CERIUM. 335 



CERIUM. 



Although cerium was discovered almost at the beginning of the present 

 century, its atomic weight was not properly determined until after the 

 discovery of lanthanum and didymium by Mosander. In 1842 the in- 

 vestigation was undertaken by Beringer,* who employed several methods. 

 His cerium salts, however, were all rose-colored, and therefore were not 

 wholl}'- free from did\nnium ; and his results are further affected by a 

 negligence on his part to fully describe his analytical j^rocesses. 



First, a neutral solution of cerium chloride was prepai'ed by dissolving 

 tlie carbonate in hydrochloric acid. This gave weights of eerie oxide and 

 silver chloride as follows. The third column shows the amount of CeO.^ 

 proportional to 100 parts of AgCl : 



CeO.,. AzCL Ratio. 



Mean, 40.469, ± .0415 



The analysis of the dry cerium sulphate gave results as follows. In 

 a fourth column I show the amount of CeOj proportional to lOO parts of 

 Ba80, : 



.042 



Beringer also gives a single analysis of the formate and the results of 

 one conversion of the sulphide into oxide. The figures are, however, 

 not valuable enough to cite. 



The foregoing data involve one variation from Beringer's paper. 

 Where I put CeO.^ as found he puts CcjO,. The latter is plainly inad- 

 missible, although the atomic weights calculated from it agree curiously 

 well with some other determinations. Obviously, the presence of didym- 

 ium in the salts analyzed tends to raise the apparent atomic weight of 

 cerium. 



Sliortly after Beringer, Hermann f published the results of one experi- 

 ment. 23.-532 grm. of anhydrous cerium sulphate gave 29.160 grm. of 

 BaSO^. Hence 100 parts of the sulphate correspond to 123.926 of BaSO^. 



*Ann. Cherti. Pharm.,42, 134. 1S42. 

 t Journ. fiir Prakt. Chem., 30, 1S5. 1843. 



