I30 



Journal of Agricultural Research vo1.xvi.no.4 



4, and 5. Not one of the compounds tested was toxic at the lowest con- 

 centration tested, 78 X lo'^ mole. All of the others became toxic at some 



fe: is b S?- J<) ^ ft J^ Hi ?5 55 



1^ tl^l^l^ tVll 



3 



^ ^ ^^^^^^^^ 



Fig. 3.— Graphs showing the molecular concentrations at which the various salts are toxic to 



nitrification 



of the concentrations tested. In 1 1 out of the 20 cases tested the point 

 of toxicity for the ammonifiers and nitrifiers were the same, whereas 



