Chapter IV. 

 Form of the Conductance Function. 



1. The Functional Relation between Conductance and Concentra- 

 tion. If an equilibrium exists between the ions and the un-ionized mole- 

 cules in a solution, then the relation between the conductance and the 

 concentration is expressed by Equation 7, which follows from the mass- 

 action law. We have seen that this equation is fulfilled in solutions of 

 weak electrolytes in water and that it is approached as a limiting form 

 in solutions of strong electrolytes in non-aqueous solvents. This equa- 

 tion is the only one so far suggested to account for the relation between 

 the conductance and the concentration which has a substantial theoretical 

 foundation for its support. At higher concentrations, in the case of the 

 stronger electrolytes, both in water and in non-aqueous solvents, the 

 simple form of the mass-action law no longer holds. Except at very 

 high concentrations, where viscosity effects become pronounced, the con- 

 ductance in all cases varies in such a way that the value of the mass- 

 action function increases with increasing concentration. If the reciprocal 

 of the equivalent conductance is plotted against the specific conductance, 

 then, in the case of strong electrolytes, it is found that the experimental 

 curve is concave toward the axis of specific conductances. 



We have seen that in different solvents the conductance curve, as a 

 function of the concentration, varies greatly in form, and the conclusion 

 might be drawn that the process involved in these solutions is entirely 

 different in character. Since the form of the conductance function in 

 the case of the concentrated solutions is thus far not determinable from 

 theoretical considerations, various attempts have been made to deter- 

 mine empirical functions which should express the conductance in terms 

 of the concentration. In the case of aqueous solutions the equation of 

 Storch a appears to apply over a considerable concentration range. This 

 equation may be written in the form: 



where D and m are constants. This equation applies remarkably well 

 in the case of aqueous solutions, even up to high concentrations. It will 



'Storcb, Ztschr. /. pJiyg. Chem. 19, 13 (1896). 



67 



