8 BULLETIN 480, U. S. DEPARTMENT OF AGRICULTURE. 



the proper amount of moisture, otherwise a larger amount of actual 

 arsenate of lead may be used than is necessary. 



Dry arsenate of lead has been tried on a small scale and has given 

 good results. It has not been used extensively, as it is more expen- 

 sive than the paste form. 



MIXING POISON. 



Arsenate of lead in paste form can be obtained in different- 

 size steel drums or wooden packages, and should contain 50 per cent 

 water. The lead, being heavier than the water, readily settles at the 

 bottom of the container and should be stirred to an even consistency 

 before being mixed with water for spraying. If this is not properly 

 done an uneven strength of the solution is the result and consequently 

 spraying operations are often unsatisfactory. This is one of the 

 parts of a spraying operation that is easiest to neglect, and in order 

 to secure an even solution a mixer has been devised, as shown in 

 Plate VIII. It can be attached to a 100-pound drum of arsenate of 

 lead and the contents brought to an even consistency in from 3 to 5 

 minutes. The lead should be poured into another drum to make sure 

 it is thoroughly mixed, thus increasing its efficiency and lessening 

 the cost of labor. 



AGITATION. 



Agitation is one of the most important factors in the operation of 

 any spraying machine, owing to the fact that if constant and 

 thorough agitation is not maintained uneven results may be expected. 

 In some power machines the agitator is in motion only when the 

 pump is working, but this is not a satisfactory arrangement. If the 

 machine is moved from one location to another and the pump is 

 stopped a large part of the poison will settle to the bottom of the 

 tank. It is very difficult to get arsenate of lead again into suspen- 

 sion, under such conditions, as it has to be sucked gradually from 

 the bottom of the tank by the agitator, which will not function as 

 well as if the poison is not allowed to settle. 



On all machines the agitator should be directly connected with the 

 engine and when the pump is not in use the engine should be run 

 slowly, so as to keep the solution well mixed until the tank is empty. 



AMOUNT OF SOLUTION TO BE USED. 



The amount of solution used in solid-stream spraying should be 

 carefully guarded, as it is very easy for considerable waste to occur. 

 With high-power outfits using 1-inch hose and one-fourth-inch tip 

 on the nozzle, from 25 to 35 gallons of solution is being delivered 



