352 THE ATOMIC WEIGHTS. 



Another determination, with material refractionated from that used in 

 his investigation of the previous year, gave 58.512 per cent. Di. 2 3 and 

 Di = 145.40. 



These determinations, although concordant among themselves, are 

 still about a unit lower than those published in 1882, indicating that in 

 the earlier research some earth of higher molecular weight was present. 

 Accordingly, another series of fractionations was carried out, and the 

 several fractions of " didyrnia " obtained gave the following values : 

 Fraction. Per cent. Di^O^. At.Wt.^Di." 



i 58.355 H4.32 



2 58.479 i45- 16 



3 5 8 -5o 145-39 



4 58.755 i47.io 



c J 59.071 149.35 



' ' 1 59-086 149.46 



The last fraction is evidently near samaria (Sm = 150), and this earth 

 was proved to be present by a study of the absorption spectra of the 

 material investigated. 



Similar results, but in some respects more explicit, were obtained by 

 Cleve,* who also found that his earlier research had been vitiated by the 

 presence of samaria. He gives two series of syntheses of sulphate from 

 oxide, with two different lots of material, after eliminating samaria, and 

 obtains, computing with S0 3 = 80, values for Di as follows : ' 



First Series. 



Per cent. Di 2 O 3 . At. Wt. Di. 



58.088 142.31 



58.113 142.49 



58.047 142-03 



58.099 142.39 



58.104 142.42 



58.098 142.38 



58.104 142.42 



58.103 142.42 



58.070 142.19 



58.079 142.25 



Second Series. 



Percent. >/ 2 6> 3 . At. Wt. Di. 



58.125 142.57 



58-093 H2.35 



58.088 142.31 



58.111 142.47 



58.056 142.10 

 58.097 142.38 



58.057 142.10 



In short, the atomic weight of this " didymium " is not far from 142. 



*Bull. Soc. Chim., 39, 289. 1883. Ofv. K. Vet. Akad. Forhandl., No. 2, 1883. 



