BAXTER AND COFFIN. — ANALYSIS OF SILVER ARSENATE. 197 



If Ag = 107.930 As = 75.021 



If Ag - 107.880 As = 74.957 



If Ag = 107.850 As = 74.918 



The atomic weight of arsenic will be further investigated in this 

 laboratory. 



The most important results of this research may be briefly summed 

 up as follows: 



1. Methods for the preparation of normal trisilver arsenate were 

 devised. 



2. It is shown that trisilver arsenate precipitated by means of tri- 

 sodium arsenate probably contains occluded basic impurity. 



3. It is shown that silver arsenate cannot be completely dried with- 

 out fusion. 



4. The specific gravity of unfused trisilver arsenate is found to be 

 6.66 at 25° C, referred to water at 4° C. 



5. The per cent of silver in silver arsenate is found to be 69.9616 by 

 three closely agreeing methods. . 



6. With several assumed values for the atomic weight of silver re- 

 ferred to oxygen 16.000, the atomic weight of arsenic is found to have 

 the following; values: 



'o 



If Ag = 107.93 As = 75.02 



If Ag = 107.88 As = 74.96 



If Ag = 107.85 As = 74.92 



A grant from the Carnegie Institution of Washington has been of 

 great assistance in the pursuit of this investigation. We are also in- 

 debted to the Cyrus M. Warren Fund for Research in Harvard 

 University for much indispensable platinum apparatus. 



Cambridge, Mass. 

 Nov. 24, 1908. 



