Chapter VI. 



The Conductance of Electrolytic Solutions as a Function 



of Temperature. 



1. Form of the Conductance-Temperature Curve. The limiting 

 value of the conductance is a function of the viscosity of the solvent, and 

 consequently of the temperature also. The conductance of the more 

 slowly moving ions is very nearly proportional to the fluidity of the 

 solvent over such ranges of temperature for which viscosity data are 

 available. The conductance of the more rapidly moving ions increases 

 relatively less with the temperature than does that of the more slowly 

 moving ions, and this effect is the more marked the greater the con- 

 ductance of the ions. 



In considering the conductance of solutions at higher concentrations, 

 it is necessary to take into account another factor, namely the change 

 in the ionization of the electrolyte. The observed conductance change is 

 therefore the resultant effect due to the change in the viscosity of the 

 solution and to the change in the ionization of the electrolyte. While, 

 with increasing temperature, the viscosity decreases and the conduct- 

 ance consequently increases, the ionization in general decreases and the 

 conductance of the electrolyte decreases in consequence. Since these two 

 factors affect the conductance in opposite directions, it follows that the 

 resultant effect of temperature on the conductance will depend on the 

 relative magnitude of the ionization and the viscosity effects; and, in 

 general, with increase in temperature the conductance of a solution may 

 either increase or decrease. At ordinary temperatures, the conductance 

 of many solutions increases with the temperature, and it was formerly 

 assumed that a positive temperature coefficient was a characteristic 

 property of electrolytic solutions. We now know, however, that this is 

 not the case and that the temperature coefficient of solutions may be 

 either positive or negative and that, in a given solvent, the temperature 

 coefficient is a function of the temperature as well as of concentration, 

 and that the sign of the temperature coefficient may change with tem- 

 perature as well as with concentration. 



Considering, first, the conductance as a function of temperature, the 

 concentration remaining fixed, it is found that, in general, the con- 

 ductance increases with the temperature at low temperatures; but as the 



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