52 ATOMIC WEIGHT DETERMINATIONS. 



oxalate, the precipitate incinerated and the oxide weighed. 

 The result was Di = 594.46, on the prot-oxide hypothesis, 

 fQY g _ 200. In one experiment the chloride was decom- 

 posed with argentic nitrate, oxychloride being filtered off 

 and allowed for, and the argentic chloride weighed, ihis 

 experiment gave Di = 592.54 for CI = 443.2. For the prep- 

 aration of the salt see Lanthaninm. {Erdmami s Journ.fur 

 Prak. Chem., 83, 1861, 387.) 



H. ZscniESCHE : About lU (0 = 16). 



In five experiments the sulphate was exposed to a white 

 heat until the weight became constant and the oxide on 

 beino- tested showed no traces of sulphur. The results 

 varied from Di = 46.585 to 48.08, probably, Zschiesche 

 thinks, on account of the presence of La. S ^16. Di was 

 separated from La by the partial precipitation of the nitrates 

 with oxalic acid, the first portion falling being redissolved, 

 and the partial precipitation repeated twenty times. [J^rd- 

 mann's Journ.fur Prak. Chem., 107, 1869, 74. 



C. Erk : IJ^.695 (O = 16). 



The sulphate was decomposed with ammonium oxalate, 

 the oxalate incinerated and the oxide weighed. The sul- 

 phuric acid was also precipitated as barium salt, and 

 weighed. Three experiments gave a mean of Di == 95.13, 

 on the prot-oxide hypothesis, with an extreme difference of 

 0.78. The Di salt was found to contain yttrium which was 

 removed by repeated fractional precipitation with sodium 

 sulphate. This re-agent precipitates a double salt of Di and 

 sodium. The purification was continued until the atomic 

 weight became constant. {Kopp' s Jahresbericht, 1870, 819, 

 Jena' sc he Zeitschr,fUr Med. und Nat, 6, 299.) 



Casselmann thinks that the salt may still have retained 

 yttrium, and Fresenius objects to the barium sulphate 

 determination on the well-known grounds. {Fresenius' 

 Zeitschr, 10, 510.) 



D. Mendelejeff : 138 (O = 16). 



From the analogy between Di and cerium and other 

 elements, and from the fact that it forms two oxides, Men- 

 delejeff believes that its lower oxide is a sesqui-oxide, and 

 its atomic weight 138. Mendelejeff points out that an 

 error is to be apprehended in the received values from the 

 fact that we have no guarantee of the pureness of Di salts 

 except recrystallization. {Liebig's Annal. Suppl. 8, 1871, 

 190.) 



