492 



THE GYPSY MOTH. 



extract from his report on the result of these investigations 

 is given below : 



Paris green, a preparation of arsenite of copper, is insoluble in 

 water, but yields to it a small amount of arsenious oxide, with a 

 mere trace of copper. 



The Paris green employed in these examinations was a mixture 

 of several samples, all obtained from the Hampden Paint and 

 Chemical Company of Springfield, Mass. 



Its composition was as follows : 



Water, 



Copper oxide, 

 Arsenious oxide, . 

 Insoluble, .... 

 Other material and difference, 



Total, 



Per Cent. 



1.20 

 30.46 



59.94 



.12 



8.28 



100.00 



After allowing mixtures of Paris green and water to stand with 

 occasional agitation, I have found the following amounts of arse- 

 nious oxide in solution : 



The free arsenious acid would appear to be the cause of the 

 damage to the foliage. 



Alkaline substances generally neutralize arsenious acid, forming 

 with it salts known as arsenites. Lime, soda and potash are 

 materials which thus act. Any one of these could be added to 

 the mixture in such proportion as to exactly neutralize all free 

 acid. 



These substances, however, are sufficiently powerful as bases to 

 withdraw the arsenious acid from the copper. This is accom- 

 plished either partially or wholly, according to the favoring cir- 



