154 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



The older determinations practical!}' vanish, leaving the Eichards and 

 Archibald mean almost unchanged. 



The figures for the bromide series are as follows: 



From Ag ratio, Cs = 132.817. 

 From AgBr ratio, Cs= 132.818. 

 And Ag: Br:: 100:74.078. 



When caesium nitrate is fused with finely powdered silica, caesium 

 silicate is formed, and the elements of the nitric radicle are expelled. 

 With weighed quantities of the nitrate, the loss of weight is equivalent 

 to NsOs- The ratio ISToOg : Cs„0 : : 100 : x is thus easily determined. In 

 four experiments Richards and Archibald obtained the following results: 



Mean, 260.693, ± .0039 

 Hence Cs= 132.801. 

 The five ratios for the atomic weight of ca?sium are now as follows: 



(1). AgrCsCl: : 100: 155.9635, ± .0016 

 (2). AgCl:CsCl: : 100: 117.405, ± .0016 

 (3). Ag:CsBr::100:197.198, ± .0045 

 (4). AgBr:CsBr::100:113.279, ±.0007 

 (5). NA:CS20: : 100: 260.693, ± .0039 



Reducing these ratios with 



Ag = 107.880, ± .00029 

 CI = 35.4584, ± .0002 



Br =79.9197, ± .0003 

 N = 14.0101, ±: .0039 



we have- 



Prom ratio 1 Cs = 132.795, ± .0018 



" 5 132.801, ± .0022 



" 3 132.818, ± .0049 



" 4 132.818, ± .0015 



" 2 132.828, ± .0024 



General mean, Cs = 132.811, ± .0010 



