144 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 5 



The following tables deduced from the bulletin above referred to, 

 show the results of certain of the tests in a graphic way. 



TABLE NO. 1 

 Weight' and Percentage of Sediment in last 100 cc. 



TABLE NO. 2 

 Weight i and Percentage Settled out op 500 cc. above the last 100 cc. 



It is thus apparent that without soap added to the mixture arsenite 

 of zinc settles slightly quicker than arsenate of lead, but that with 

 the addition of soap the settling of both is retarded. This is particu- 

 larly striking with arsenite of zinc. In another test, not here reported, 

 more of this compound settled out in fifteen minutes without soap 

 than in fifteen hours with soap. 



Injury to the Bark of Apple 



Professor D. B. Swingle of the Biology Department of the Montana 

 Agricultural College is engaged in an extended study of the effects of 

 arsenical compounds upon vegetation, and in this connection has made 

 a series of tests on apple trees. During the season of 1910 the fol- 

 lowing compounds were used; arsenic acid, arsenic trioxide, arsenic 



• Dry weight of arsenate of lead used, 11.7 grams (20 grams paste). Dry weight arsenite of zinc used; 10.0 grams. 



