EXERCISE XLIII 



THE STUDY OF PARIS GREEN AND ARSENATE OF LEAD 



Material. Paris green, powdered arsenate of lead, paste 

 arsenate of lead. 



Apparatus. Quart glass jars, stirring-rod. 



Insecticides differ from fungicides in that they are chemicals 

 used for the destruction of insects that prey upon cultivated 

 plants. There are two kinds of insecticides: namely, stomach 

 poisons, or insecticides that are eaten by the insects and kill by 

 being taken into the stomach ; and contact insecticides, or those 

 which are sprayed on the insects and kill by coming in contact 

 with their bodies. 



PARIS GKEEN 



Paris green, one of our important insecticides, is an aceto- 

 arsenite of copper, and Ehrmann has given the composition of 

 pure Paris green as follows : 



Copper oxide 31.29% 



Arsenious acid 58.65% 



Acetic acid 10.06% 



However, most samples show some variation from the above. 

 The free arsenic in the Paris green is dangerous to foliage, and 

 when Paris green is used alone, lime should be added to avoid 

 burning the leaves. 



The usual formula for spraying is 



Paris green 1 Ib. 



Water . '. , . . . . 100 to 300 gal. 



Laboratory formula. Weigh out one fourth of an ounce of 

 Paris green and place it in a quart fruit jar of water. Study 

 carefully the action of the poison when placed in the water. 

 Describe what takes place. Now with a stirring-rod vigorously 

 agitate the water. Does it mix with the water ? If not, why ? 

 Describe. Is Paris green in water a solution or a mixture ? 



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