Rates of Application of Sodium Arsenite 



Sodium arsenite is sold in both liquid and powder form. The 

 liquid form is preferable, because it is readily diluted. The 

 greyish sodium arsenite powder is more difficult to handle, because 

 it is not readily dissolved. In cold water, the powder dissolves 

 very slowly at rates over 1/10 pound per gallon. 



The heavy, syrupy, strongly-caustic sodium arsenite solution 

 now generally used weighs about 12.63 pounds per gallon and con- 

 tains 4 pounds arsenious trioxide (AS2O3) equivalent per gallon, 

 although 9 -pound material is coming into more general use. Parts 

 per million of this solution are calculated in relation of gallons 

 of weed killer to cubic feet of water. One gallon of 4-pound weed 

 killer to 4,000,000 pounds of water equals 1 part AS2O3 , by weight, 

 to 1,000,000 parts of water. Four million divided by 62.42 (weight 

 of 1 cubic foot of water) equals 64,082 cubic feet. Therefore, when 

 one gallon of weed killer is added to 64,082 cubic feet of water, 

 the mixture contains one part AS2O3 per million parts of water. 



The quantity of chemical required for a treatment may be 

 calculated as follows: Since one gallon in 64,080 cubic feet 

 equals one part per million, a 4 part per million treatment (the 

 usual recommended rate) requires 64,080 -^ 4 = one gallon per 

 16,020 cubic feet of water. Tables 5 and 6 give gallons of sodium 

 arsenite to use when area in acres and average depth in feet are known. 



Table 5. --Sodium arsenite application, using four-pound material 



Parts per million Gallons four-pound sodium arsenite solution 



(p .p .m.) per acre required 



Average depth of water in feet 



2.5 



4 

 5 



8 

 10 



Table 6. --Sodium arsenite application, using nine-pound material 



Parts per million Gallons nine-pound sodium arsenite solution 

 (p .p .m.) per acre required 



Average depth of water in feet 



7 



2.5 .75 1.5 2.25 3.0 3.75 4.5 5.25 6.0 



4 1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 



5 1.5 3.0 4.5 6.0 7.5 9.0 10.5 12.0 

 8 2.4 4.8 7.2 9.6 12.0 14.4 16.8 19.2 



10 3.0 6.0 9.0 12,0 15.0 18.0 21.0 24.0 



25 



