116 Studies on Solution. 



conductance of aqueous solutions, presented a possible means of deter 

 mining A in alcoholic solutions. This function has the form 



where A is the equivalent conductance at the concentration c (1/F) . K 

 is a constant, and n is a number which, for aqueous solutions, lies 

 between 1.3 and 1.7. The value of n is so chosen that the graph 

 obtained by plotting the reciprocal of the equivalent conductance 

 (I/A) at the various concentrations (c) against (cA) 71 "" 1 is nearly a 

 straight line. Two other graphs corresponding to neighboring values 

 of n, on opposite sides of the first line, are also drawn so as to aid in 

 determining the most probable point at which the graphs cut the 

 I/A axis. 1 This point is 1/A , the reciprocal of the limiting conduc- 

 tivity. 



This procedure was followed, using the data at 25 of sodium tri- 

 chloroacetate, salicylate, orthonitrobenzoate, 2, 4 dinitrobenzoate, 

 and picrate. The graphs obtained are in every respect similar to those 

 for aqueous solutions, except that the value of n lies between 1.7 and 

 1.8. The values of Ao obtained for the above salts at 25 are: 



Sodium trichloroacetate ......................... 41.6 



Sodium salicylate ................................ 39 . 9 



Sodium orthonitrobenzoate ....................... 38 . 



Sodium 2, 4 dinitrobenzoate ...................... 39 . 2 



Sodium picrate .................................. 44 . 7 



From these figures the percentage dissociation of these salts is obtained 



by means of the familiar formula a = -r-- 



AO 



While the procedure outlined above is thus proved to give satisfactory 

 results in alcoholic solutions, the calculations are quite laborious, and 

 advantage is taken of a much shorter method of approximating A , 

 suggested by Randall. 2 It is a fact that as the zero of concentration 

 (infinite dilution) is approached, the difference in the percentage 

 ionization of all salts approaches zero. 



Randall makes the provisional assumption that the ionization of 

 salts of the same type (such as thallous chloride and potassium chloride) 

 is the same. Knowing the percentage dissociation of potassium 

 chloride at various dilutions very accurately, he calculates the value of 

 A for thallous chloride by means of the equation 



A =A/a' 



in which a' is the percentage dissociation of KC1 at any given dilution 

 and A is the molecular conductance of T1C1 at the same dilution. 

 Such a calculation gives values for A which approach a constant figure 

 with increasing dilution. 



See J. Johnston: Journ. Amer. Chem. Soc. 31, 1010 (1909). 

 2 Journ. Amor. Chem. Soc. 38, 788 (1916). 



