ATOMIC WEIGHTS 385 



From the solutions 0.0002 gramme of silver was recovered, to be added 

 to the sum of the silver weights given above. This raises the percentage 

 to 62.9193. Hence 86 = 79.155. 



Combining Meyer's series with its predecessors we have — 



Ekman and Pettersson 62.957, ± .0048 



Lenher 62.895, ± .0014 



Meyer 62.9193, ± .0082 



General mean 62.9003, ± .0013 



There are now eight ratios from which to deduce the atomic weight 

 of selenium : 



(1). SeOotSe:: 100: 71.1907, ±.0016 

 (2). BaSeOsrBaSO^: : 100: 88.437, ± .013 

 (3). HgSe:Hg: : 100: 71.7327, ± .003 

 (4). Se:4Cl::100:178.696, ±.125 

 (5). AgoSeOj : 2 Ag :: 100: 62.9003, ± .0013 

 (6). Ag2Se03:2AgCl: : 100: 83.5.58, ± .0017 

 (7). Am2SeBre:Se:: 100: 13.3224, ± .0017 

 ( 8 ) . CjoHioSe : 1200^ :: 100 : 226.536, ± .0486 



The atomic weights used in reducing these ratios are as follows : 



Ag = 107.880, ± .00029 C = 12.0038, ± .0002 



CI = 35.4584, ± .0002 Ba = 137.363, ± .0025 



Br = 79.9197, ± .0003 Hg = 200.054, ± .0017 



N = 14.0101, ± .0001 H = 1.00779, ± .00001 



Hence, 



From ratio 2 Se = 78.587, ± .0388 



" 3 78.883, ± .0124 



" 8 78.972, ± .0501 



" 1 79.075, ± .0047 



" 7 79.248, ± .0102 



" 5 79.259, ± .0052 



" 6 79.328, ± .0070 



" 4 79.373, ± .0555 



General mean, Se = 79.176, ± .0029 



This mean is slightly lower than the values obtained by Lenher, but 

 near that given by Meyer. In default of more evidence it seems to be 

 as trustworthy as any value which might be arbitrarily chosen. 



