124 Chemistry and Chemical Arts. 
are found in rotten wood. Bodies analogous to these two acids are 
obtained when charcoal, soot, &c. are treated with nitric acid, and 
the product with an alkali. It is during this treatment with the al- 
kali, that they are formed. ‘They have a strong resemblance to the 
crenic acid; and Brerzexius supposed at first, that there was no 
difference between them, but he afterwards found one, actually to 
exist.— Ann. des Mines. 
2 Memoir on Tannin, Gallic, Pyrogallic, Ellagic and Meta- 
gallic Acids, by Peuovuze. (Ann. de Ch., t. 54, p. 337.)—Tan- 
nin is easily obtained in a state of purity, by the following process: 
The apparatus consists of a long and strait allonge resting upon a 
common decanter and terminating at its upper part by a glass ground 
stopper. A mesh of cotton is first introduced into the socket of the 
allonge, and upon it, the nut-gall reduced toa fine powder. The 
powder is slightly compressed, and when its volume is equal to half 
the capacity of the allonge, it is filled with the sulphuric ether of 
commerce. The apparatus is imperfectly corked, and left to itself. 
The next day the decanter will be found to contain two distinct 
strata of liquids ; the upper one very light and fluid, the lower one 
much more dense, of an amber color and a syrupy appearance. 
The nut-gall is not removed so long as the volume of the lower li- 
quid increases. When this has ceased, the two fluids are poured 
into a funnel, whose beak is stopped by the finger. After a few 
minutes repose, the lower stratum is run off into a capsule, and the 
upper one is put aside for distillation, in order to extract the ether, 
of which it chiefly consists. The heavy liquid is washed repeatedly 
in pure sulphuric ether, and afterwards placed in a stove or under 
the receiver of an air-pump. It disengages abundantly the vapor of 
ether and of water. The residue augments very sensibly in volume 
and leaves a spongy crystalline substance, very brilliant, sometimes 
colorless, but more frequently of a slightly yellow tinge. ‘This is 
pure tannin whose astringency is extreme and devoid of any other 
mixture of a bitter taste. By this process, one hundred parts of nut- 
galls, afford thirty to forty parts of tannin, which is always perfect- 
ly pure. 
The theory of the operation is as follows: of all the ingredients 
of the nut-gall, the tannin is the most soluble in water; conse- 
quently when aqueous ether is brought in contact with the finely 
powdered nut-galls, the water of the ether and a certain quantity 
of the ether, forms with the tannin a very dense syrup, which is 
