6 INTRODUCTION. 



There yet remain for consideration the several maxima of conductivity noticed 

 in this work as well as in that of Bingham. The discussion of the latter work has 

 shown that it is improbable that the maxima are due to an increase in dissociating 

 power in the mixture where they occur. Moreover, an examination of the con- 

 ductivities of lithium bromide and cobalt chloride shows that complete dissociation 

 is more nearly reached in the pure solvents than in the mixtures where the maxima 

 are found. Hence, it was concluded that the cause of the effect is primarily a change 

 in the dimensions of the ionic spheres. 



Some points of interest were noted in connection with the temperature coefficients of 

 conductivity and of fluidity. First, in nearly every case the temperature coefficients 

 of conductivity are greater in the more dilute than in the more concentrated solutions. 

 The work of Jones has shown that in practically all solutions there is some combi- 

 nation between solvent and solute, and that the solvates become more complex as the 

 dilution increases. Therefore, change in temperature, which affects the complex sol- 

 vates most, has a greater effect on the conductivity of the more dilute solutions. 



A second point worth noting was that in certain solutions negative temperature 

 coefficients of conductivity were found. These manifested themselves in solutions 

 of cobalt chloride in acetone, in 75 per cent acetone and methyl alcohol, and in 50 

 and 75 per cent acetone and ethyl alcohol. In the 75 per cent acetone and methyl 

 alcohol, when V = 200, the temperature coefficient is zero. 



The change in conductivity with temperature is the algebraic sum of two oppos- 

 ing influences. First, rise in temperature diminishes dissociation; second, rise in 

 temperature is accompanied by an increase in fluidity. The first of the processes 

 tends to decrease conductivity, the second to increase it. When the sum is positive 

 we have increasing conductivity with rise in temperature, as is usually found to be 

 the case. In the one instance mentioned above the two forces are equal, and the 

 conductivity is independent of the temperature. 



The investigation of Jones and Veazey 1 included a study of the behavior of copper 

 chloride and potassium sulphocyanate. Both of these electrolytes gave results 

 which were almost entirely "normal;" that is, conductivity curves followed fluidity 

 curves in every case except two. These exceptions were the curves for copper 

 chloride in mixtures of the alcohols with water. No minima were found here cor- 

 responding to the well-marked minimum in fluidity, although the conductivities 

 were always less than required by the law of averages. An inflection-point occurs 

 between the 50 and 75 per cent mixtures. The conductivity curves of potassium 

 sulphocyanate show no such irregularity, but are in every respect parallel to the 

 fluidity curves of the solvents. 



In addition to determining the fluidities of the various solvent mixtures, Jones 

 and Veazey measured the fluidities of solutions of potassium sulphocyanate in these 

 mixtures. It was found that in many cases the fluidity of the solution is greater than 

 the fluidity of the solvent; in other words, potassium sulphocyanate, under certain 

 conditions, has a negative viscosity coefficient. In mixtures of methyl alcohol and 

 water the viscosity of the tenth-normal solutions is less than that of the 0, 25, and 

 50 per cent solvent mixtures and greater than the 75 per cent mixture, becoming 



'Araer. Chem. Joura., 37. 405 (1907); Zeit. phys. Chem., 61, 641 (1908). 



