OTHER PROPERTIES OF ELECTROLYTIC SOLUTIONS 301 



c u 



that, on the other hand, the calculated values of the ratio -~^ differ 



enormously from those measured. The value of the ratio -^, as deter- 



L u* 



mined from conductance measurements, may be somewhat in error 

 owing to uncertainties in the value of A . Since the value of 1 y is 

 relatively small, it is obvious that a small error in the value of A 

 will have a large effect on the value of the ratio determined from 

 conductance measurements. Nevertheless, it is evident that the electro- 

 motive force as measured is much greater than that calculated according 

 to Equation 95. 



In the case of other electrolytes similar results have been obtained. 



C- 

 In the following table are given values of -^ as calculated from the 



t2 



electromotive force of potassium chloride concentration cells. 27 The 

 concentrations of the solutions are given in the first two columns, the 

 values found and calculated for the ion ratios are given in the last two 

 columns. 



TABLE CXXV, 



C ' 

 COMPARISON OF THE RATIO -^, AS DETERMINED FROM ELECTROMOTIVE 



% 

 FORCE AND CONDUCTANCE MEASUREMENTS. 



C ' C- 



0.5 0.05 8.85 8.09 



0.1 0.01 9.16 8.33 



0.05 0.005 9.30 8.64 



0.01 0.001 9.62 9.04 



It is evident that the ion ratios as determined by means of conductance 

 measurements are considerably greater than those calculated from the 

 measured electromotive forces, assuming Equation 95 to hold. As the 

 solutions become more dilute, the two values approach each other slowly. 

 The explanation of these phenomena has been the subject of much 

 discussion. The observed fact is that, assuming the laws of dilute 

 solutions to hold, the electromotive force of a concentration cell as 



"Maclnnes and Parker, J. Am. Chem. Soc. S7, 1445 (1915). 



