HISTORY OF THE GALLIC ACID, $Q 



Mr. Bartholdi first points out a process for obtaining pure Oxiding sub- 

 gallic acid: he afterward treats this acid with metallic oxides : *J mce f I . brow . l » 

 B * the gallic acid 



and he says he has demonstrated, that all substances, which by slightly 



yield oxigen to the gallic acid, give it a brown colour; and c arrlD S«- 



that, in this process, it is the acid itself, which, being charred, 



forms by a slight combustion the colouring matter. 



To show this, he boiled red oxide of mercury for half an Boiled with 



hour in a solution of gallic acid, which assumed a blackish hue. oxlde of mer - 



° cury carbon 



In the residuum he found fluid mercury, mixed with a coally was produced, 



powder: he afterward saturated the lioour with carbonate of? 1 "*' 1 wonJd n $ 

 * l longer colour 



potash and soda, and the salts thus produced afforded no blue iron. 



precipitate with sulphat of iron. 



He obtained the same result with oxide of manganese. Oxide of man- 



Other experiments convinced IVJr. Bartholdi, that substances g a »ese the 

 by which oxigen js abstracted from gallic acid, renders its Diso^igenizirr- 

 colour lighter. I rendered, he says, a solution of gallic acid substa "« es . 

 as limpid as distilled water, by boiling it for some time with ac \^ 

 very pure and well powdered charcoal, of which I took double 

 the weight of the acid: it retained its limpidity as long as I 

 excluded the influence of the atmospheric air from it, and it 

 precipitated iron black. 



Mr. Bartholdi presumes, that we may thus effect the de- its astrin- 

 Struction ofits astringent property. ^ dtimctibk 



Qn this I shall not for the present make any observations . 

 as it is necessary to be acquainted with the following experi- 

 ments, to judge them explicitly. 



Extraction of the Gallic Acid. 



There are several processes for extracting the acid, from Modes of e*- 

 aralls. tractingthe 



^ gallic acid. 



Scheie's process. 



On one part of gall, nuts bruised and passed through a coarse Scheele's. 

 sieve, pour six parts of cojd water. Let them macerate in a 

 glass jar four days, shaking them, frequently : then filter, and 

 expose the liquor to the open air in the same jar, covered only 

 with blotting-paper. In a month's time the liquor will be 

 Covered with a thick pellicle of mould, without any precipitate 



being 



