LANTHANUM. 349 



weight of lanthanum by the same general method as the preceding 

 Bauer's data * are as follows : 



.6431 grm. La 2 O 3 gave 1.1171 sulphate. 57.569 per cent. 



.7825 " 1.3613 " 57.482 " 



1.0112 " I.757I " 57-549 " 



.7325 " 1.2725 " 57.564 " 



Mean, 57.541, =b .0136 



Bettendorff found f- 



.9146 grm. La 2 O 3 gave 1.5900 sulphate. 57-522 per cent. 



-9395 " '.6332 " 57.525 " 



.9133 " I-5877 " 57.523 " 



1.0651 1.8515 " 57.526 " 



Mean, 57.524, .0006 



We may now combine the similar means into general means, and de- 

 duce a value for the atomic weight of lanthanum. For the percentage of 

 oxide in sulphate we have estimates as follows. The single experiments 

 of Czudnowicz and of Erk are assigned the probable error and weight of 

 a single experiment in Hermann's series : 



Czudnowicz 58.668, =b .027 



Erk 57.o68, .027 



Hermann 57-654, rfc .016 



Zschiesche 57-O2I, .051 



Marignac 57-5475, .01 15 



Cleve, earlier series 57-6i9, .0085 



Cleve, later series 57-48o, .0040 



Brauner, earlier series 57-5575, =b - OI ! 5 



Brauner, later series 57.480, .0084 



Bauer 57-541, db .0136 



Bettendorff. 57-524, .0006 



General mean 57.522, .00059 



This result is practically identical with that of Bettendorff, whose work 

 seems to receive excessive weight. The figure, however, cannot be far 

 out of the way. 



For the quantity of La 2 (S0 4 ) 3 proportional to 100 parts of BaSO 4 . we 

 have five experiments, which may be given equal weight and averaged 

 together : 



Marignac , 81.022 



Marignac 80.934 



Rammelsberg 79.276 



Czudnowicz 79. 1 1 7 



Erk 79.921 



Mean, 80.054, .270 



* Freiburg Inaugural Dissertation, 1884. 

 i Ann. d. Chem., 256, 168. 



