340 THE ATOMIC WEIGHTS, 



CO. r CeO,. 



48.256 



48.249 



48.248 



48.257 



48.257 



48.258 63417 

 48.257 63.436 

 48.262 63.446 



48.249 63.429 

 48.253 63.430 



Mean, 48.2546 .001 Mean, 63.4316, =b .0032 



These results could not be appreciably affected by combination with 

 the single oxalate experiments of Jegel and of Rarnmelsberg, and the 

 latter may therefore be ignored. 



Robinson's work, published in 1884,* was based upon pure cerium 

 chloride, prepared by heating dry cerium oxalate in a stream of dry, 

 gaseous hydrochloric acid. This compound was titrated with standard 

 solutions of pure silver, prepared according to Stas, and these were 

 weighed, not measured. In the third column I give the ratio between 

 CeCl 3 and 100 parts of silver : 



CeCl 3 . Ag. Ratio. 



5.5361 7.26630 76.189 



6.0791 7-98377 76 172 



6.4761 8.50626 76.133 



6.98825 9.18029 76.122 



6.6873 8.78015 76.164 



7.0077 9.20156 76.158 



6.9600 9- r 393 76.150 



Mean 



Reduced to a vacuum this becomes 76.167. 



In a later paper, f Robinson discusses the color of eerie oxide, and 

 criticises the work of Wolf. He shows that the pure oxide is not white, 

 and makes it appear probable that Wolf's materials were contaminated 

 with compounds of lanthanum. He also urges that Wolf's cerium sul- 

 phate could not have been absolutely definite, because of defects in the 

 method by which it was dehydrated. 



Brauner,J in 1885, investigated cerium sulphate with extreme care, 

 and appears to have obtained material free from all other earths and 

 absolutely homogeneous. The anhydrous salt was calcined with all 



* Chemical News, 50, 251. Nov. 28, 1884. Proc. Roy. Soc., 37, 150. 

 t Chemical News, 54, 229. 1886. 

 t Sitzungs. Wien. Akad., Bd. 92. July, 1885. 



