86 F. E. Beach — Use of Cupric Nitrate in the Voltameter, 



It is natural to inquire how the values found agree with the 

 equivalent calculated from the atomic weight of copper. 



The last named quantity has been investigated with great 

 care by T. W. Richards'* with the following result : 



If silver be taken as 108*00, oxygen as 16*000 and bromine 

 80*007 



From Cu:2Ag he finds Cu = 63-640 



Cu: (2AgBr) Cu = 63*648 



CuBr : 2A2 Cu = 63*643 



Cu = 63-644 



whence we get 



Cu 



2Ag 



= 0-29465 



and Cu Equivalent = 0*00032944 

 when silver is taken = 0-0011181 



Hence the value here found is substantially in accord with 

 Richards'. In making this comparison it must be borne in 

 mind that the present investigation was not undertaken for the 

 purpose of finding the equivalent of copper but to determine 

 how well the nitrate would serve as the electrolyte in the 

 copper voltameter and that too, throughout a considerable 

 range of conditions. That these conditions when working 

 with such a sensitive metal as copper were sometimes unfavor- 

 able to uniformity of result may be sufficient to explain the 

 amount of variation from the mean. The probable error of a 

 single observation in the Second Series is rh 1*9. 



Further experiments were tried to determine the effect of 

 variations in the temperature. Here again it is to be remem- 

 bered that the solutions were not freshly prepared. A con- 

 siderable change of temperature either up or down seemed to 

 favor oxidation, but more particularly the latter, probably on 

 account of the increase in concentration of the salt when 

 cooled. Still even this was in great measure prevented by a 

 sufficient addition of the ammonium chloride. 



No. 



Solution. 



Temperature. 



KquivaleE 



56 



Cu2NO, with NH 4 Cl 



19° 



3296 



57 



Same 



6 



3297 



58 



Same 



34 



3292 



59 



Same 



29 



3321 



60 



Another solution 



18 



3291 



61 



Same 



36 



3297 



62 



Same 



37 



3296 



63 



Same 



6 



3313 



64 



Same 



10 



3307 



65 



A different solution 



40 



3291 



66 



Same 



10 



3292 



Proc. Amer. Acad., xxiii, p. 111. Ibid , xxv, p. 21 



