RICHARDS. — ATOMIC WEIGHT OF BARIUM. 89 



From the Ratio of Baric Chloride to Silver. 



I. Five experiments, Stas's second method = 137.419 



II. Three experiments, first new method = 137.445 



III. Four experiments, second new method = 137.449 



IV. Two experiments, Stas's third method = 137.445 



137.440 



Before discussing these averages it may be well to recall the results 

 obtained from baric bromide. These last results may be divided into 

 two groups of two series each, the essential difference between the 

 two series depending upon their relative accuracy. 



From the Ratio of Baric Bromide to Argentic Bromide. 



I. Experiments 3 to 12 ; Ba = 137.424 

 II. Experiments 13 to 19 ; Ba = 137.439 



137.431 



From the Ratio of Baric Bromide to Silver. 



I. Experiments 3 to 12 ; Ba = 137.422 

 II. Experiments 13 to 19 ; Ba = 137.435 



137.428 

 Total average of four groups 137.434 



The four groups, including eleven series and forty-nine individual 

 results, are thus essentially unanimous in the verdict that the atomic 

 weight of barium is between 137.42 and 137.45. Upon closer ex- 

 amination of details, it is apparent that some of the series are more 

 trustworthy than others. In general, the first series of each group is 

 considerably less reliable than the following ones, for obvious reasons. 

 The first series of the fkst and second groups have the additional dis- 

 advantage of having been the victims of rather unsatisfactory methods. 

 Since the most probable errors tend in any case to lower the observed 

 atomic weight, the striking out of these lower results appears all the 

 more allowable. 



The more trustworthy results which remain may be averaged as 

 follows : — 



