66 



CONDUCTIVITY AND VISCOSITY IX MIXED SOLVENTS. 



TABLE 43. Comparison of temperature coefficients of conductivity and fluidity for 



various electrolytes. Continued. 



DISCUSSION OF RESULTS. 



The value of the quotient 



Ac/. - 



is a measure of the parallelism 



between the two phenomena decrease in conductivity and decrease in 

 fluidity. If the decrease were the same in both cases, other conditions being 

 the same, the value of the quotient would be zero. The fact that it is not 

 zero indicates that the decrease in ionic mobility resulting from the decrease 

 in fluidity is not proportional to the latter. 



When we come to compare the effect in the case of potassium iodide in 

 mixtures of the two alcohols and water (tables 37 and 38), it is seen that the 

 effect of decrease of fluidity on ionic mobility is greatest in the ethyl alcohol 

 mixtures, or the two effects are here most nearly parallel. The effect is less 

 for potassium iodide in methyl alcohol mixtures at both temperatures of ob- 

 servation, and 25. It is to be remembered that we are leaving out of 

 account possible differences of dissociation. Increase in dissociation (in the 

 mixture) over that of the corresponding aqueous solution would diminish 

 the effect of decrease in fluidity. Apparently, this possible change in disso- 

 ciation can not be very great, as some of our measurements show. A far 

 greater and entirely impossible change in dissociation would be necessary to 

 account for the difference in the two effects. 



The minimum is much more pronounced in the methyl alcohol mixtures. 

 It occurs, however, in the ethyl alcohol mixtures generally at 0, but is not 

 very marked. We have just seen that the real effect is greater in the latter 

 case, when we make a proper comparison. The reason why it is not so evi- 

 dent in the case of the ethyl alcohol mixtures is to be found in the small con- 

 ductivities in ethyl alcohol; these, in turn, as will be shown in the last part of 

 this section, being small, on account of the relatively great viscosity of 

 ethyl alcohol and its rather small dissociating power. On the other hand, 



