300 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



If the electromotive forces have been determined experimentally, they 

 may be expressed as a function of the total salt concentration C g by 



means of this equation. In this case, the function /, &i includes not only 



the change in the potential of the electrolyte due to the internal forces 

 of the system, but it also includes a term which takes into account the 

 change in the expression due to the substitution of G S for C + and C~. 



The electromotive force of concentration cells for a great many elec- 

 trolytes has been measured by various investigators. 25 Only a few 

 examples of the results obtained will be given here to show, in a general 

 way, the manner in which the potential of an electrolyte varies with the 

 concentration. In Table CXXIV are given values of the electromotive 

 force of concentration cells with hydrochloric acid as electrolyte between 

 silver chloride electrodes. 26 The concentration of the concentrated solu- 

 tion is in this case throughout 0.1 N. The concentration of the dilute 

 solution is given in the first column, in the second column is given the 

 value of the electromotive force as measured, in the third and fourth 



C C 

 columns are given the values ~ and -~, as determined from conduc- 



S 2 C ^2 



tance measurements, and in the fifth and sixth columns the values of the 

 same ratios as calculated from Equations 93 and 96, assuming ,7 = 0. 



TABLE CXXIV. 



c i c u 



COMPARISON OF VALUES OF - AND FOE HC1 AS DERIVED FROM 



L iz C ^2 



CONDUCTANCE AND ELECTROMOTIVE FORCE MEASUREMENTS. 



(Cal.) (Cal.) 



C ii C Ui C i! C u 1 



Concentration ^ -^- ^ 



of dilute sol. E.M.F. L i 2 ^uz L i* L u z 



0.02 0.07617 4.78 7.76 4.57 20.9 



0.01 0.10913 9.49 17.3 8.82 77.7 



0.002 0.18711 46.7 112.5 41.8 1744.0 



c i 



It will be observed that the calculated values of the ratio ~ do not 



C iz 

 differ greatly from those derived from conductance measurements, but 



"Linhart, J. Am. Chem. Soc. 39, 2601 (1917) ; ibid., Ifl, 1175 (1919) ; Ellis, ibid., 

 S8, 737 (1916) ; Noyes and Ellis, ibid., 39, 2532 (1917) ; Lewis, Brighton and Sebastian, 

 ibid., 39, 2245 (1917) ; Allmand and Polack, J. Chem. Soc. 115, 1020 (1919) ; Randall 

 and Cushman, J. Am. Chem. Soc. 40, 393 (1918) ; Harned, ibid., 37, 2460 (1915) ; 

 Loomis, Essex and Meacham, ibid., 39, 1133 (1917) ; Loomis and Acree, Am. Chem. J. 46. 

 632 (1911) ; Maclnnes and Beattie, J. Am. Chem. Soc. 42, 1117 (1920). 



Tolman and Ferguson, J. Am. Chem. Soc. 34, 232 (1912). 



