LANTHANUM. 229 



From molecular weight of CeOj Ce ^= 139.563, ± .024 



Cej(S0«)3 " == 141. 281, =b .083 



From ratio (7,) CO^ in oxalate " = 141.228, zb .025 



General mean " == 140.424, zt .017 



Or, if O = 16, Ce = 140.747. 



Buehrig's results alone, both sets combined, give Ce = 

 141.198, ± .020 ; or, if = 16, Ce = 141.523. 



Wolf and Wing's figures alone make Ce = 137.724 ; or, if 

 O = 16, Ce = 138.039. 



The latter result is subject to the errors pointed out by 

 Buehrig as involved in the use of cerium sulphate; but the 

 ceroso-ceric oxide obtained in the anal,yses was pure white. 

 Buehrig's ceroso-ceric oxide, on the other hand, was yellow. 

 In neither case was didymium present. All things consid- 

 ered, therefore, it is probable that the lower result is too low 

 and the higher result too high. How near the general 

 mean of all may be to the truth we have no evidence to 

 show. It is clear that new determinations are needed, made 

 with material yielding white ceroso-ceric oxide, and with 

 avoidance of the sources of error which Buehrig pointed 

 out. 



LANTHANUM. 



Leaving out of account the work of Mosander, and the 

 valueless experiments of Choubine, we may consider the 

 estimates of the atomic weight of lanthanum which are due 

 to Hermann, Rammelsberg, Marignac, Czudnowicz, Holz- 

 mann, Zschiesche, Erk, and Cleve. 



From Rammelsberg* we have but one analysis. .700 

 grm. of lanthanum sulphate gave .883 grm. of barium sul- 

 phate. Hence 100 parts of BaSO^ are equivalent to 79.276 

 of La^lSOJg. 



■* Poggend. Anna!., 55, 65. 



