UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 750 
Joint Contribution from the Bureau of Chemistry 
CARL L. ALSBERG, Chief 
and the Insecticide and Fungicide Board 
J. K. HAYWOOD, Chairman 
JZ&* < &J°U 
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 oxid 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 has 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. 
U. S. Dept. Agr. Bui. 278, Farmers' Bui. 908. 
Crop Protection Leaflet 10. 
