ATOMIC WEIGHTS 



277 



The ratios to be considered are now as follows : 



( 1 ) . BaSO, : T1,S04 : : 100 : 216.754, ± .1387 

 ( 2 ) . AgCl : TlCl : : 100 : 166.948, ± .0610 

 ( 3 ) . Agl : Til : : 100 : 140.648, ± .016 

 (4). T1:T1N03: : 100: 130.391, it .00034 

 (5). TLS0,:2T1: :100:80.953, ± .0030 

 (6). TL03:2T1: : 100: 89.481, ± .0040 

 (7). 2T1N03:TL03:: 100: 85.713 

 ( 8 ) . TI2SO4 : TLO3 : : 100 : 90.465, ±: .0020 

 (9). Tlj03:3H„0: : 100: 11.837, ± .0029 



The antecedent atomic wei2:hts are as follows ; 



Ag = 107.880, ± .00029 

 CI = 35.4584, ± .0002 

 I = 126.9204, ± .00033 



N =14.0101, ± .0001 

 S = 32.0667, ± .00075 

 H = 1.00779, ± .00001 



Eatio 7 rests npon a single experiment, and the atomic weight derived 

 from it must therefore be arbitrarily weighted. To do this its probable 

 error is assumed to be the same as that given by ratio 8. Taking so 

 much for granted, the nine values for thallium are 



From ratio 3 Tl = 203.322, di .0376 



" 2 203.842, ± .0875 



" 8 204.021, It .0695 



" 7 204.037, It .0695 



" 4 204.041, It .0023 



" 5 204.150, ± .0330 



" 6 204.158, It .0780 



" 9 204.300, ± .0593 



" 1 204.950, It .1619 



A glance at the " probable errors " in this series of values will show 

 that Crookes' ratio, No. 4, carries overwhelming weight. It is therefore 

 unnecessary to compute the general mean, for it could not vary much 

 from that. The value Tl = 204.04 is to be accepted as the best. 



