ATOMIC WEIGHTS 301 



Neglecting the work of Chydenius, which has no present value, we 

 have six ratios from which to deduce the atomic weight of thorium, as 

 follows : 



(1). 2BaSO,:ThO,: :100:58.026, ± .214 



(2). 2BaS04:Th(S04)„.4H„0: :100:107.509, ± .585 



(3). 4CO,:ThO,: :100:151.114, ± .053 



(4). Th ( SO,), . 9HoO : ThO„ :: 100: 45.090, ± .0019 



(5). Th(S04),.4H,0:ThO,: :100:52.535, ± .0473 



(6). ThCSOJ.iThO,: :100:62.296, ± .0007 



To reduce these ratios we have — 



S =32.0067, ±.00075 Ba =137.363, ±.0025 



C = 12.0038, ± .0002 H = 1.00779. ± .00001 



Hence, 



From ratio 2 Th = 226.295, ± 2.7311 



" 5 228.998, ± .3451 



" 6 232.579, ± .0063 



" 4 232.639, ± .0145 



" 3 233.983, ± .0933 



" 1 238.900, ± .9998 



Three of these values, the first two and the last, are absolutely worth- 

 less, and can be rejected at once. To include them would not appreciably 

 affect the final combination. The values from ratios 3, 4 and 6, com- 

 bined, give a general mean Th = 332. 598, ±.0058, or 332.6 rounded off. 



In this discussion the question of the definite individuality of thorium 

 has not been touched. Eecent investigations upon radioactivity have 

 shown that the supposed element may be really complex, or at least that 

 it contains traces of other substances. Baskerville ^ and Brauner ^ have 

 both claimed to have fractionated thoria into different component earths, 

 which differed widely in atomic weight and physical properties. These 

 claims, however, are not as yet fully substantiated. Meyer and Gumperz 

 believe that their atomic weight determinations establish the integrity 

 of thorium; but the question is still open. Much work remains to be 

 done before the controversy can be declared ended. Meanwhile tiie 

 atomic weight as given above represents that of the thorium which is 

 recognized as an element by all analysts. 



iJourn. Amer. Chem. Soc, 23, 761 and 26. 922. 

 2 Proc. Chem. Soc, 17, 67. 

 20 



