PRINCIPLES OF SPRAYING 



clal form at a reasonable price. The prepara- 

 tion on the market is a finely pulverized precipi- 

 tate in two forms, one a powder and the other a 

 paste. These are probably about equally good 

 and are readily kept suspended in water. Less 

 free arsenic is contained in this form than in any 

 other compound of arsenic, making it safer to 

 use, especially in heavy applications. Arsenate 

 of lead may be used without danger of burning 

 the foliage as strong as five or six pounds to 

 fifty gallons of water, but three pounds is the 

 usual and a sufficient amount for the control of 

 any apple insect for which it is efficacious. 



Paris Green is being rapidly displaced by 

 arsenate of lead for several reasons. It is a 

 compound of white arsenic, copper oxide, and 

 acetic acid. The commercial form is a crystal 

 which in suspension settles rapidly, a serious 

 fault. It is more soluble than arsenate of lead 

 and hence there Is greater danger of burning 

 the foliage with it. Moreover, It costs from 

 twenty to twenty-five cents a pound, and the ar- 

 senate of lead can be purchased for from eight 

 to ten cents a pound. 



The amount which it Is safe to use In fifty 

 gallons of water is from one-half to three-quar- 

 ters of a pound. When paris green is used 

 III 



