308 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



acid in water at 18 varies from 0.168 at 0.005 N to 0.165 at 0.1 N. 40 

 In a sense, this does not appear to be a great change in the value of the 

 transference number. Nevertheless, it is in excess of what might be 

 expected from the viscosity effect in these solutions. Furthermore, the 

 conductance of the chloride ion as calculated from the transference 

 number and the degree of ionization does not correspond with the value 

 of the conductance of the chloride ion at infinite dilution in solutions of 

 potassium chloride. Assuming for the transference number of the 

 chloride ion in hydrochloric acid the value 0.167 and for the ionization 

 the value 0.972 and for the conductance the value 369.3 at 0.01 N and 

 18, we obtain, for the conductance of the chloride ion, the value 



x 167 



Q7Q = 62.68. At infinite dilution the con- 



ductance of the chloride ion has a value of 65.5. It appears, then, 

 that up to a concentration of 0.01 N the conductance of the chloride ion 

 has fallen from a value of 65.5 to a value of 62.68. This value is obvi- 

 ously subject to a correction, since, in calculating the -value of y by the 



ratio r-, it has been tacitly assumed that the speed of the ions remains 

 A 



constant. 



Noyes 41 called attention to this discrepancy which exists in the case 

 of the strong acids. Lewis 42 showed that the ionization of different 

 chlorides as calculated from the conductance of the chloride ion at a 

 given concentration is the same for all chlorides. Maclnnes 43 has inves- 

 tigated the conductance of various ions at higher concentrations in some 

 detail. The conductance of an ion at a given concentration is obtained 

 by multiplying the conductance of the electrolyte by the transference 

 number of the ion in question at that concentration. In the case of the 

 chlorides, he obtained the following results: 



XLIII will show that the conductance of lithium, caesium and potassium chlorides Is 

 affected to almost the same extent on the addition of raffinose. Evidently, the viscosity 

 change due to raffinose affects the L.i+, Cs+ and K+ ions to the same extent. From the 

 game table, it is evident that the conductance of potassium chloride and lithium chloride 

 is altered to very nearly the same extent, even on the addition of some non-electrolyte of 

 relatively low molecular weight. In methyl alcohol, however, the exponent p is markedly 

 larger for LiCl than for CsCl. In the presence of this non-electrolyte, the influence of 

 viscosity on ion conductance depends upon the nature of the ion. Correspondingly, Mil- 

 lard (loc. cit.) found that the transference number of the lithium ion in lithium chloride 

 solution is decreased from 0.322 to 0.307 on the addition of 0.4 mol of methyl alcohol 

 per 1000 g. of water. The viscosity effect due to the electrolyte itself has an influence 

 on the conductance of an ion which differs markedly from that due to a non-electrolyte 

 of large molecular weight. In considering the influence of viscosity on the speed of an 

 ion, the nature of the particles to which the viscosity change is due must not be lost 

 sight of. 



Noyes and Kato, J. Am. Chem. Soc. 30, 318 (1908). 



"Noyes and Sammet, J. Am. Chem. Soc. 24, 944 (1902) ; ibid.. 25. 165 (1903) : Ztschr 

 f. phya. Cfhem. 43, 49 (1903) ; Noyes and Kato, ibid., 62, 420 (1908). 



"Lewis, J. Am. Chem. Soc. 3J f , 1631 (1912). 



"Maclnnes, J. Am. Chem. Soc. 41, 1086 (1919) ; ibid., 43 f 1217 (1921). 



