216 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



Section XV). This even gives rise to a maximum value in the case of 

 the 0.1 normal solution of both salts at a temperature of about 280°. 

 "With more concentrated solutions this effect would undoubtedly be much 

 more pronounced, as is indicated by the dotted curve in Fig. 10. 



XV. Change of the Dissociation with the Concentration 



and Temperature. 



It has already been shown in Section XIII that the conductivity A 

 changes with the concentration C at all temperatures closely in accord- 

 ance with the equation A — A = K C*. Expressed in terms of the disso- 



A ,. _ 1 —x 



ciation, x = — j this becomes =- 



A C* 



K; that is, the fraction of the 



salt undissociated is directly proportional to the cube-root of the concen- 

 tration, or the concentration of the undissociated molecules, (1 — x) C, is 

 directly proportional to the f power of the total concentration. 



The change of the degree of dissociation with the temperature is 

 shown for both salts in Table XIII, and for sodium chloride in Fig. 12. 



TABLE XIII. 

 Dissociation. 



It will be seen that, especially in the 0.1 normal solution, the disso- 

 ciation has decreased very greatly at the higher temperatures, namely, 

 from 83-85 per cent at 18° to 60-61 per cent at 306° ; and that the 

 decrease is becoming extremely rapid at those temperatures, the course 

 of the curve indicating that the dissociation is very small iu the neighbor- 

 hood of the critical temperature (about 360°). 



