I9I3] 



/. E. Greaves 



TABLE 2 



Data pertaining to the ammonia produced in wo grams of soll containing dif- 

 ferent amounts, and different forms, of arsenic 



over one-third of the amount of ammonia formed in the total 

 absence of lead arsenate, showing that even this large quantity was 

 not sufficient to kill or even to entirely stop the activity of the soll 

 organisms. 



Paris green, on the other hand, acts as a strong poison to the 

 ammonifying organisms. Before the concentration of arsenic in 

 this form in the soil reached a concentration of 240 parts per mil- 

 lion, the ammonifying efficiency of the soil was reduced one-half. 

 Even 20 parts per million of arsenic retarded very materially the 

 ammonifying powers of the soil. At the highest concentration 

 tested (1,120 parts per million) practically no ammonia was formed. 



Arsenic trisulfide in the lowest concentration had a marked 



