206 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



Treating both series as one, and reducing the figures to the form of 

 ratio adopted in this work, the mean becomes 



2Ag:Pb: : 100: 95.853. ± .0020 



Combined with the series by Betts and Kern, 95. 814, ±.0097, the gen- 

 eral mean becomes 95. 850, ±.0019. 



The following ratios are now available from which to compute the 

 atomic weight of lead : 



(1). PbOrPb:: 100: 92.8271, ±.0013 

 (2). PbN20e:PbO: : 100: 67.4027, ± .0016 

 (3). Pb:PbSO,: : 100: 146.4262, ± .0023 

 (4). PbO:PbSO,: :100:135.804, ± .0180 

 (5). PbS04:PbN,0„: :100:109.307, ± .0020 

 (6). Pb:PbN„Oe: : 100: 159.9704, ± .0010 

 (7). Pb:PbCl2: :100:134.191, ± .0130 

 (8). 2Ag:PbCU: :100:128.843, ± .0010 

 (9). 2AgCl:PbCL: : 100: 96.977, ± .0039 

 (10). 2Ag:Pb:: 100: 95.850, ±.0019 



Computing with 



Ag =107.880, ± .00029 N =14.0101, ± .0001 



CI = 35.4584, ± .0002 S = 32.0667, ± .00075 



we have — 



From ratio 5 Pb = 204.749, ± .0475 



" 6 206.802, ± .0035 



"10 206.806, ± .0041 



" 3 206.923, ± .0104 



" 1 207.062, ± .0376 



" 8 207.075, ± .0023 



" 9 207.094, ± .0112 



" 2 207.337, ± .0118 



" 7 207.414, ± .0789 



" 4 207.625, ± .1125 



General mean, Pb = 206.970, ± .0017 



The rejection of the first and last two values in this series only raises 

 the general mean to 207.972, and it is therefore immaterial whether 

 they are retained or cast aside. On chemical grounds the values from 

 ratios 8 and 9 are probably the best, but they need additional confirma- 

 tion. The final result is presumably, but not certainly, too low. 



