228 UOAV CKOPS FEED. 



Carbon, 56.47 

 Hydrogen, 2.75 

 Oxygen, 40.78 



100.00 

 Crenate of copper is lastly [irecipitated as a grass-groe- 

 substance by adding acetate of copper to the liquid fron 

 which the apocrenate of copper was separated, and tlien 

 neutralizing the free acid with ammonia. From tliis com- 

 pound crenic acid may be prepared as a white, solid body 

 of sour taste, to which Mulder ascribes th(i formula C^^ 

 ■^24 ^16 "•" ^HjO, and in 100 parts the following compo- 

 sition • 



Carbon, 45.70 



Hydrogen, 4.80 



Oxygen, 49.50 



100.00 

 Mutual Conversion of Apocrcnic and frenic Acids, 



— When, on the one hand, apocrenic acid is placed in 

 contact with zinc and dilute sulphuric acid, the hydrogen 

 evolved from the latter converts the brown apocrenic acid 

 (by uniting with a portion of its oxygen) into colorless 

 crenic acid. On the other hand, the solution of crenic 

 acid exposed to the air shortly becomes brown by absorp- 

 tion of oxygen and formation of apocrenic acid. These 

 changes may be lepeated many times with the same por- 

 tion of these substances. 



Mulder remarks ( Chemie der Ackerkrume, p. 350) : 

 " In every fertile soil these acids always occur together in 

 not inconsiderable quantities. When the earth is turned 

 over by the plow, two essentially different processes fol- 

 low eacli other: oxidation, where the air has free access; 

 reduction, where its access is more or less limited by the 

 adhesion of the particles and especially by moisture. In 

 the loose, dry earth apocrenic acid is formed j in the firm, 



