BAXTER. — ATOMIC WEIGHT OF CHROMIUM. 417 



ference. Since the ratio of the atomic weights of silver and oxygen is 

 somewhat uncertain at the present time, these calculations are carried 

 out with various possible assumed values for the atomic weight of silver, 

 oxygen being assumed to have the value 16.000. It is to be noted that 

 the percentage error in the determination of the molecular weight of 

 silver chromate is multiplied six times in the atomic weight of chromium. 



IfAg= 107.93 Ag 2 Cr0 4 = 331.922 and Cr = 52.062 

 IfAg= 107.88 Ag a Cr0 4 = 331.768 and Cr = 52.008 

 If Ag= 107.85 Ag 2 Cr0 4 = 331.676 and Cr = 51.976 



Although slightly lower than the previous investigations, these re- 

 sults agree with them as closely as is to be expected, most of the prob- 

 able errors in earlier work tending to make the results too high. 



The more important results of this research may be briefly summed 

 up as follows : 



1. Pure silver chromate was prepared. 



2. It is shown that silver chromate cannot be completely dried with- 

 out decomposition. 



3. The proportion of residual water was determined in salt dried at 

 definite temperatures. 



4. The specific gravity of unfused silver chromate is found to be 

 5.625 at 25° C. referred to water at 4° C. 



5. The per cent of silver in silver chromate is found to be 65.0333 

 by two closely agreeing methods. 



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

 ferred to oxygen, the atomic weight of chromium is found to have the 

 following values : 



IfAg= 107.93 Cr = 52.06 



IfAg= 107.88 Cr= 52.01 



If Ag= 107.85 Cr = 51.98 



In the following paper the analysis of silver dichromate is described. 



We are greatly indebted to the Carnegie Institution of Washington 

 for generous pecuniary assistance in pursuing this investigation ; also 

 to the Cyrus M. Warren Fund for Research in Harvard University for_ 

 many pieces of platinum apparatus. 



Cambridge, Mass., 



December 10, 1908. 



vol. xliv. — 27 



