THEORIES RELATING TO ELECTROLYTIC SOLUTIONS 339 



trivalent salts, assuming x = 3, the minimum is at 0.01 m. Bronsted's 

 equations therefore account for the solubility relations of various salts 

 in a general way, including the minima which have been observed in the 

 case of salts of higher type. Adjusting the value of the constant x to 

 represent the experimental values in the best possible manner, Bronsted 

 has shown that his equations account for the observed solubilities up to 

 0.1 N, practically within the limits of experimental error. 



According to Bronsted's equation, the activity of all salts ultimately 

 passes through a maximum. Under these conditions, the solutions will 

 be unstable at the maximum point and the system in these regions should 

 separate into two liquid phases. In the case of salts of higher type, the 

 concentration at which this phenomenon should occur lies in regions 

 where the concentration is fairly low. Bronsted has actually been able 

 to observe separation of a liquid phase in solutions of salts of certain 

 trivalent ions. 



The results obtained, on comparing the thermodynamic potential of 

 electrolytes in aqueous solution, show that these values as derived by 

 different methods are in excellent agreement. Thermodynamic principles 

 alone are not capable of supplying information as to the nature or number 

 of the molecular species present in electrolytic solutions. The results are 

 naturally in agreement with the assumption that electrolytes are com- 

 pletely ionized and, in view of the fact that in the thermodynamic treat- 

 ment we are restricted to total concentrations and not to actual concen- 

 trations, the results are most simply interpreted on the basis of this 

 hypothesis. This, however, does not preclude the possibility that un- 

 ionized molecules or intermediate ions may exist, or, indeed, that other 

 complexes may be present in these solutions. 



3. Theories Taking into Account the Interionic Forces, a. Theory 

 of Malmstrom and Kjellin. A great many investigators have attempted 

 to account for the properties of solutions of electrolytes by taking into 

 account the forces acting between the charges. According to this view, 

 as was pointed out by Thomson 17 and by Nernst, 17a the ionization of an 

 electrolyte under given conditions should be the greater the greater the 

 dielectric constant of the medium. 



Among those who have attempted a solution of the problem by this 

 method are Kjellin 18 and Malmstrom. 19 These theories, which are prac- 

 tically the same, lead to an equation of the form: 



A log C { = log + log C u + 



"Thomson, Phil. Mag. [5], S6 t 320 (1893). 

 "Nernst, Ztschr. j. pliya. Chem. 13, 531 (1804). 

 "Kjellin, Ztschr. f. phys. Chem. 77, 192 (1911). 



18 Malmstrom, see Kjellin, above. 



