ELECTROLYTES IN MIXED SOLVENTS 197 



Extensive data are available which show that the examples given 

 above are typical of the behavior of solutions of electrolytes in mixed 

 solvents. The data do not have sufficient precision to make it possible 

 to determine the values of AO in the mixtures, fof which reason it is 

 necessary to consider only the general outline of the conductance curves. 

 It is evident that, in the case of solutions of salts which are highly ionized, 

 the conductance curves parallel the fluidity curves. If, however, the 

 electrolyte is only slightly ionized in one of the solvents, the addition of 

 the second component may cause a large shift in the conductance values 

 due, primarily, to a large change in the ionization of the electrolyte. It 

 should be noted that, whenever the fluidity of the solvent medium 

 changes, whether under the action of pressure or temperature, or whether 

 through a change in the viscosity of the medium due to the presence of 

 the electrolyte itself or due to the presence of a non-electrolyte, the con- 

 ductance is affected by the viscosity change, and, while the conductance 

 may not change in direct proportion to the fluidity change of the medium, 

 nevertheless the effect of fluidity change is very marked. These facts are 

 in entire accord with our notions as to the nature of the conduction 

 process. On the other hand, it is clearly evident that the conductance is 

 likewise dependent upon some other factor, namely the ionization. The 

 ionization is a function, in the first place, of the dielectric constant of 

 the solvent medium, as well as of the concentration of the electrolyte. 

 In the second place, however, the ionization is greatly affected by inter- 

 action between the dissolved electrolyte and the solvent medium. Ap- 

 parently, complexes are formed between the dissolved electrolyte and the 

 solvent, which are largely ionized. Certain solvents, such as acetone, 

 for example, appear to have a very small tendency to form complexes. 

 When salts, which exhibit a marked tendency to form complexes, are 

 dissolved in solvents of this type, the resulting ionization . is relatively 

 low. This effect is marked in the case of salts of the alkali metals. 

 Salts of sodium, potassium, rubidium and caesium are very largely 

 ionized in all solvents, apparently without exception, whereas the salts of 

 lithium exhibit a markedly lower ionization in many solvents, as for 

 example in acetone. As is well known, lithium salts exhibit a great 

 affinity for hydroxy-solvents, and apparently the formation of a complex 

 is a necessary condition for ionization in the case of salts of this type. 



In comparing the ionizing power of different solvents, therefore, it is 

 necessary to select such electrolytes as exhibit the least tendency to form 

 complexes. This has in general been done by various writers on this 

 subject. Nevertheless, it should be borne in mind that the possibility 

 always exists that a given electrolyte in a given solvent may exhibit 

 exceptional properties. 



