COPPER. 



99 



Vanni. 

 340.483 

 340.600 



340.367 

 340.252 

 340.600 

 340.136 



340.406, 

 .0520 





The lack of sharp concordance in these data and the consequently 

 high probable errors seem to indicate a distinct superiority of the purely 

 chemical method of determination over that adopted by the physicist. 

 The eight distinct series now combine as follows : 



Richards, first series corrected 339-48, .0114 



Richards, second series ... 339.404, .0046 



Richards, CuBr 2 series . 339.392, =b .0108 



Rayleigh and Sidgewick 340.561, d= .0935 



Gray, with large plates 34-935, ^ . 1072 



Gray, with small plates 339-953, .0521 



Shaw . .. 339.983, =b .0411 



Vanni 340.406, .0520 



General mean 339-41 1, .0039 



If we combine Richards' three series into a general mean separately, 

 we get 339.402, .0040. Hence the other determinations, having high 

 >robable errors, practically vanish from the result, and it is a matter of 

 idifference whether they are retained or rejected. 



We now have the following ratios from which to compute the atomic 

 .'eight of copper : 



(i.) Percentage of Cu in CuO 79-8355, .0010 



(2.) 



(3-) 

 (4.) 



(5.) Cu 

 (6.) Cu 



of Cu in CuSO 4 39-795, =fc -0036 



of Cu in CuSO 4 , 5H 2 O. . 25.451, .0011 

 of CuO in CuSO 4 49-8i6, ^-.0017 



Na,CO, 



Na 2 SO 4 : 



100 



IOO 



166.838, .0035 



223.525, =fc .0098 

 (7.) BaSO 4 : Cu : : 93- 28 9 : 25-448- 

 (8.) 2AgBr : Cu : : IOO : 16.924, .0007 



(9- 



: Ag 2 



.0039 



