ERBIUM, YTTERBIUM, ETC. 361 



Bahr and Bunsen * give a series of results, representing successive puri- 

 fications of the earth which was studied. The final result, obtained by 

 the conversion of oxide into sulphate, was as follow\s : 



.7870 grm. oxide gave 1. 2765 grm. sul[ihate. 61.653 P*^' cent, oxide. 



Hence Er = 169.33. 



According to Thalen,t spectroscopic evidence shows that the " erbia 

 studied by Hoeglund was largely ytterl)ia. 



Humpidge and Burney§ give data as follows: 



1.9596 grm. Er2(SO^)3 gave 1.2147 grm. Er.^O^. 61.987 per cent. 

 I. 9011 " 1.1781 " 61.965 " 



« Mean, 61.976, =b .0074 



Hence Er= 170.46. 



The foregoing data were all published before the con:posite nature of 

 the su[)posed erbia was fulh^ recognized. It will be seen, however, that 

 three sets of results were fairly comparable, while Delafontaine evidently 

 studied an earth widely difi'erent from that investigated b_v the others. 

 Since the discovery of ytterbium, some light has been thrown on the 

 matter. The old erbia is a mixture of several earths, to one of which, a 

 rose-colored body, the name erbia is now restricted. For the atomic 

 weight of the true erbium Cleve || gives three determinations, based on 

 syntheses of the sulphate after the usual method. His weights were as 

 follows, with the percentage ratio added : 



*Ann. Chem. Pharm., 137, 21. 1S66. 



tK. Svenska Vet. Akad. Handlingar, Bd. i, No. 6. 



j Wiedemann'.s Beiblatter, 5, 122. iSSi. 



j! Journ. Cheni. Soc, Feb., iSyg, p. 116. 



II K. Svensk. Vet. Akad. Handlingar, No. 7, iSSo. Abstract in Compt. Rend., 91, 3S2. 



