134 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 

 solutions of various electrolytes at a concentration of 0.01 N at a tem- 

 perature of 19.18, while in Figure 27 24 are shown values of -^ as cal- 

 culated from the measured values of g-, according to Equation 44. 



As stated above, the curve for sodium chloride corresponds with the 

 viscosity curve of pure water as determined by Cohen. It will be seen, 

 however, that the curves for other electrolytes differ from that of sodium 

 chloride and that, therefore, in these cases the pressure effect upon the 

 ions is not directly proportional to the viscosity change of the solution. 

 In the case of potassium chloride the conductance evidently increases 

 slightly more than corresponds to the viscosity change of the solution, 

 while for lithium chloride and hydrochloric acid the conductance increase 

 due to increasing pressure is enormously greater than the viscosity change 

 of the solution. On the other hand, in the case of potassium bromide, 

 sodium bromide, potassium iodide, and sodium iodide the conductance 

 change of the electrolytes is much smaller than the corresponding vis- 

 cosity change of the solution. Manifestly, the change in the speed of 

 the ions with pressure change is dependent not only on the viscosity of 

 the solvent medium, but also on other factors. What these factors are, 

 we do not know with certainty, but it appears probable that the speed 

 of the ions is affected by a change in their effective size. Such an effect 

 will obviously be a property of the ions themselves, which is in accord- 

 ance with Korber's observations. However we may interpret these 

 results, it is obvious that the speed of the ions in a dilute aqueous solution 

 is not determined primarily by the viscosity of the solution, although the 

 viscosity is an important factor. 



According to Equation 43, the value of the ratio -^L varies as a 

 function of concentration. In Figure 28 * 5 are shown values of the ratio 

 TT-^- for sodium chloride in water at 19.18 at a series of concentrations. 



At the highest concentrations the resistance of the solution increases 

 throughout with increasing pressure. This is in accord with Cohen's 

 observations on the viscosity of sodium chloride solutions, which, at 

 higher concentrations, exhibit a marked viscosity increase. As the con- 

 centration of the solution decreases, the curves exhibit a minimum. 

 Initially, with increase in pressure, the resistance of the solution decreases, 



* Korber, loc. cit. f p. 227. 

 Ibid., loo. cit., p. 234. 



