LEAD. 131 



We have now nine ratios from which to compute : 



(i.) Per cent, of Pb in PbO, 92.8271, .0013 

 (2.) Per cent of PbO in PbN 2 O 6 , 67.4027, .0016 

 (3.) Pb : PbSO 4 : : 100 : 146.4262, .0023 

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

 (5.) PbSO 4 : PbN 2 O 6 : : 100 : 109.307, .0020 

 (6.) Pb : PbN 2 O 6 : : iqo : 159.9704, .0010 

 (7.) Pb : PbC) 2 : : 100 : 134.191, .013 

 (8.) PbCl 2 : 2AgCl : : 100 : 103.21, .0745 

 (9.) Ag 2 : PbCl 2 : : 100 : 128.7266, db .0130 



To reduce these ratios we must use the following data : 



O =. 15.879, .0003 s = 31.828, .0015 



Ag= 107.108, =b .0031 N 13.935,^.0021 



Cl == 35.179, db .0048 AgCl= 142.287, .0037 



For the molecular weight of lead oxide we now get three estimates : 



From (i) PbO = 221.375, d= .0403 



From (2) " 221.796, .0132 



From (4) " = 221.944, d= .1116 



General mean PbO = 221.757, =b .0125 



For lead chloride we have 



From (8) PbCl 2 = 275.723, .1989 



From (9) " = 275.753,^.0290 



General mean PbO 2 = 275.752, dr .0287 



Including these results, six values are calculable for the atomic weight 

 of lead : 



From molecular weight of PbO Pb = 205.878, dr .0126 



From molecular weight of PbCl 2 " = 205.394, .0302 



From (3) " = 205.367, dr .0051 



From (5) " = 203.352, .0479 



From (6) " = 205.341, db .0068 



From (7) " = 205.779, .0831 



General mean Pb = 205.395, .0038 



If = 16, Pb = 206.960. If we reject the first, fourth, and sixth of 

 these values, which are untrustworthy, the remaining second, third, and 

 fifth give a general mean of Pb = 205.358, .0040. If O = 16, this 

 becomes Pb = 206.923. From Stas' ratios alone Stas calculates Pb = 

 206.918 to 206.934 ; Ostwald finds 206.911 ; Van der Plaats (A), 206.9089, 

 (B), 206.9308, and Thomson 206.9042. The value adopted here repre- 

 sents mainly the work of Stas, and with H = 1 is 



Pb = 205.358, .0040. 



