^^ Bxperm^is and Ohservatlom on the 



this process, it it contains extractive matter, that substanc« 

 is iji pa;t rendered insoluble, so as to tall to the bottom of 

 the vessel. When the fluid is reduced to a. thick consist- 

 ence, 1 pour alcohol upon it. It" any sallic acid or soluble 

 extractive mat. er be present, thev will oe dissolved, after a 

 little agitation, la the alcohol ; \vhil.-.l ihe mucilage, if any 

 exist, will remain unaltered, and may be separated from the 

 insoluble extract by lixiviation with water. 



I have made many experiments w ith the hope of disco- 

 vering a method by which the respective quantities of gallic 

 acid and extractive matter, when they exist in solution in 

 • the alcohol, may be ascertained, but without obtaining suc- 

 cess in the results. It is impossible to render the whole of 

 any quantity of extiactive matter insoluble by exposure to 

 heat and air, without at the same time decomposing a por- 

 tion of the gaHic acid. That acid cannot be sublimed with- 

 out being in part destroyed ; and, at the temperature of its 

 sublimation^ extractive matter is wholly converted into new 

 products. 



Ether dissolves gallic acid ; but it has comparatively little 

 action upon extractive matter. I have been able, in exa- 

 mining solutions of galls, to separate a portion of gallic 

 acid by means of ether. But when the extractive matter 

 is in large quantities, this method does not succeed, as, in 

 consequence of that affinity which is connected with mass*, 

 the greatest part of the acid continues to adhere to the ex- 

 tract. 



Alumine has a strong attraction for extractive matter, but 

 comparatively a weak one for gallic acidf. When car- 

 bonate of alumine is boiled for some time with a solution 

 containing extractive matter, the extractive matter is wholly 

 taken up by the earth, with which it forms an insoluble 

 compound ; but into this compound some of the gallic 

 acid appears likewise to enter ; and the portion remaining 

 dissolved in the solution is always combined with alumine. 

 I have not, in any instance, been able to separate gallic 

 acid and extractive matter perfectly from each other ; but I 

 have generally endeavoured to form some judgment con- 

 cerning their relative proportions, by means of the action 

 of the salts of alumine and the oxygenated salts of iron. 

 Muriate of alumine precipitates much of the extractive 



cftnt to the smell, in the water that comes over, cannot be detected by 

 chemical rtagints. 



■^^ See Beitholiet, R'cherches sur ks Lo,s de t Affin'Ue. Mem. de fln' 

 ititute National, ro Tie iii. p. r. 



t See Fie'Uer, Journal de Chimie, par J. B. VaiiMons, tome i. n. s?. 

 -* matter 



