358 THE ATOMIC WEIGHTS, 



From syntheses Yt = 88. 287 



From analyses " = 88.309 



These data of Jones were briefly criticised by Delafontaine,* who re- 

 gards a lower value as more probable. In a brief rejoinder f Jones 

 defended his own work; but neither the attack nor the reply needs 

 farther consideration here. They are referred to merely as part of the 

 record. 



For the percentage of yttria in the sulphate we now have eight series 

 of determinations, to be combined in the usual way : 



Popp 51.208, rb .01 10 



Delafontaine, first 49,998, rb .0810 



Delafontaine, second 48.230, .0550 



Bahr and Bunsen 49.2695, rb .0233 



Cleve, earlier 48.605, db .0096 



Cleve, later 48.503, .0029 



Jones, syntheses 48.467, rb .0025 



Jones, analyses 48.472, rb .0024 



General mean 48.532, rb .0015 



Hence, if = 15.879, .0003, and S = 31.828, .0015, 



Yt = 88.580, rb .0053. 



If = 16, Yt = 89.255. 



If only the four series by Cleve and by Jones are considered, the mean 

 percentage of yttria in the sulphate becomes 48.481. Hence Yt = 88.350, 

 or, with = 16, 89.023. 



This result is preferable to that derived from all the data, for it throws 

 out determinations which are certainly erroneous. Cleve's early series 

 might also be rejected, but its influence is insignificant. 



*Chem. News, 71, 243. 

 fChem. News, 71, 305. 



