ATOMIC AVEIGHTS 515 



Cerium oxalate contains water, in proportions whicli are not abso- 

 lutely constant; at least not constant enough for good atomic weight de- 

 terminations. In Buehrig's analyses the water was estimated, but it 

 is doubtful whether the estimations can be made with adequate sharpness. 

 Cerium oxalate, therefore, is best handled by the method of Stolba and 

 Gibbs; which consists in determining the amount of eerie oxide left after 

 calcination; and in another portion of the same sample, estimating the 

 radicle CoOg by titration with potassium permanganate. From the ratio 

 SCoO, : 2CeOo the atomic weight of cerium can be calculated. 



This method was followed by Brauner, in a single determination wliich 

 has already been cited. It was also adopted by Brauner and Batek, who 

 give five sets of determinations, with vacuum weights, as follows. I 

 cite now only the percentages of CeOo and C.O3, as computed from the 

 weighings, together with the required ratio: 



The ratio here is computed from the individual figures for C._.0.. and 

 the mean for CeOo. 



Sample II. 



Per cent. CeO... Per cent. CJ) .. Ratio. 



47.197 29.601 159.353 



47.089 29.564 159.552 



47.225 • 29.559 159.579 



Mean, 47.170 



Samples III, IV. V. 

 Per cent. CeO,. Per cent. C.O.. Ratio. 



in ti'!??;]- 29.512 159.718 



47.160 j 



IV ^?-??? I 29.391 159.654 



46.922 

 V 47.039 29.531 1.59.287 



