196 



WORK OF P. B. DAVIS. 



100 



3 



-e 

 c 

 c 



o 

 C 



'S 



a. 



than that of the solvent. Even at 75, rubidium chloride, which increases the fluidity 

 the least, shows a positive fluidity coefficient of 0.3 per cent for the N/10 solution. 



A table of per cent temperature coefficients of fluidity is given with each table of 

 viscosities. These are seen to be almost equal to the temperature coefficients of 

 conductivity, but in every case are somewhat larger. This is to be accounted for 

 by the decrease in association of the solvent with rise in temperature, causing a 

 decrease in the ionization of the solute and therefore a smaller conductivity. This 

 would in part offset the increase in conductivity due to an increase in the velocity 

 of the ions, because of the decrease in the viscosity of the 

 solvent with rise in temperature. 



The greatest viscosity lowering or increase in fluidity is 

 to be observed in the case of the normal solution. This 

 is obvious, since the effect is proportional to the concen- 

 tration. The dilution curve does not pass through a 

 minimum, but becomes asymptotic to that of the solvent 

 at dilutions beyond the N/50. The percentage increase 

 in fluidity becomes less also with rise in temperature, 

 which may be accounted for by the change in the molec- 

 ular aggregates of the sol- 

 vent and by the greater 

 effect of temperature than 

 of the dissolved salt on the 

 viscosity of the solvent. 



With the above facts in 

 view, it is possible to ex- 

 plain the minima found at 

 low temperatures in the 

 conductivity curves for the 

 concentrated solutions. 

 These minima are more 

 marked at 25, and in the 

 case of those salts which 

 give the greatest lowering 

 of the viscosity of glycerol, viz, ammonium and rubidium iodides. In the concen- 

 trated solution (N-N/4) the ionization is nearly constant, while the negative vis- 

 cosity effect decreases with increased dilution. 



Reference to fig. 84 will show that the conductivity and fluidity curves at 25 

 for rubidium iodide are practically parallel up to and through the N/10 solution. 

 Beyond that dilution the increased ionization causes a rise in the conductivity curve, 

 while the fluidity curve becomes the asymptote of the solvent. Here we have con- 

 ductivity varying directly as the fluidity or inversely as the viscosity. It is of 

 interest to observe that a salt can lower the viscosity of a solvent to such an extent 

 as to increase its own conductivity in that solvent. Fig. 85 shows similar results with 

 ammonium iodide. 



Table 142 shows the relative percentage increase in fluidity produced by normal 



72 

 '3 



I 



Per cent. Glycerol 



Fig. 83. Specific Conductivity and Fluidity of Glycerol- 

 Water Mixtures at 25. 



