INSECTICIDES 4T7 



tain the arsenic equivalent of at least 12| per cent arsenic 

 oxid (AS2O5). The wat(T soluble arsenic must not exceed an 

 equivalent of f of om^ per cent of arsenic oxid. Some of the 

 commercial preparations contain a larger j)ercentage of arsenic 

 than required by the law. In the best grades of arsenate of 

 lead paste the chemical is in a finely divided condition, and 

 thus when diluted for use remains in suspension for a con- 

 siderable time. If the paste contains less than 50 per cent 

 water it is likely to be lumpy and requires considerable time 

 and labor to get it into condition for use. 



Arsenate of lead is used at various strengths, depending upon 

 the insect to be killed and on the susceptibility of the foliage 

 to injury. Four pounds in 100 gallons can be used on the peach 

 if combined with the self-boiled lime-sulfur ; on apple four or 

 five pounds in 100 gallons is usually sufficient, although a greater 

 strength can be used without danger of injury to the foliage ; 

 on grapes for killing the grape root-worm beetles and the rose 

 chafer eight to ten pounds in 100 gallons have been found 

 necessary. The poison is more readily eaten by these beetles 

 if sweetened by two gallons of molasses in 100 gallons, but 

 unfortunately the addition of molasses greatly decreases the 

 adhesiveness of the poison. 



Arsenate of lead is also sold in the form of a powder. In case 

 the powder is fine enough to remain in suspension when mixed 

 with water it gives practically as good results as the paste form. 

 One pound of powdered arsenate of lead is equivalent to 2 

 pounds of the paste form. 



Homemade arsenate of lead. — Haywood and McDonnell 

 give the following directions for making arsenate of lead. 

 *' For every pound of arsenate of lead it is desired to make, use : 



J'ORMULA A : 



Ounces. 



Sodium arsenate (65 per cent) 8 



Lead acetate (sugar of lead) 22 



