98 



THE ATOxMIC WEIGHTS, 



alent proportions. In the first paper the following results were detained. 

 The third column o-ivos the value of x in the ratio Cu : Ag, : : 100 : .r. 



.01 14 



In the second ])aper Richards states tliat the silver of the fifth experi- 

 ment, which had been dried at 150°, as were also the others, still retained 

 water, to the extent of four-tenths milligramme in two grammes. If we 

 assume this correction to l)e fairly uniform, as the concordance of the 

 series indicates, and apply it throuuhout, the mean value for the ratio 

 then becomes 389.408, ± .0114. This procedure, however, leaves the 

 ratio in some uncertainty, and accordingly some new determinations 

 were made, in which the silver, collected in a Gooch crucible, was heated 

 to incipient redness before final weighing. Copper from two distinct 

 sources was taken, and three exjieriments were carried out upon one 

 sample to two with the other. Treating both sets as one series, the 

 results were as follows : 



.0046 



a value practically identical with tlie corrected mean of the previous 

 determinations, and with that found in the later experiments upon 

 copper bromide. 



In various electrical investigations the same ratio, the electrochemical 

 equivalent of copper, ha.s been repeatedly measured, and the later results 

 of Lord Rayleigh and Mrs. Sidgewick.-'^ Gray,t Shaw, % and Vanni § ma}^ 

 properly be included in this discussion. As the data are somewluit dif- 

 ferently stated, I have reduced them all to the common standard adopted 

 above. Gray gives two sets of measurements, one made with large and 

 the other with small metallic plates : 



* Phil. Trans.. 175, 458. 



tPhil. Mag. (5), 22, 389. 



J British Assoc. Report, 1886. Ab.stract in Phil. Mag. (5), 23, 138. 



§ Ann. der Phys. (Wiedemann's) (2), 44, 214. 



