No. 4„] 



THE ELM-LEAF BEETLE. 



297 



shows the necessary amounts of the ingredients where 

 acetate of lead is used : — 



Using nitrate of lead, the following amounts of ingredients 

 are necessary : — 



The use of fifty per cent arsenate of soda is not recom- 

 mended when the sixty-five per cent can be purchased at a 

 fair price, since the former product is generally adulterated 

 with common salt. Where large quantities of arsenate of 

 lead are to he prepared it will be advisable to buy as high 

 grade commercial arsenate of soda as possible, and to have a 

 chemist determine the amount of acetate or nitrate of lead 

 required for use with it. 



The quantity of arsenate of lead to be used as a standard 

 charge for the spraying tank having been decided upon, the 

 ingredients necessary to make this quantity are determined. 

 It will be desirable to make two ballasts, equal in weight 

 respectively to that of the arsenate of soda and the acetate 

 or nitrate of lead, in each case plus the weight of the scoop 

 on the balance scales used. These ballasts may be made of 



