BAXTER AND JESSE. — ATOMIC WEIGHT OF CHROMIUM. 431 



The preceding table gives the results of all the final experiments in 

 the order in which they were carried out. The preliminary analyses, 

 which were defective in various ways, are not recorded. 



The results of the foregoing experiments are as concordant as one 

 can reasonably expect, since the insoluble silver salts are in general 

 difficult to obtain definite in composition. 12 The extreme values differ 

 by only one one hundredth of a per cent, while the averages of the dif- 

 ferent samples show an extreme difference of less than five thousandths 

 of a per cent. The composition of the dichromate is evidently not 

 affected by the concentration of the nitric acid frorn which it is 

 crystallized, since the averages from the different samples do not vary 

 regularly with the concentration of the nitric acid, the average result 

 obtained from Sample II being lower than that of either Sample I or 

 Sample III. 



If the per cent of silver in silver dichromate is 49.9692, the molecular 

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

 silver, and from the molecular weight of the chromate the atomic weight 

 of chromium by difference. Since the ratio of the atomic weights of 

 silver and oxygen is somewhat uncertain at the present time, these cal- 

 culations have been made 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 four times in the 

 atomic weight of chromium. 



If Ag = 107.930 Ag 2 Cr 7 7 = 431.986 and Cr = 52.063 

 If Ag = 107.880 Ag 2 Cr 2 7 = 431.786 and Cr = 52.013 

 If Ag = 107.850 Ag 2 Cr 2 7 = 431.666 and Cr = 51.983 



In the following table are given the results of the preceding research 

 upon silver chromate by Baxter, Mueller, and Hines, together with the 

 average of their values and those presented in this paper : 



Baxter, Mueller, and Hines. Average. 



If Ag= 107.930 Cr = 52.062 52.063 



If Ag= 107.880 Cr = 52.008 52.011 



IfAg= 107.850 Cr = 51.976 . 52.980 



The agreement of the two independently determined values is highly 

 satisfactory, no matter which value for the atomic weight of silver is 

 assumed, although the higher values for silver give slightly better 

 agreement. 



The atomic weights of both chromium and silver may be calculated 



12 Baxter and Coffin, These proceedings, 44, 184(1909); Baxter, Mueller, 

 and Hines, loc. cit. 



