ATOMIC WEIGHTS 201 



35.84 

 35.71 

 35.84 

 35.75 

 35.79 

 35.78 

 35.92 



Mean, 35.804, ± .018 



Hence Pb = 207.625. 



These figures are not wholly reliable. Numbers one, two and three 

 represent lead oxide contaminated with traces of nitrate. The oxide of 

 four, five and six contained traces of minium. Number seven was free 

 from these sources of error, and, therefore, deserves more consideration. 

 The series as a whole undoubtedly gives too low a figure, and this error 

 would tend to slightly raise the atomic weight of lead. 



Still a third series by Turner establishes the ratio between the nitrate 

 and the sulphate, a known weight of the former being in each experi- 

 ment converted into the latter. One hundred parts of sulphate represent 

 of nitrate : 



109.312 



109.310 



109.300 



Mean, 109.307, ± .002 



Hence Pb = 204.75. 



In all these experiments by Turner the necessary corrections were 

 made for weighing in air. 



In 1846 Marignac ^ published two sets of determinations of only 

 moderate value. First, chlorine was conducted over weighed lead, and 

 the amount of chloride so formed was determined. The lead chloride 

 was fused before weighing. The ratio to 100 Pb is given in the last 

 column : 



20.506 grm. Pb gave 27.517 PbCL. 134.190 



1C.281 " 21.858 " 134.225 



25.454 " 34.149 " 134.159 



Mean, 134.191, zt .013 



Hence Pb = 207.41. 



Secondly, lead chloride was precipitated by silver nitrate and the 

 ratio between PbCL and 2AgCl determined. The third column gives the 

 PbCL equivalent to 100 parts of AgCl: 



1 Ann. Chem. Pharm., 59, 2S9 and 290. 1846. Oeuvres Completes, 1, 186. 



