White Arsenic. 77 



lie also gave directions for the manufacture of an insecticide, 

 in which white arsenic entered as one of the principal ingredi- 

 ents. It was made " by boiling together for one-half hour 

 in two to five gallons of water 



White arsenic 1 pound, 



Lime 2 pounds, 



and dilute to required volume, say one hundred gallons. ... It 

 is desirable that the lime should be present in the boiling solu- 

 tion of white arsenic, since it renders the latter insoluble as fast 

 as it goes into solution, thus reducing the volume of water and 

 shortening the time for obtaining the arsenite." 



Two other compounds of arsenic have been used for the de- 

 struction of insects, the first trial being made upon the Gipsy 

 moth, in Massachusetts. 1 One of these, the arsenate of soda, 

 " has been recommended by various parties as an insecticide," 

 but the results of the experiments show that it injures foliage 

 before an efficient quantity for the destruction of the cater- 

 pillars can be applied. The other, however, the arsenate of lead, 

 is promising. It was proposed as an insecticide in 1892, by 

 F. C. Moulton, a chemist in the employ of the Gipsy Moth 

 Commission. It was first tested against tent caterpillars in 

 1808, with the following results: 2 "The smaller proportions, 

 as | pound or less to 150 gallons of water, do not kill the cater- 

 pillars [Clisiocumpa Americana] as quickly as is desirable. . . . 

 The larger proportions seem unnecessary and would, of course, 

 be rather expensive for general field work, but some such pro- 

 portions as 1, 1^, or 2 pounds to 150 gallons of water would 

 prove entirely satisfactory so far as we can judge from these 

 experiments." When used as strong as 24 pounds in 150 gal- 

 lons of water, no injury to apple foliage resulted, which is 

 indeed remarkable when the small amount necessary to destroy 

 the insects is considered. 



Caustic and Non-poisonous Insecticides. 



Having thus traced the introduction of the various compounds 

 of arsenic, and their gradual adoption by agriculturists for the 

 destruction of chewing insects, there still remains the consider- 



i Fernald, Mass. Hatch Agric. Exp. Sta. 1894, April, Bull. 24. 2 Ibid. 5. 



