CERIUM. 221 



Combining results, we have the following general mean : 



From gold series In = 1 13.417, zt: .074 



" oxide " " =113.385,^.060 



General mean " -^= 113.398, rh .047 



Or, if = 16, In = 113.659. 



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 investigation was 

 undertaken by Beringer,* who employed several methods. 

 His cerium salts, however, were all rose-colored, and there- 

 fore were not wholly free from didymium ; and his results 

 are further affected by a negligence on his part to fully 

 describe his analytical processes. 



First, a neutral solution of cerium chloride was prepared 

 by dissolving the carbonate in hydrochloric acid. This 

 gave weights of ceroso-ceric oxide and silver chloride as 

 follows. The third column shows the amount of CeOj pro- 

 portional to 100 parts of AgCl : 



CeO^. AsrCL Ratio. 



Mean, 40.469, ±: .0415 



The analysis of the drj' cerium sulphate gave results as 

 follows. In a fourth column I show the amount of CeO, 

 proportional to 100 parts of BaS04 • 



* Ann. Chem. Pharm., 42, 134. 



