SYSTEMS INTERMEDIATE 



377 



similar to that of binary electrolytes in liquid ammonia, the only ma- 

 terial difference being that the conductance has a much higher value. 

 The equivalent conductance of the sodium ion is 130. It follows, then, 

 that the equivalent conductance of the negative carrier in these solutions 

 at low concentrations is in the neighborhood of X 886, or 6.8 times that of 

 the sodium ion. We saw in the previous section that the results of 

 measurements of the electromotive force of concentration cells indicate 

 that the carrying capacity of the negative carrier is approximately 7 

 times that of the positive ion in a sodium solution. This value, therefore, 

 is in excellent agreement with the value 6.8 obtained from conductance 



O 

 Q 



l.s 0.0 o.s /.o /.s *& t.s a.o js +.0 *.* 



Log V. 



FIG. 65. Equivalent Conductance of Sodium in Liquid Ammonia at 33.5 at 



Different Concentrations. 



measurements. Evidence has already been presented which indicates 

 that the positive ion in a sodium solution is identical with the positive 

 ion in a solution of a sodium salt. The fact that the conductance of the 

 positive ion, as derived from measurements with the metal solutions, 

 corresponds with that of the sodium ion as derived from measurements 

 with solutions of sodium salts confirms this hypothesis. The positive 

 ion in a solution of sodium in liquid ammonia is therefore the normal 

 sodium ion. 



If, now, we examine the conductance curve in the more concentrated 

 solutions, we see that below a concentration of 0.05 N the conductance 

 increases with the concentration, the increase being the greater the 

 higher the concentration. This, again, confirms the conclusion derived 

 from a study of the electromotive force of concentration cells. As the 

 concentration increases, the relative carrying capacity of the negative 

 carrier increases. The increase in conductance is due to an increase in 

 the mean speed of this carrier, since at higher concentrations the con- 



