392 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Second Series. UBr 4 : 4AgBr. 



Third Series. UBr 4 : 4Ag. 



No. of 

 Analysis. 



10(7) 

 11 (8) 

 12(9) 



Weight of 



Uranous 



Bromide 



with all 



Corrections. 



1.7999 

 1.0662 

 1.8551 



Weight of Sil- 

 ver in vacuo 

 (not corrected 

 for Sodic 

 Bromidf). 



grams. 



1.39365 

 0.82559 



1.43817 



Weight of 



Silver 



with all 



Corrections. 



grams. 

 1.3918 



0.8245 



1.4342 



Wt. of Uranous 

 Bromide corre- 

 sponding to 

 100 grams 

 Silver. 



grams. 

 129.322 



129.315 



129.347 



Atomic 

 Weight of 

 Uranium. 



238.49 

 238.46 

 338.60 



Average 238.52 



Average of all determinations . . 

 Average of six final determinations 



238.52 

 238.53 



the weighings were actually made to the hundreths of a milligram the 

 final corrected data are rounded off to the nearest tenth of a milligram, 

 since the deviations of the results show that the hundredths could have 

 had no significance. 



The extreme difference between the highest and the lowest values in 

 the preliminary series is 0.33 unit, in the second series 0.09 unit, and in 

 the third series 0.14 unit. At first sight these variations seem large, but 

 their relative magnitude appears smaller when the great molecular weight 

 of uranous bromide, 558.34, is taken into consideration. Thus the 

 extreme percentage error of the preliminary series is 0.06, while those 

 of the last two series are only 0.016 and 0.024 per cent respectively. 



