EXPERIMENT STATION BULLETINS. 267 



ARSENIC AS A SUBSTITUTE FOR PARIS GREEN. 



For the fact that white arsenic is a dangerous thing to have around, 

 from its resemblance to such harmless household chemicals as salt, soda, 

 and baking powders, as well as the trouble required in preparing it for 

 use and the danger of burning the foliage if not properly prepared, we 

 have hesitated about recommending it for general use as an insecticide. 

 During the past two years the price of Paris green has more than doubled, 

 and owing to the ravages of the canker worm the necessity for the use of 

 arsenites has greatly increased, and as a matter of economy to farmers and , 

 fruitgrowers we give a method of preparing arsenic for use that will fur- 

 nish a remedy against chewing insects at less than one fourth the present 

 price of Paris green. As pure Paris green contains only about one half 

 the arsenic found in white arsenic, it will be seen that the latter will go 

 twice as far, and besides it is more likely to be free from adulteration. 



To Prepare Arsenic for Spraying. 



1 pound of arsenic. 



2 pounds of fresh lime. 

 400 gallons of water. 



Boil for twenty minutes in two gallons of water one pound of white 

 arsenic and two pounds of lime that has been carefully slaked. A light, 

 white precipitate will gradually form. White arsenic dissolves slowly even 

 in boiling water, but the lime unites with it as it dissolves and takes it 

 out of solution, so that a small amount of water will answer for the pur- 

 pose. The white precipitate formed is arsenite of lime, which is the same 

 as London purple without the coloring matter. This is nearly insoluble 

 and, as in the case of London purple and Paris green, the lime used with 

 it prevents injury to the foliage. If desired the water can be poured off 

 and the precipitate can be kept for future use. Before using the arsenic 

 dilute to four hundred gallons. As Paris green now sells for thirty cents 

 per pound at retail while white arsenic can be bought for ten or twelve 

 cents and will go twice as far, it can be seen that it will be much the 

 cheaper to use. 



There will be no danger of burning the foliage if the boiling be kept 

 up until all of the arsenic is dissolved and rendered insoluble by the 

 lime, but if this is not done it will be likely to do injury. Until one 

 has had experience in making the solution it will be well to test the 

 material upon a small scale before applying it to the orchard. 



The above method of making the arsenite of lime was given in Bulletin 

 77b of the North Carolina agricultural experiment station. 



Dr. Kedzie recommends the following method of preparing it: Boil in 

 one gallon of water one and one half ounces of white arsenic and five 

 ounces of sal-soda. This will quickly dissolve and the fact can be 

 observed, while in the other way it can not readily be determined. Add 

 two pounds of lime and dilute to forty gallons with water. 



This amount of lime furnishes a large excess, but will do no harm and 

 may be of advantage. 



If the arsenic in any form is to be kept, it will be well to color it with 

 soot, lamp-black, or some other material so that it may not be mistaken for 

 harmless chemicals. 



