Materials and Formulas. 119 



made by dissolving 2 ounces in 10 gallons of water. After 

 six days the crop looked blighted, but the plants eventually 

 recovered. Most plants are seriously injured when not more 

 than one-fourth the above amount is used, and the solution for 

 this reason requires dilution to such an extent that its value as 

 an insecticide is largely destroyed. 



Arsenious acid may also be the cause of the death of a plant 

 if applied in solution at the roots. Jager 1 cites many cases in 

 which different plants were seriously injured or killed in this 

 manner, the action of the poison being to cause the entire plant 

 to wilt and finally to die. In one experiment, some young oat 

 plants were watered with a solution containing 1 part of arsenic 

 in 480 of water. The application was repeated a week later, 

 and two weeks from the beginning of the work most of the 

 plants were wilted to the ground, but some still remained fresh 

 and continued to grow. 2 Cuttings also absorb arsenic with the 

 same result as when the poison enters through the roots, for a 

 chemical examination showed arsenic to be present in the 

 tissues. 



In view of the above, arsenious acid or white arsenic cannot 

 be recommended as an insecticide. When combined with other 

 substances, however, it can be used with safety. Kilgore pub- 

 lished the following formula for combining arsenic and lime : 8 

 " A very cheap insecticide, having the same insecticidal proper- 

 ties as London purple, can be easily made by boiling together 

 for one-half hour in 2 to 5 gallons of water 



White arsenic (commercial) 1 pound, 



Lime [unslaked] 2 pounds, 



and dilute to required volume, say 100 gallons. ... It is desir- 

 able that the lime should be present in the boiling solution of 

 white arsenic since it renders the latter insoluble as fast as it 

 goes into solution, thus reducing the volume of water, and 

 shortening the time for obtaining the arsenite. When the 

 white arsenic is dissolved alone, a larger volume of water and 

 more time are required. When lime is added the precipitation 



1 Dr. Georg v. Jager, " Ueber die Wirkungen des Arseniks auf Pflanzen." Stutt- 

 gart, 1864. 

 a Ibid. 8, 9. 

 N. C. Agric. Exp. Sla. 1891, July, Bull. 77 b, 7. 



