156 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



Y' = T~j~ry F r strong electrolytes D has a value in the neighborhood 



of 0.35. The ionization at this concentration is therefore 0.26 and the 

 concentration of the salt at this ion concentration is accordingly in the 

 neighborhood of 4.0 normal. If the constant D is independent of tem- 

 perature, then the ionization at this concentration will remain fixed and 

 consequently, with increasing temperature, the conductance of the solu- 

 tion will increase throughout, since the fluidity of the solution increases 

 with increasing temperature. At very high and at very low concentra- 

 tions, therefore, the conductance of all solutions should increase with 

 increasing temperature. At intermediate concentrations, the ionization 

 decreases as the dielectric constant decreases ; that is, as the temperature 

 increases. The decrease in the ionization in this region is largely deter- 

 mined by the decrease in the value of the constant K and increase in 

 the value of the exponent ra. For higher values of the dielectric con- 

 stant and for salts having a high value of the constant K and low value 

 of the constant D and a value of the exponent m less than 1, the change 

 of the constants m and K has relatively a small effect upon the value of 

 the ionization at intermediate concentrations. As a result, at low tem- 

 peratures, or rather, for values of the dielectric constant greater than 

 about 20, the ionization changes but little as the temperature increases 

 and such solutions exhibit a positive temperature coefficient over the 

 entire range of concentration. When, however, the dielectric constant 

 falls below a value in the neighborhood of 20, the exponent m increases 

 markedly and the constant K decreases largely with temperature. Con- 

 sequently, at intermediate concentrations, the decrease in the ionization 

 more than compensates for the increase in the conductance due to the 

 increased fluidity of the solutions. The conductance of solutions at such 

 intermediate concentrations, therefore, decreases with increasing tem- 

 perature. 



In order to illustrate the effect of temperature upon the conductance 

 of solutions, ionization and conductance curves have been calculated for 

 an electrolyte having the constants given in the following table: 



TABLE LVIL 



ASSUMED CONSTANTS OF EQUATION 11 TO ILLUSTRATE THE EFFECT OF 

 TEMPERATURE ON CONDUCTANCE. 



t A XX 10* m D 



+ 10 240 5.2 1.21 0.4 



10 200 8.5 1.14 0.4 



30 160 13.0 1.05 0.4 



50 120 20.0 0.95 0.4 



