LEAD. BERZELIL'S. 77 



cgr. when using a matrass with very long neck. These 

 results were first published by him in 1810. (Sebelien, 



P- M3)- 



Per unit we get the analytical ratio 1.07 750 (where we 

 have to supply the last decimal not determined) which is 20 

 high. 



The actual determinations to the fourth place, which 

 really is uncertain, since Berzelius weighed to the centi- 

 gramme only which represents the third place in our ratio 

 (centigramme to 10 grammes is milligramme to the gramme, 

 or third place in our ratio per unit). 



In other words, Berzelius found the oxide exceeding the 

 amount calculated from the standard atomic weight only 

 two centigrammes in excess on ten grammes of lead ; that is, 

 only two units of his smallest weights used on his balance. 



These are in point of time, the earliest of all atomic 

 weight determinations of any heavy metal ; they differ from 

 the calculated standard by only two units in a thousand. 



C. Lead Oxide, Dry Way. Earliest Work. 



In 1812 he published in the Swedish Afhandlingar (vol. 

 V, see Sebelien p. 143) his first reductions of pure lead oxide 

 to metallic lead by heating the oxide in a current of dry 

 hydrogen gas. 



This is a chemical process of a much higher degree of 

 accuracy, and accordingly we find that his determinations 

 came much nearer our atomic ratio. 



His three determinations, referred to a unit weight of 

 lead, gave 1.07 722; 1.07 723 and 1.07 740 as analytical ratios. 



These ratios are, in the order given, 8 low, 7 low and 

 10 high, when compared to our atomic ratio above given, 

 namely 1.07 730. 



The mean of* his three determinations is 1.07 728 which is 

 only 2 low (in 5th place) in comparison with our atomic ratio. 



If we were tc consider his determinations exact to the 

 fifth place of the analytical ratio, the atomic weight would 

 be I or of one tenth, that is 0.03 lower than the standard 

 207, that is 206.97. 



