146 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



evident from Figure 32. As a rule the maximum lies in the neighborhood 

 of 25 C but the temperature of the maximum is a function of concen- 

 tration and with increasing concentration the maximum is displaced 

 toward lower temperatures. The curves for different electrolytes are 

 similar, indicating that the underlying phenomenon is the same in all 

 cases. As the critical temperature is approached, the conductance ap- 

 proaches a very low value, and it appears as though the curve would cut 

 the axis of temperatures at a point near the critical temperature. The 

 conductance, however, does not, in fact, fall to zero at the critical point, 

 but has appreciable values at temperatures much above that point. The 

 phenomenon in the neighborhood of the critical point will be discussed 

 in detail in another section and need not be further considered here. It 

 may be stated, however, that the property of forming conducting solu- 

 tions with electrolytes is not peculiar to the liquid state but is one com- 

 mon to fluid systems. 



The .form of the conductance-temperature curve is the same in all sol- 

 vents. The conductance of a considerable number of solutions in sul- 

 phur dioxide has been measured 3 at higher temperatures and the curves 

 obtained have a form which corresponds with those of ammonia solu- 

 tions. In solutions of KI in methylamine the form of the curve differs 

 slightly in that, at very high temperatures, the conductance appears to 

 approach the axis of temperatures asymptotically. In the alcohols, 4 

 as well as in water, 5 the conductance-temperature curves are of the same 

 general type. 



2. Conductance of Aqueous Solutions at Higher Temperatures. 

 In order to proceed with the discussion of this subject, it is necessary to 

 have some notion as to the degree of ionization of the electrolyte in solu- 

 tion. The degree of ionization of non-aqueous solutions at higher tem- 

 peratures is unknown. In other words, we do not have a sufficient num- 

 ber of measurements at a series of temperatures and concentrations to 

 enable us to determine the value of A at these temperatures. For 

 aqueous solutions, however, a large amount of material is available, 

 having been obtained by A. A. Noyes and his associates, 6 and from these 

 data the effect of temperature on the ionization of salts becomes ap- 

 parent. 



In the following table are given values of the equivalent conductance 

 for potassium chloride at a series of temperatures and at the concentra- 

 tions 0.08 and 0.002 normal. 



1 Walden and Centnerszwer, ZtscTir. }. phys. Chem. 39, 542 (1902) 

 Kraus, Phy8. Rev. 18, 40 and 89 (1904). 

 8 Noyes, Carnegie Publication, No. 63, pp. 47, 103, and 266. 

 Noyes, loc. cit. 



