Jig OU VEGETABLE ASTRINGENTS. 



added together, and a dense precipitate was formed, the fluid 

 was left transparent, and nearly in a ueutral state. The same 

 quantity of jelly as before was then added to f of the former 

 quantity of rhatany ; here a precipitate was thrown down, 

 which was less dense and of a lighter colour, the fluid was 

 lather less clear than in the former case, and it produced a 

 slight precipitate by the addition of more rhatany. A third 

 experiment was then performed the reverse of the last. The 

 original quantity of rhatany was added to -*- of its weight of 

 jell}' ; the fluid was rendered perfectly opake, but the pre- 

 cipitate very slowly subsided, and it continued for several 

 days to deposit fresh quantities of sediment, but no farther 

 precipitate was produced by the farther addition of jelly. 

 Beside this imperfect compound of tan and jelly, which I 

 suppose to be still retained in the fluid, it certainly contains 

 gallic acid, and probably the neutral and earthy salts, which 

 ;>re found in the gall-nut. I am not prepared to say, that 

 it is upon any of these substances that the oxide of tin acts ; 

 but I think, that we are justified in hesitating before we 

 conclude, that the precipitate which is formed depends upon 

 a substance, the existence of which is only rendered evident 

 by the process in question. 

 ?recipitaiioa The second proof, that has been brought of the exist- 

 the^annos^ ° ei,ce °* extract in the infusion of galls, is the circumstance 

 phere and heat f a part of the matter in solution being rendered insoluble 

 nroof oTthe ^y exposure- to the atmosphere, or by the application of 

 presence of heat, a property which is thought to he characteristic of 

 extract. ^^ p ecu ]] ar su bstance. Here again, without disputing the 



fact, I am inclined to hesitate as to the inference, and to 

 doubt, whether the matter which separates he confined to 

 this peculiar constituent of the fluid. If the infusion of 

 galls be evaporated by a heat not greater than that of boil- 

 ing water, a deep brown, brittle, transparent mass will be 

 obtained, which cannot be entirely redissolved ; and if the 

 clear part of the solution be poured off, and treated in the 

 same manner, an insoluble part will again be obtained; and 

 this operation may be repeated fa 1 - several times in succes- 

 sion on the same portion of fluid with the same result. I 

 have carried it to the fourth period, and I have observed no 

 dninge in the nature of the fluid, nor did its power of pro- 

 ducing 



