372 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



follows that the negative carrier in all metals is the same. If this is 

 true, and if the negative carrier in the solutions of the alkali metals in 

 ammonia' is the negative electron, then those properties of these solu- 

 tions which depend upon the negative carrier should be the same in 

 solutions of different metals. In how far this is true we shall see pres- 

 ently, since many of the properties of these solutions have been analyzed 

 in terms of their ionic constituents. 



Since the solutions of the metals in ammonia are ionized, the prob- 

 lem of determining the nature of the conduction process may be attacked 

 in a manner similar to that employed in the case of ordinary electrolytic 

 solutions. It is possible, in the first place, to determine the relative 

 amount of the current carried by the two ions under given conditions. 

 For this purpose, transference measurements might be carried out', the 

 concentration changes resulting when a given quantity of electricity 

 passes through the solution being determined. This experiment is diffi- 

 cult of execution, and consequently recourse has been had to another 

 method, the results of which, although they are not as conclusive as 

 direct transference determinations, nevertheless make it possible to 

 determine the general order of magnitude of the quantities involved. The 

 electromotive force of a concentration cell with liquid junction is given 

 by the equation: 



from which the value of n, the transference number, may be determined, 

 if the electromotive force E and the concentrations C YI and C 2 J 2 are 

 known and if the laws of dilute solutions are applicable. Judging by the 

 results obtained in solutions of ordinary electrolytes, this equation yields 

 results which are approximately correct. In the case of a concentration 

 cell which consists of two platinum electrodes placed in metal solutions, 

 having concentrations C and C 2 , the work is due to the transfer of n 

 mols of sodium per equivalent of electricity from the concentration C x 

 to the lower concentration C 2 . The cell is similar to that of a salt solu- 

 tion with reversible anodes, n is obviously the fraction of the current 

 transported by the positive carrier in the solutions. 



In Table CXLIX are given values of the electromotive force of con- 

 centration cells at different concentrations the rdtio of the concentra- 

 tions of the two solutions was approximately 1:2 together with the 



transference number n of the cation and the ratio n . 



n 



