118 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



In solutions of electrolytes in water which exhibit a positive viscosity 

 effect, the conductance appears to change less than the viscosity of the 

 solution. If we treat the conductance curve of lithium chloride in a 

 manner similar to that employed in the case of potassium iodide, we 

 obtain as plot not a straight line, but a curve lying below the straight 

 line resulting from Equation 9a. In other words, the conductance values 

 appear to be overcorrected. This result is illustrated in Figure 17, upper 

 curve, in which A is the uncorrected curve, B is the curve in which the 

 conductance is corrected in direct proportion to the fluidity change, 

 while C is a curve in which correction has been applied to the lithium 

 ion only. We may conclude, therefore, that, in aqueous solutions, the 

 conductance may be corrected for the viscosity change in direct propor- 

 tion to the fluidity change in the case of salts which exhibit a negative 

 viscosity effect, but that, in solutions of salts which exhibit a positive 

 viscosity effect, the correction made should be smaller. Just what cor- 

 rections should be applied is difficult to determine at the present time. 



We have seen that in non-aqueous solutions the viscosity effect is 

 much larger than it is in aqueous solutions. We should therefore expect 

 that the conductance of non-aqueous solutions would be affected to a 

 much greater extent than that of aqueous solutions. It appears, how- 

 ever, that in solutions of electrolytes in non-aqueous solvents the con- 

 ductance changes much less than the fluidity of the solvent. 



The relation between the conductance and the viscosity is illustrated 

 in Figure 19, in which are plotted the conductance and fluidity values 

 of solutions of potassium iodide in liquid ammonia at different concen- 

 trations. Branch B is extrapolated on the assumption that Equation 9a 

 holds. There is also indicated on this figure the calculated conductance 

 of these solutions, Branch D, on the assumption that the conductance 

 changes in direct proportion to the fluidity of the solvent. It will be 

 observed that the conductance, as corrected in this way, is much too low 

 to correspond with the experimental conductance curve represented by 

 circles. It is evident, therefore, that in non-aqueous solutions the con- 

 ductance change is smaller than corresponds to the viscosity change. 

 This is further borne out by the fact that Equation 11 appears to hold 

 for solutions of many electrolytes up to concentrations at times as high 

 as 2 normal. It is obvious that the viscosity of the solutions at these 

 concentrations must be much greater than that of the pure solvent, and 

 consequently it follows that the correction to be applied for the viscosity 

 change is probably the smaller the greater the viscosity change; that is, 

 the lower the dielectric constant of the solvent. On the other hand, it 

 has been found, in the case of all solutions in non-aqueous solvents, that, 



