French National Instihite. 2Si 



mistry to the arts, which consisted in rendering common 

 jikims equal to Roman akmi for dyeing, and we have seen 

 that it is only requisite to purify them from a little iron. 



To the different methods invented for this purpose, M. Se- 

 quin, a correspondent, has added a new one, taken from 

 the difi'orence and the solubility of pure alum and aium 

 charged wiih iron. He dissolves sixteen parts of common 

 alum in 2 J- of water, allows it to crystallize, and hy this me- 

 thod obtains 11 parts of alum as pure as that of Rome, and 

 almost as pure as that of Liege. 



We may applv this process to the first manufacture, and 

 obtain at once an alum a third more in value. 



The same chemist has continued his labours upon the 

 analysis of the juices of vegetables. 



He has recently treated of those v/hich contain no tannin; 

 all have n^ore or less albumen and bitter principle. The 

 more abundant the albumen is, the stronger is the smell, 

 and the sap is more easily corrupted. Mushrooms, cruci- 

 ferae and solanice are of this description. M. vSeiuip gives 

 a view of the proportion of these two principles, in twenty- 

 two natural families of plants, by remarking in several the 

 differences of these proportions in the various parts of the 

 vegetable, and in the same plant taken at different ages. 

 All these saps, treated by the sulphuric acid, or the mu- 

 riate of tin, acquired the smell of pears or boiled apples, and 

 sometimes of fermented liquor, like cyder and beer. 



What renders this description of researches so diflicult, is 

 the prodigious quantity of reactions, and various combina- 

 tions, which enter into elementary substances so few in 

 themselves. 



Wc have had new proofs of this in the memoir of 

 M. Thenard, professor in the college of France upon nitric 

 ether. 



Wc know that the ethers are odoriferous and combusti- 

 ble liquors, which arc obtained by treating alcol'.ol with the 

 acids. The bost'known is the sulphuric ether. We are in- 

 debted to the inquiries of Messrs. Fourcroy and Vauijueliu 

 for being acquainted with the progress of its form.ation, and 



all 



