33° CONNECTICUT EXPERIMENT STATION REPORT, I907-I908. 



varied from 1.87 to 2.29; the high ratio shown in sample 18569 

 givfes addititttial evidence of the presence of considerable qtianti- 

 ties of white arsenic. The amount of arsenious oxide in combina- 

 tion With copper varied ff-om 49.63 to 55.88 per cent., with one 

 exception above thfe usual legal requii-emeht of 50 per cent. In 

 three of the samples the ambuht of arsenious oxide is more than 

 2.20 times that of the cOpper oxide, and the natural inference is 

 that eitlier arsenic has been added purposdy or that the material 

 has been carelessly manufactured. 



A comparison of the Water-soluble arsenic in Paris green and 

 lead acetate emphasizes one of the chief advantages gained by 

 using the latter itisecticide. In lead arsenate from 0^2 to 1.31 

 per cent, was soluble in ten days^ while in Paris green the solu- 

 bility ranged ir6hi 2.44 to io.72 per cent. 



DIRECTIONS FOR THE USE OF LEAD ARSENATE 

 AND PARIS GREEN AS INSECTICIDES. 



Lead arsenate as an insecticide was first used in the work of 

 the Gypsy Moth Commission in Massachusetts in the early nine- 

 ties and it has since been employed in controlling nearly all of the 

 leaf-eating insects, and has proved to be a valuable addition to 

 our list of available arsenical pcrisons. When devoured by 

 insects it is somewhat slower in its action than Paris green, and 

 should therefore be applied earlier, before much damage has been 

 done to the plants. On account of the excellent adhesive qualities 

 of lead arsenate, it remains upon the foliage for a long time, 

 while. Paris green soon washes off if rains are frequent. Lead 

 arsenate is gradually replacing Paris green as an arsenical insecti- 

 cide, and especially during the past season the high price of the 

 latter has induced many farmers and fruit growers to use lead 

 arsenate. Paris green has been used to destroy leaf-eating 

 insects ever since the Colorado potato beetle reached the Atlantic 

 States. It is therefore the old standard remedy, and in many 

 places is the only arsenical insecticide that can be purchased at 

 the stores. 



FORMULA FOR LEAD ARSENATE. 



As lead arsenate is sold in paste fotm, and even when cal- 

 culated as water-free contains less arsenic than Paris green, it is 

 necessary to use a larger quantity by weight of the commercial 



