BULLETIN No. 154 



PARIS GREEN. 



Chas. D. Woods and H. H. Hanson. 



Paris green is a definite chemical compound known to chemists 

 as aceto-arsenate of copper. It is prepared from verdigris 

 (acetate of copper) and arsenious oxide. When pure it carries 

 58.65 per cent arsenious oxide ; 31.29 per cent copper oxide; and 

 10.06 per cent acetic acid. The value of Paris green as an 

 insecticide depends upon the arsenic which it contains in com- 

 bination with copper. The presence of free arsenious acid is 

 harmful as it burns foliage. The ideal Paris green would carry 

 a maximum amount of arsenious oxide in combination with 

 copper; it would have as little as possible of free arsenious acid 

 so as not to burn the foliage ; and it would be in the finest pos- 

 sible powder in order that it may readily remain in suspension 

 when mixed in water and that it may be more thoroughly dis- 

 tributed over foliage. 



ANALYSES OF PARIS GREEN. 



During the past two years the Station has received frequent 

 complaints of the quality of Paris green, which has led to the 

 examination of the samples herewith reported. Analyses of the 

 Paris greens on sale in Connecticut in 1907 were reported by the 

 Connecticut Agricultural Experiment Station, and those on sale 

 in New Jersey by the New Jersey Agricultural Experiment 

 Station.* The results of the analyses made by these respective 

 Stations are here included with analyses made here. This exam- 

 ination of the fineness of many of these samples, which were 

 kindly frunished us by these Stations, were made at the Maine 

 Station and are reported on page 114. 



* Bui. 157 Conn. Station and Bui. 205 X. J. Station. 



