled clear through the filter, acid, which 

 but coloured by the extra&ive*> natter. I dropped in a little { ^^ th f.* Iu " 

 of the ifinglafs folution, and immediately obferved white fila- tanin'was preci- 

 ments floating in the liquor, which by agitation formed into P' tated hy muci- 

 a mafs, pofleffing all the properties of tanned glue ; namely, 

 of becoming elaftic by heat, of foftening by water, infolubilitjr 

 in alcohol, &c. 



Experiment 7 . — The filtered liquor, as well as the water of The clear fol«. 

 the lixiviation in the third experiment, of courfe held in folu- ^ °^ " 

 tion nothing but the gallic acid. I concentrated the two fluids afforded fine 

 by flow evaporation, and obtained a fait in fine needles, which c 7 ftals of & ailic 

 was the pare gallic acid. 



Tfa 



