GENERAL SUMMARY AND CONCLUSIONS. 225 



the effect on conductivity of the increased velocity with which the ions move. 

 The result is a decrease in conductivity with rise in temperature. 



This explanation accounts entirely satisfactorily for the facts in the above 

 case. The alcohols and acetone are at ordinary temperatures highly asso- 

 ciated liquids. The effect of rise in temperature is to diminish their asso- 

 ciation and, consequently, their dissociating power. 



It is interesting to note in this connection that a solution was found that 

 had a zero temperature coefficient of conductivity. It was a solution of cobalt 

 chloride in a 75 per cent mixture of acetone with methyl alcohol, the solution 

 having a value of v = 200. 



The last investigation upon this problem that of Veazey has brought 

 out a number of points of interest. It consisted experimentally in measuring 

 the conductivities and viscosities of solutions of copper chloride and potassium 

 sulphocyanate in water, methyl alcohol, ethyl alcohol, and acetone, and in 

 binary mixtures of these solvents. 



The minimum in conductivity observed in the earlier investigations was 

 found for the above substances, and was shown to be a much more general 

 phenomenon than was supposed from any of the earlier work. It has been 

 pointed out that the minima in fluidity, or maxima in viscosity, correspond 

 to the minima in conductivity of the solutions of electrolytes in these solvents. 

 An explanation of why solutions of methyl alcohol or ethyl alcohol and water 

 are more viscous than either of the pure solvents alone was offered. 



These liquids are all highly associated. When one associated liquid is 

 mixed with another associated liquid, each diminishes the association of the 

 other. This means that the large molecules of each solvent are torn down 

 into a larger number of small molecules. This would increase the frictional 

 surfaces of the molecules that would be exposed to one another, just as small 

 shot would exert greater friction, in moving over one another in a manner 

 analogous to that followed by the molecules in producing viscosity, than 

 larger shot. The result of each associated liquid diminishing the association 

 of the other, would thus be to increase the viscosity of the mixture over that 

 of either pure solvent. 



This explains also why the conductivity curves for different dilutions of 

 the same substance generally approach one another as they approach the 

 minimum. Those mixtures of the solvents in which the conductivity minima 

 occur are the least associated, and, therefore, have the least dissociating 

 power. It is obvious that such mixtures would produce the least increase in 

 dissociation with increase in dilution, and, consequently, the conductivity 

 curves for the different dilutions would approach one another as they approach 

 the minima. Fact and theory are here in perfect accord. 



The minima in conductivity observed in the earlier work were also found in 

 a number of cases studied in this investigation. It was shown that this is 



