LABORATORY MANUAL OF HORTICULTURE 



ARSENATE OF LEAD 



Arsenate of lead is another of our important insecticides and 

 to-day probably ranks first. It can be purchased in two forms 

 as a powder or as a paste. The paste form is the most widely 

 used. The usual formula for arsenate of lead is from two to 

 three pounds to fifty gallons of water, but the proportion varies 

 with the crop to be sprayed. 



Laboratory formula. Weigh out one-half ounce each of the 

 powdered and the paste form of arsenate of lead, and dissolve 

 each in a separate quart glass fruit jar of water. Study carefully 

 what takes place. Now place all three of the jars containing the 

 insecticides where the light will pass through them. Stir each 

 vigorously for a minute and note the results. Watch the solu- 

 tions for fifteen minutes, noting what takes place in each case. 

 Are the insecticides completely dissolved, forming a chemical 

 union, or are they held in suspension, with only a slight chemical 

 action taking place ? Discuss. Note accurately the length of 

 time required for each solution to settle. Discuss in detail why 

 it is absolutely necessary to have the spray mixture thoroughly 

 agitated during the whole time of spraying. 



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