362 



THE ATOMIC WEIGHTS. 



It is not wortli wliile to combine this result with the earlier determi- 

 nations, for they are now worthless. 



YTTERBIUM. 



For ytterbium we have one very good set of determinations by Nilson.* 

 The oxide was converted into the sulphate after the usual manner : 



Yb,0^. 



1.0063 gt"™. 

 1.0139 " 

 .S509 " 



•7371 " 

 1.0005 " 



1.0059 



Yb,{SO,\. 

 1. 6186 grm. 

 1.6314 

 1.3690 

 1.1861 

 1.6099 

 1.3022 

 1. 6189 



Per cent. Vb-j^O^. 

 62.171 

 62.149 

 62.155 

 62.145 

 62.147 

 62.126 

 62.134 



Mean, 62.147, d= .0036 



Hence, with SO3 = 79.465, Yb = 171.880. 

 If = 16, Yb = 173.190. 



TERBIUM, THULIUM, HOLMIUM, DYSPROSIUM, ETC. 



For these elements the data are both scanty and vague. Concerning 

 the atomic weights of holmium and dysprosium, practically nothing has 

 been determined. To thulium, Clevef assigns a value of Tm = 170.7, 

 approximately, but with no details as to weighings. Probably the value 

 was computed with SO3 = 80. 



For terbium, ignoring older determinations, Lecoq de Boisbaudran has 

 published two separate estimates.^ First, for two preparations, one with 

 a lighter and one with a darker earth, he gives Tb=: 161.4 and 163.1 

 respectively. In his second paper he gives Tb = 159.01 to 159.95. These 

 values probably are all referred to SO3 = 80. 



*Conipt. Rend., 91, 56. 1880. Berichte, 13, 1430. 



tCompt. Rend., 91, 329. 1880. 



X Compt. Rend., 102, 396, and iii, 474. 



