l80 MAINE AGRICULTURAL EXPERIMENT STATION. I9OO. 



dissolved separately in water and slowly poured together with 

 stirring. 



Arsenate of lead is made by William H. Swift & Company, 

 Boston, Mass., and the Bowker Chemical Company also of Bos- 

 ton. The latter company sell the goods under the name of Dis- 

 parene. The chemist of one of the companies was for several 

 years with the Gypsy Moth Commission and while with them 

 constantly urged farmers to make arsenate of lead by the above 

 formula and use it as an insecticide. Because of this we asked 

 him why he now recommends the consumer to buy the "ready 

 made" instead of using "home made"' arsenate of lead. His 

 reply (in part) is as follows : 



"Between the years 1896 and 1899 Prof. C. H. Fernald and I, 

 as opportunity offered, preached faithfully the gospel of home 

 made arsenate of lead to our fruit growers and farmers. We 

 had to do this. There was no one making it. As a result of 

 these continued efforts not more than 15 or 20 farmers tried it. 

 Most of them found it too expensive ; many of them injured their 

 foliage because of poor chemicals, wrong formula or improper 

 mixing. 



"The objections to the use of the home made article are the 

 difficulties attending its manufacture. The more important are : 



"To obtain arsenate of soda free from adulteration. In our 

 experience in the gypsy moth work we were greatly bothered 

 with adulterated arsenate of soda. Made as it generally is, by 

 the use of rock salt, there is more or less of the latter left in the 

 arsenate of soda. When mixed with a solution of lead salts, the 

 sodium chloride acts first, forming lead chloride, which has no 

 value as an insecticide ; later, the arsenate of soda reacts, but 

 often there is not lead enough allowed for the complete neutral- 

 izing of the latter.- This leaves soluble arsenic in the mixture 

 and "burned" foliage results. We went over the ground fully 

 in our gypsy moth work and finally had to import arsenate of 

 soda from England in order to get a pure article. 



"The. establishing a correct formula. Commercial arsenates 

 of soda vary from 50 per cent to 98 per cent in purity.* The 

 ordinary formula, 11 ounces sugar of lead to 4 ounces arsenate 

 of soda applies to the 50 per cent article. For the 65 per cent, 

 less arsenate of lead must be taken ; for the 98 per cent, still less. 



