9 



In the next table are given data showing the effect upon the 

 flow of water through the soil. The apparatus used was very simi- 

 lar to that described above except that the soil column was kept 

 under a constant head of one inch of a solution containing 200 

 parts per million arsenic. The amount passing through was 

 measured at various intervals. 



EFFECT OF ARSENIC ON PERCOLATION OF WATER 

 THROUGH SOILS. 





Soil 



No. 1 



Soil 



No. 2 



Soil 



No. 3 



Time 



Blank 



Arsenic 



Blank 



Arsenic 



Blank 



Arsenic 





c.c. 



c.c. 



c.c. 



c.c. 



c.c. 



c.c. 



8 hrs 



286 



416 



78 



183 



134 



128 



24 " 



695 



650 



90 



94 



225 



164 



32 " 



365 



230 



35 



18 



119 



38 



48 " 



910 



680 



67 



18 



236 



37 



56 " 



400 



305 



28 









72 " 



770 



420 



40 



18 



37 



6 



80 " 



420 



135 











98 » 



620 



240 



44 



14 







112 " 



950 













Thus it may be seen that the deflocculating action of this 

 chemical is directly related to the movement of water. It causes 

 the soil particles to swell, more especially in the organic soils 

 and as the concentration increases a water logged condition en- 

 sues. It also accentuates the colloidal state thus increasing the 

 friction and thereby making the passage of water more difficult. 



Biological Influences. 



Arsenic belongs to the diss of chemicals known as very 

 strong poisons. All forms of plant and animal life are influenced 

 by these chemicals, the degree of effectiveness depending on the 

 amount of arsenic present and the degree of resistance exhibited 

 by the plant or animal. Among the most important lower plants 

 within the soil are the bacteria which ammonify and nitrify the 

 nitrogenous material, thus rendering the inert componds of this 

 element available to the plants. The rate of ammonification or 

 nitrification is even greatly influenced by the presence in the soil 

 of excessive amounts of salts generally considered comparatively 



