BULLETIN No. 210. 



DEPARTMENT OF ENTOMOLOGY. 



INJURY TO FOLIAGE BY ARSENICAL SPRAYS. 



XL CALCIUM ARSENATES AND ARSENITES. 

 III. NOTES ON OTHER ARSENICALS. 



BY H. T. FERNALD AND A. I. BOURNE. 



In Bulletin No. 207 of this station the effects of lead arsenate spraj^s 

 on foliage were discussed. In a similar way this bulletin gives the results 

 of studies with calcium arsenates and arsenites, and the factors which 

 appear to cause foliage injury following their use, together with notes 

 on other arsenicals. 



As in the case of the lead arsenates, the chemical work was done under 

 the supervision of Dr. E. B. Holland of the Department of Plant and 

 Animal Chemistry of the Experiment Station, and the applications of 

 the materials and studies of the results were made bj'' the Department 

 of Entomology. All the statements made in Bulletin No. 207 with refer- 

 ence to responsibility for the various parts of the work, methods of appli- 

 cation, and adequacy of methods, apply also to this part of the investi- 

 gation. 



II. CALCIUM ARSENATES AND ARSENITES. 



Materials. 



Pure Acid Calcium Arsenate. — To obtain pure calcium arsenate from 

 manufacturers proved impossible, and a quantity of this substance was 

 finally prepared by the Department of Plant and Animal Chemistry of 

 this station. It was the acid arsenate (CaHAs04.H20) and was a wliite 

 powder consisting of rhombic crystals varying in size and with about 1 

 per cent of them broken. Analyzed, it gave the following: — 



