Insecticides and Delated Substances. 301 



Haywood gives the following directions for preparing lead 

 arsenate ; for each pound of lead arsenate to be made, use 



Ounces 



Formula A. Sodium arsenate (65 per cent) 8 



Lead acetate (sugar of lead) 22 



Formula H. Sodium arsenate (65 per cent) 8 



Lead nitrate 18 



Dissolve each salt separately in 1 to 2 gallons of water, using 

 wooden vessels. When dissolved, pour the lead solution into the 

 sodium arsenate, stirring thoroughly until the mixture just turns 

 a potassium-iodide test paper to a bright yellow. The lead salt 

 is then in slight excess. A large excess should be avoided. Al- 

 low the lead arsenate to settle, and pour off the liquid. These 

 chemicals are extremely poisonous and should be plainly labeled 

 and handled with care. 



Pink arsenoid is a commercial preparation made by adding 

 lead acetate to sodium arsenite and coloring the insoluble product 

 with a dye. It is composed chiefly of lead arsenite, only a small 

 proportion of the arsenic being soluble, and has given satisfac- 

 tory results. 



White arsenoid was the product of an attempt to put barium 

 arsenite upon the market as an insecticide. Contrary to expec- 

 tation, all the arsenious oxide of this preparation was found to 

 be soluble in cold water. It gave poor results and was short- 

 lived. 



White arsenic, or the simple arsenious oxide, has been used as 

 a constituent of "dips" and various insect and animal poisons. 

 It is volatile at a comparatively low heat and mixed with sulphur, 

 it has been successfully used against ants by forcing the vapors 

 into the nest. 



Arsenical poisoning may occur in the case of trees heavily 

 sprayed with arsenical insecticides. Headden found arsenic in 

 diseased fruit trees and this condition was correlated with an 

 accumulation of arsenic in the soil in compounds from which it 

 was rendered gradually soluble by the salts of the soil solution. 



