336 THE ATOMIC WEIGHTS. 



In 1848 similar figures were publislied by Marignac,* who found the 

 following amounts of BaSO^ proi^ortional to 100 of dry cerium sulphate : 



122.68 

 122. OO 

 122.51 



Mean, 122.40, zb .138 



If we give Hermann's single result the weight of one experiment in 

 this series, and combine, we get a mean value of 122.856, ± .130. 



Still another method was employed by Marignac. A definite mixture 

 was made of solutions of cerium sulphate and barium chloride. To this 

 were added, volumetrically, solutions of each salt successively, until 

 equilibrium was attained. The figures published give maxima and 

 minima for the BaClj proportional to each lot of Ce^CSOJg. In another 

 column, using the mean value for BaCl^ in each case, I put the ratio 

 between 100 parts of this salt and the equivalent quantity of sulphate. 

 The latter compound was several times recrystallized : 



Ce.,{SO^),. Baa,. Ratio. 



First crystallization Il.oiigrm. ir.990 — 12.050 grm. 91.606 



First crystallization 13-194 " 14-365 — 14-425 " 91-657 



Second crystallization 13-961 " 15.225 — 15.285 " 9I-518 



Second crystallization.. . . 12.627 " 13-761 — 13.821 " 91.559 



Second crystallization... . 11.915 " 12.970 — 13.030 " 91.654 



Third crystallization 14.888 " 16.223 — 16.283 " 9I-602 



Third crystallization 14-I13 " 15-383—15-423 " 91-755 



Fourth crystallization.. . . 13. ill " 14.270—14.330 " 91.685 



Fourth crystallization 13.970 " 15.223 — 15.283 " 91.588 



Mean, 91.625, zb .016 



Omitting the valueless experiments of Kjerulf,t we come next to the 

 figures published by Bunsen and Jegel ;|: in 1858. From the air-dried 

 sulphate of cerium the metal was precijjitated as oxalate, which, ignited, 

 gave CeO.^. In the filtrate from the oxalate the sulphuric acid was esti- 

 mated as BaSO^ : 



1.5726 grm. sulphate gave .7899 grm. CeOj and 1. 6185 grm. BaSO^. 

 1.6967 " .8504 " I-7500 " 



Hence, for 100 parts BaSO^, the CeO^ is as follows : 



48.804 

 48-575 



Mean, 48.689, zb .077 



* Arch. Sci. Phys. et Nat. (i), 8, 273. 



t Ann. Cheni. Pharni., 87, 12. 



\ Ann. Chem. Pharni., 105, 45. 1S58. 



