294 Journal of Agricultural Research voi. xm, no. s 



ness in the season, the trials were limited. During the coming spraying 

 season more elaborate field experiments will be conducted by Prof. Lovett 

 and reported upon at a later date. 



SUMMARY 



(i) This paper reports a chemical study of the calcium arsenates. 



(2) Pure calcium hydrogen arsenate (CaHAs04) and tricalcium arse- 

 nate [Ca3(As04)2] have been prepared and methods for their preparation 

 outlined. 



(3) The specific gravity for calcium hydrogen arsenate was found to 

 be 3.48; that for tricalcium arsenate 3.31. 



(4) The solubitity of calcium hydrogen arsenate in 100 gm. of water 

 at 25° was 0.310 gm. and that of tricalcium arsenate was 0.013 g"^- 



(5) A chemical study of the relative stability showed that (a) there was 

 no apparent reaction between either calcium hydrogen arsenate or tri- 

 calcium arsenate and lime-sulphur when combined at a dilution used in 

 field spraying, (b) The addition of excess of calcium oxid to either of 

 the calcium arsenates prevented arsenic from going into solution, (c) 

 Some commercial substitutes for lime-sulphur reacted with both of the 

 calcium arsenates, (d) The arsenates reacted with or became soluble 

 in organic acids and various salts, such as sodium chlorid. 



(6) The composition of various commercial arsenates is given and 

 commented upon. 



