212 



Successive in- 

 fusions in cold 

 water. 



Effects of re- 

 agents. 



Gallic acid 

 more leacliiy 

 soluble than 

 itan. 



CN VEGETABLE ASTRINGENTS. 



and following infusions, up to the 71b inclusive, were als» 

 more or less covered with mould, and had deposited a sedi- 

 ment, but the fluid was now iu nil of them transparent, and 

 of different shades of brown. The remaining infusions, after 

 the 7th, had undergone no change, their colour was very 

 b.right^aad in the two last, scarcely perceptible. A com- 

 parative experiment was made at the same time with ano- 

 ther portion of galls, which was subjected to the same ope- 

 ration, except that it was not boiled, but only suffered to 

 remain for twenty-four hours at the common temperature of 

 the atmosphere. The cold infusions were generally of a 

 deeper brown colour, they continued to act upon the re- 

 agents longer than the warm infusions, so that it was not till 

 after the 14th, that the effect of the iron ceased to be visi- 

 ble. Generally the cold infusions begin to mould sooner 

 than the warm ones, but I thought that they deposited less of. 

 the sediment. The effects of the three reagents, jelly, the 

 oximuriate of tin, and the oxisulphate of iron, upon the in- 

 fusions were noticed in every instance when they were fisft 

 formed; in the earlier infusions the precipitates were very 

 copious, but their quantity gradually diminished, until first, 

 they were no longer produced by the oximuriate of tin, and,, 

 shortly after by jelly, but it required a considerable number 

 of additional infusions to exhaust the whole of the gallic 

 acid. If the infusions be formed as in the above experi- 

 ment, it generally happens, that after the 7th or 8th period 

 the oximuriate of tin ceases to produce a precipitate, jelly 

 continues to be perceptible for one or at most two infusions 

 more, while the iron produced the black stain until the 12th, 

 13th, or 14th infusion. 



When the three reagents mentioned above are added to 

 the infusion of galls at different lengths of time after its for- 

 mation, the iron is the first which produces an effect ; while 

 the jelly and the oximuriate of tin commence later, and 

 nearly about the same period. The gallic acid is so readily 

 soluble in water, aud it is detected with so much minuteness 

 by the oxisulphate of iron, that almost at the same instant 

 that the galls are added to the water, does the fluid become 

 capable of producing the gallate of iron. I have uniformly 

 found the effects of these reagents to follow this order, al- 

 though 



