ATOMIC WEIGHTS 507 



Omitting the valueless experiments of Kjenilf/ we come next to the 

 figures published by Bunsen and Jegel " in 1858. From the air-dried 

 sulphate of cerium the metal was precipitated as oxalate, which, ignited, 

 gave CeOo. In the filtrate from the oxalate the sulphuric acid was esti- 

 mated as BaSO^ : 



1.5726 grm. sulphate gave .7899 grm. CeOj and 1.6185 grm. BaSO^. 

 1.6967 " .8504 " 1.7500 



Hence, for 100 parts BaSO^, the CeOs is as follows: 



48.804 

 48.575 



Mean, 48.689, ± .077 



Hence Ce = 138.48. 



One experiment was also made upon the oxalate: 



.3530 grm. oxalate gave .1913 CeOj and .0506 H„0 



Hence, in the dry salt, we have 63.261 per cent, of CeOo. 



In each sample of CeOo the excess of oxygen over Ce^O, was estimated 

 by an iodometric titration; but the data thus obtained need not be fur- 

 ther considered. 



In two papers by Eamiuelsberg ' data are given for the atomic weight 

 of cerium, as follows. In the earlier paper cerium sulphate was analyzed, 

 the cerium being thrown down by caustic potash, and the acid precipi- 

 tated from the filtrate as barium sulphate: 



.413 grm. Ce,( 804)3 gave .244 grm. CeO, and .513 grm. BaS04 



Hence 100BaSO4 = 47.563 CeOo, a value which may be combined with 

 others, thus; this figure being assigned a weight equal to one experi- 

 ment in Bunsen's series : 



Beringer 49.819, ± .042 



Bunsen and Jegel 48.689, ± .077 



Rammelsberg 47.563, ± .108 



General mean 49.360, ± .035 



It should be noted here that this mean is somewhat arbitrary, since 

 Bunsen's and Eammelsberg's cerium salts were undoubtedly freer from 

 didvmium than the material studied by Beringer. 



1 Ann. Chem. Pharm., 87, 12. 



a Ann. Chem. Pharm., 105, 45. 1858. 



spoggend. Aniialen, 55, 65; 108, 44. 



