ATOMIC WEIGHTS 



153 



1.5825 grm. CsCl gave 1.351 grm. AgCl. 

 1.3487 " 1.1501 



1.1880 " 1.0141 



1.2309 " 1.051 



Ratio, 117.135 

 117.265 

 117.148 

 117.107 



Mean, 117.164, ± .023 



Hence Cs= 133.483. 



The foregoing investigations may now be regarded as merely pre- 

 liminary, in comparison with the more elaborate determinations made by 

 Richards and Archibald." Their material was purified by fractional 

 crystallization as caesium dichloriodide, from which the chloride, bromide 

 and nitrate were afterwards prepared. The chloride and bromide were 

 freed from possible traces of moisture by fusion in an atmosphere of 

 nitrogen, and analyzed by the usual method. That is, they were pre- 

 cipitated by known weights of silver dissolved as nitrate, and the silver 

 chloride or bromide produced was also weighed. All the weights given 

 are reduced to a vacuum standard. The results obtained with caesium 

 chloride are given in the next table: 



Mean, 117.402, 155.9635, 



± .0016 ±: .0016 



From Ag ratio, Cs = 133.795. 

 From AgCl ratio, Cs = 133.834. 

 And Ag: CI:: 100: 33.846. 



The silver chloride ratio combines with previous determinations thus 



Johnson and Allen 117.499, ± .025 



Bunsen 117.467, ± .013 



Godeffroy 117.164, ± .023 



Richards and Archibald 117.402, ± .0016 



General mean 117.405, ± .0016 



^ Proc. Amer. Acad., 3S, 443. 1903. Zeitsch. anorg-. Chem., 34, 353. 



