CONDUCTION PROCESS IN ELECTROLYTES 41 



not known whether the laws of dilute solutions are inapplicable or 

 whether some other discrepancy has arisen. 



In the case of salts of higher type, and even in that of the simpler 

 types of salts, there is always a possibility that the ionization process as 

 assumed in calculating the ionization from conductance measurements 

 does not correspond to the true reaction. For example, in calculating the 

 ionization of barium chloride, it is assumed that the reaction takes place 

 according to the equation: 



BaCl 2 = Ba" + 2CK 



It is possible, however, that ionization may take place in several stages, 

 an intermediate reaction of the type: 



BaCl 2 = BaCl + + Cl- 



intervening. If an intermediate reaction of this type takes place, then 

 it is obviously impossible to calculate the degree of ionization from con- 

 ductance measurements. So far, it has proved difficult to establish the 

 existence of intermediate ions. In general, it is to be expected that if 

 intermediate ions exist, the transference numbers will vary markedly 

 with the concentration. It should be noticed in this connection that 

 those electrolytes, which exhibit the greatest divergence between the 

 ionization values as calculated from conductance and from freezing point 

 data, also exhibit a marked change in their transference numbers with 

 change of concentration. In the case of sulphuric acid 28 the existence of 

 an intermediate ion has been definitely established; and various consid- 

 erations, based upon the solubility of salts in the presence of other salts, 

 lend support to the view that intermediate ions exist in solutions of 

 many salts of higher type. 29 



In any case, it is important to note that the values of i as deter- 

 mined from freezing point and from conductivity determinations appar- 

 ently approach the same limit at low concentrations, and, moreover, the 

 limits approached are in agreement with the constitution of the salts in 

 question. So, for example, in the case of the binary electrolytes, the 

 limit approached is 2, in that of ternary electrolytes 3, in that of quater- 

 nary salts 4, etc. No case has been observed in which the limit ap- 

 proached is greater than that corresponding to the constitution of the 

 salt. 



6. Applicability of the Law of Mass Action to Electrolytic Solutions. 

 On their surface, the results of conductance and of freezing point meas- 

 urements appear to be in substantial agreement with the fundamental 



M Noyes and Eastman, Carnegie Report No. 19, p. 241. 

 Harkins, J. Am. Chem. Soc. 5S f 1808 (1911). 



