ATOMIC WEIGHTS 



165 



In a second series of experiments the copper was deposited from solu- 

 tions saturated with cuprous sulphate: 



Weight Cu. Weight Ag. 



.71847 2.43935 



.71861 2.43940 



.72019 2.44603 



.97193 

 .50916 

 .76188 



3.30100 

 1.72859 

 2.58664 



Ratio. 

 339.52 

 339.46 

 339.64 

 339.63 

 339.50 

 339.51 



Mean, 339.543, ± .0200 

 Hence Cu = 63.544. 



In the foregoing series the temperature of the solution was 0°. Two 

 experiments at higher temperatures, 56°-61°, gave lower values for the 

 ratio, and consequently a higher atomic weight for copper : 

 Weight Cu. Weight Ag. Ratio. 



.97295 3.30100 339.28 



.70214 2.58664 339.39 



Mean, 339.335, ± .0370 

 Hence Cu = 63.569. 



There is also an electrochemical series of determinations by Gallo,' of 

 slight importance. The figures with vacuum weights are — ■ 

 Weight Cu. Weight Ag. Ratio. 



.21805 .73937 339.083 



.27153 .92062 339.049 



.19001 .64571 339.829 



.39585 1.34578 339.972 



Mean, 339.483, ± .164 



Hence Cu = 63.555. 



The general combination of all the data relative to the copper-silver 

 ratio is as follows : 



Richards, first series, corrected 339.408, 



Richards, second series 339.404, 



Richards, CuBr^ series 339.392, 



Richards, Collins, and Heimrod, first 339.615, 



Richards, Collins, and Heimrod, second 339.543, 



Richards, Collins and Heimrod, third 339.335, 



Rayleigh and Sidgewick 340.561, 



Gray, large plates 340.935, 



Gray, small plates 339.953, 



Shaw 339.983, 



Vanni 340.406, 



Gallo 339.483, 



General mean 339.423, 



1 Atti Acad. Lincei (5), 14, 23. 1905. 



.0114 

 .0046 

 .0108 

 .0230 

 .0200 

 .0370 

 .0935 

 .1072 

 .0521 

 .0411 

 .0520 

 .1640 



.0038 



