10 



inert 5 . Thus their development and functions would be expected 

 to be greatly influenced by the presence of such a virulent poison 

 as arsenic. 



Ammonification. 



For determining the influence of arsenic toward the organ- 

 isms which bring about ammonification the following method was 

 used. One hundred grains of soil and 1 gram of dried blood were 

 weighed into glass tumblers, arsenite of soda added in varying 

 amounts, the moisture content brought up to the optimum point 

 and the whole well stirred. They were then incubated for 7 days 

 and the ammonia determined by the usual method. Results are 

 given in the following table : 



EFFECT OF ARSEXIC OX AXOIOXIFICATIOX. 





Soil No. 1 



Soil No. 2 



Soil No. 3 



Arsenic 



Ammonia in 



Ammonia in 



Ammonia in 



in soil 



100 gms. soil 



100 gms. soil 



100 gms. soil 



per cent. 



mgs. 



mg. 



mg. 



.001 



35.5 



98.4 



40.5 



.005 



21.3 



75.3 



43.0 



.010 



27.8 



83.3 



51.5 



.015 



35.1 



76.1 



48.0 



.050 



28.5 



71,4 



70.4 



.100 



33.0 



81.2 



90.0 



.250 



34.0 



76.0 



100.1 



.500 







85.8 



1.000 







99.1 



Check 



34.5 



87.1 



53.7 



From the above results it may be seen that in some propor- 

 tions a stimulation takes place while in others a retarding influence 

 is noted. Xo general law is applicable to all soils. The greatest 

 stimulation is noted in the organic soil (Xo. 3), being at .25 per 

 cent As 2 0 3 almost double that of the check. A strong stimulation 

 is also apparent even at the excessive content of one per cent. 

 The least stimulation is to be found in the soil of heaviest clay 

 content. Hence an obvious conclusion to be reached from these 

 results is that the influence of sodium arsenite on ammonification 

 depends primarily upon the mechanical composition of the soil 



