54 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



that this relation is fulfilled in the case of aqueous solutions of weak acids 

 and bases, but is not fulfilled in the case of solutions of electrolytes which 

 are more largely ionized. 



It is at once apparent that non-aqueous solutions furnish exceptions 

 to the simple mass-action law, since we have here cases in which the 

 conductance increases with increasing concentration, which result is not 

 in accord with Equation 7. To solve the problem resulting from this 

 discrepancy, three methods of attack at once present themselves. In the 

 first place, the ionization may not be correctly measured by the ratio 

 A/A . Then, again, we may assume that the reaction equation on which 

 the calculations are based is not correct. Finally, we may assume that 

 the equilibrium is of the type as assumed, but the conditions assumed 

 in deriving the mass- action law are not fulfilled in the solutions in ques- 

 tion; in other words, the solutions may not be considered as dilute. It 

 is of course impossible to state on a priori grounds the concentration at 

 which the deviations from the laws of dilute solutions will become appre- 

 ciable. The only method that we have of attacking this problem at 

 present is to carry out measurements at different concentrations and 

 examine the change in the mass-action function as the concentration de- 

 creases. If the fundamental assumption underlying the hypothesis of 

 Arrhenius is correct, then the mass-action function should approach a 

 definite limiting value as the concentration decreases. 



Let us examine, therefore, the conductance curves of the more dilute 

 non-aqueous solutions in order to determine whether the mass-action 

 function approaches a definite limiting value. It is obvious that, in order 

 to calculate the degree of ionization, the value of A must be known and 

 this value can be obtained only by extrapolation. If the mass-action 

 equation in its simple form actually holds, then it is possible to determine 

 the value of A by a very simple graphical extrapolation. Equation 7 

 may be written in the form: 



(8) 



It is obvious that, if this equation holds, the reciprocal of the equivalent 

 conductance, A, is a linear function of CA, which is equal to the specific 

 conductance multiplied by 10 3 . In other words, if the mass-action law 

 is obeyed, the reciprocal of the equivalent conductance and the specific 

 conductance are connected by means of a linear equation. If, therefore, 

 the experimental values of CA and of I/A are plotted in a system of rec- 

 tangular co-ordinates, the points will lie on a straight line if the mass- 

 action law holds. This straight line extrapolated to the axis of I/A 



