88 



RESEARCHES UPON ATOMIC WEIGHTS. 



When the results of Series I and II are averaged with those of Series III, it 

 is found that 



If Ag = 107.880 As = 74.957 



If Ag = 107.870 As = 74.944 



The atomic weight of arsenic is being subjected to further investigation in 

 this laboratory, by determination of the ratio of arsenic trioxide to iodine. 



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 trisodium 

 arsenate probably contains occluded basic impurity. 



3. It is shown that silver arsenate can not be completely dried without 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 two assumed values for the atomic weight of silver referred to 

 oxygen 16.000, the atomic weight of arsenic is found to have the following values : 



If Ag = 107.88 

 If Ag = 107.87 



As = 74.96 

 As = 74.94 



