152 RESEARCHES UPON ATOMIC WEIGHTS. 



It is to be noted that Series I and Series II yield percentages of silver 

 dififering by less than 0.004 per cent, a highly satisfactory agreement, which 

 indicates purity of the halogen acids employed as well as experimental 

 accuracy. 



If the percentage of silver in silver chromate is 65.0333, the molecular weight 

 of silver chromate may be calculated from the atomic weight of silver, and from 

 the latter value the atomic weight of chromium by difference. These calcula- 

 tions are carried out with two 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. 



If Ag = 107.880 Ag2Cr04 = 331.768 and Cr = 52.008 

 If Ag = 107.870 Ag2Cr04 = 331-737 and Cr = 51.997 



Although slightly lower than the previous investigations, these results agree 

 with them as closely as is to be expected, most of the probable 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 can not be completely dried without de- 

 composition. 



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 two assumed values for the atomic weight of silver referred to 

 oxygen, the atomic weight of chromiimi is found to have the following 

 values: 



If Ag = 107.88 Cr = 52.01 



If Ag = 107.87 Cr = 52.00 



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



