SOLUTIONS AS A FUNCTION OF TEMPERATURE 167 



ficiently low concentrations. It is to be borne in mind, however, that at 

 very high temperatures the value of the mass-action constant becomes 

 extremely low, as may be seen from the value of this constant in the case 

 of solvents having low dielectric constants. It is possible, therefore, 

 that, in the case of solvents having relatively low dielectric constants, the 

 mass-action constant has such a low value that a maximum in the con- 

 ductance curves will not be observed in dilute solutions. At higher con- 

 centrations, again, the maximum is displaced toward higher temperatures 

 and if it were possible to work with solutions of sufficiently high concen- 

 trations the maximum should disappear entirely. Data are not available 

 in this case at temperatures approaching the critical point, but, in solu- 

 tions in sulphur dioxide and ethyl amine, the conductivity increases with 

 the temperature over those ranges of temperature for which conductance 

 data exist. 



The conductance of a given solution, therefore, appears to be a func- 

 tion, primarily, of the fluidity of the medium and of its dielectric con- 

 stant. For a given type of salt the conductance curve in twp solvents at 

 different temperatures will be similar, provided that the two solvents 

 have the same value of the dielectric constant. 



4. The Conductance of Solutions in the Neighborhood of the Critical 

 PoinL Data relative to the ionization of solutions in the critical region 

 are entirely lacking, for which reason it is not possible to interpret the 

 results of conductance measurements with any degree of certainty. How- 

 ever, the conductance data indicate that the properties of solutions in 

 the critical region do not differ materially from those of solutions at lower 

 temperatures. Moreover, it appears that the property of forming elec- 

 trolytic solutions is by no means confined to the liquid state of matter. 

 Fluids above the critical point yield electrolytic solutions and even the 

 solvent vapors themselves, below the critical point, possess the power of 

 dissolving electrolytes, forming solutions which conduct the current. 



It has already been pointed out that, as the critical point is ap- 

 proached, the conductance of solutions in solvents of low dielectric con- 

 stant approaches a very low value, and that the conductance-temperature 

 curve if extrapolated would intersect the temperature axis at a tem- 

 perature not far removed from the critical temperature. It is known, 

 however, that, once the critical point has been reached, the conductance 

 falls only very slowly with increasing temperature. It other words, the 

 conductance-temperature curves exhibit a discontinuity in the immediate 

 neighborhood of the critical point. As will be seen below, this behavior 

 is what we should expect when conductance measurements are carried 

 out in sealed tubes, where the total volume of liquid and vapor remains 



