LEAD. BERZELIUS. 87 



Only Turner has, in 1833, made determinations of this 

 kind, 7 in number; range 210; mean 70 high. 



The range being three times the extent of the deviation 

 of the mean from the atomic ratio, this process is thereby 

 proved unfit for accurate atomic weight determination. 



It would surely be scientifically incorrect to ascribe the 

 deviation to the atomic weight, while it is evidently due to 

 the lack of precision of the reaction itself. 



The change of " 16 low" for a rise o.i in the atomic 

 weight of lead would indicate the atomic weight 206.6, if the 

 process could be used for such determination. 



The fifth reaction represents the process of ignition of 

 the nitrate. It was carried out 4 times by Anderson in 

 Svanberg's laboratory. Range n, mean 32 high. 



This would require Pb = 206.7 ^ the process were 

 reliable. 



The sixth reaction represents the production of the sul- 

 phate from the metal and the acid. 



Berzelius made 4 determinations. Range 78, mean 42 

 high. 



Turner, 1833, made 3 determinations. Range 55, mean 

 24 high. 



While in these two series of determinations we notice an 

 approach to the atomic ratio, the range is diminishing, we 

 notice in the later determinations by Stas, 6 in number, a 

 diminution of the range to 24 with an increase of the devi- 

 ation to 51 high, corresponding to Pb =: 206.8. 



But at the same time a mere inspection of the individual 

 analytical ratios shows that they systematically change with 

 the amount of lead operated upon. 



Figure 2 on Plate I, facing page 31 of our True Atomic 

 Weights, 1894, shows this fact plainly to the eye. We may 

 also refer to the figure given by us, page 432, T. 116, of the 

 Comptes Rendus for 1893. 



There is absolutely no possibility of denying the fact, 

 that the work of Stas gives analytical ratios systematically 

 varying with the amount of lead used. 



This fact excludes these determinations as chemically 

 unfit. 



