Ionic Sizes in relation to the Conductivity of Elect roli/lex. f>(j:> 



" Tonic Sizes in Relation to the Conductivity of Electrolytes." 

 By W. R. BOUSFIELD, M.A., K.C., M.P. Communicated by 

 Professor LARMOTI, Sec. R.S. Received February 10, Read 

 March 9, 1905. 



(Abstract.) 



The law of mass action, which gives us Ostwald's law for weak 

 electrolytes, has not hitherto been harmonized with the empirical data 

 for strong electrolytes. But it may be reconciled with the conductivity 

 data for strong electrolytes as well as weak, on the hypothesis that the 

 ions of an electrolyte consist of molecular aggregates in combination 

 with water, and on this hypothesis gives Van't Hoff's Law. 



If Stokes's results as to the motion of a sphere in a viscous fluid be 

 -applied to the motion of the ions of a binary electrolyte, it is again 

 necessary, in order to reconcile theory with empirical facts, to make the 

 same assumption, and to suppose that the ions are molecular aggregates 

 largely composed of water molecules, the size of an ion depending 

 upon the amount of water in combination with it, and being a function 

 of the temperature and concentration. 



Upon this hypothesis the form of the function may be represented, 

 within a temperature range of to 36 C., and a concentration range 

 <(in the case of KC1) from twice decinormal to infinity as 



rjr = (I + AT + BT 2 ) (1 +CA~) 



where h is the " hydration," i.e., the ratio of the molecules of water- 

 present to the molecules of the solvent, A and B are the radial 

 temperature coefficients, C the radial concentration coefficient, and T is 

 temperature - 18. 



A correction for the coefficient of ionization is thus attained, which 

 gives the true coefficient of ionization in the case of KC1 as 



A 1 1 



where / is the fluidity of the solution. 



With this coefficient of ionization Van't HofFs law, modified by 

 substituting the "hydration" of the solute for its concentration, gives 

 an accurate -agreement with experimental results to within an error of 

 1 part in 2000 down to twice decinormal solutions a greater accuracy 

 than has been attained by the best empirical formula hitherto 



proposed. 



The water entering into combination with the ion is probably 

 abstracted from the solvent largely as "trihydrol" or "hydrol," according 

 to the temperature of the solution, and enters into combination with the 

 ion as " dihydrol," thus causing contraction. 



