UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 750 , 



Joint Contribution from the Bureau of Chemistry 

 CARL L. ALSBERG, Chief 



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and the Insecticide and Fungicide Board 

 J. K. HAYWOOD, Chairman 



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Washington, D. C. 



Professional Paper 



October 5, 1918. 



A METHOD FOR PREPARING A COMMERCIAL 

 GRADE OF CALCIUM ARSENATE. 



By J. K. Haywood, Chief, Miscellaneous Division, and Chairman, Insecticide 

 and Fungicide Board, and C. M. Smith, Assistant Chemist. 



CONTENTS 



Page. 



Calcium arsenate as a substitute for 



lead arsenate. 1 



Preparation of calcium arsenate 2 



Slaking the lime 4" 



Proper proportion of arsenic oxirl and 



lime 4 



Page. 



Effect of dilution and temperature up- 

 on the compound 7 



Experiments with limestone 9 



Summary '. 9 



Labeling the product 10 



CALCIUM ARSENATE AS A SUBSTITUTE FOR LEAD ARSENATE. 



Recently attention lias been directed to the use of calcium arsen- 

 ate as a substitute for lead arsenate, principally because of the 

 cheapness of lime as compared with lead oxid. While no one recom- 

 mends the use of calcium arsenate alone on tender foliage, experi- 

 ments by the United States Department of Agriculture 1 , the Cana- 

 dian Department of Agriculture 2 , and others have shown that it 

 gives excellent results on some of the more resistant plants, as well 

 as very promising results when combined with other sprays, es- 

 pecially sulphids, which cause to a greater or less extent the break- 

 ing up of lead arsenate. 



3 TJ. S. Dept. Agr. Bui. 278, Farmers' Bui. 908. 

 2 Crop Protection Leaflet 10. 



