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 follows : 



.7870 grm. oxide gave 1.2765 grm. sulphate. 61.653 P er cent, oxide. 



Hence Er = 167.82. 



Hoeglund, f following the method of Bahr and Bunsen, gives these 



results : 



Er. 2 O,. Er^(SO^. A . Per cent. Er. 2 O 3 . 



1 .8760 grm. 3.0360 grm. 61.792 



1.7990 " 2.9100 " 61.821 



2.8410 " 4-5935 " 61.848 



1.2850 " 2.0775 " 61.853 



1.1300 " 1.827 " 61.850 



.8475 " r -37Q " 61.861 



' Mean, 61.8375, .0063 

 Hence Er = 169.33. 



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

 studied by Hoeglund \vas largely ytterbia. 

 Humpidge and Burney give data as follows : 



1.9596 grm. Er 2 (SO 4 ) 3 gave 1.2147 g rm - Er. 2 O 3 . 61.987 per cent. 

 1.9011 " 1.1781 " 61.965 " 



Mean, 61.976, -0074 



Hence Er= 170.46. 



The foregoing data were all published before the composite nature of 

 the supposed erbia was fully recognized. It will be seen, however, that 

 three sets of results were fairly comparable, while Delafontaine evidently 

 studied an earth widely different from that investigated by 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 : 



Er. 2 O 3 . Er.i(SO^ y Per cent. Er. 2 O 3 . 

 1.0692 1.7436 61.321 



1.2153 1.9820 61.317 



.7850 1.2808 61.290 



Mean, 61.309, d= .0068 



Hence, with S0 3 = 79.465, Er == 165.059. 

 If =16, Er= 166.316. 



*Ann. Chem. Pharm., 137, 21. 1866. 



fK. SvenskaVet. Akad. Handlingar, Bd. i, No. 6. 



I Wiedemann's Beibliitter, 5, 122. 1881. 



# Journ. Chem. Soc., Feb., 1879, p. 116. 



|| K. Svensk. Vet. Akad. Handlingar, No. 7, 1880. Abstract in Compt. Rend., 91, 382. 



