34 



derived the concentration of copper ions present in any 

 solution containing only Cu(NC2)2, but no published data 

 are yet available from which might be ascertained the con- 

 centrations of copper ions in the binary mixtures here 

 dealt with. 



The determinations here required of the relative 

 concentrations of copper ions in solutions of Gu(NC3)2 

 with and without addition of the calcium salt, may be 

 made by means of the potentiometer ^^ . With this ins- 

 trviment the solutions involved in the table given on 

 page 26 were tested and the differences in electrical 

 potential between the combination solutions of Cu(NC2)2 

 and Ca(NC3)2 and the corresponding simple solutions of 

 Cu(R03)2 were measured. The two solutions to be tested 



15. Loomis, K. E. , and Acree, 3. F. , A study of the 

 hydrogen electrode, of the calomel electrode, and of 

 contact potential. Araer. Chem. Journ. 46:585-620. 



16. It is a pleasure to acknowledge here, that the sug- 

 gestion of this method as applicable to the problem in 

 hand is due to Professor S. F. Acree, of the Chemistry 

 Department of this University, and that much valuable 

 help in making the determinations was received from him 

 and from Dr. C. N. Myers. This part of the work was 

 carried out at the Chem istry Laboratory. 



