24 Mr. W. Sutherland on Ionization in Solutions 



chemical equilibrium will determine the amounts o£ the 

 two types of ionization occurring, and although the ionization 

 of the H 2 S0 4 is complete, the formula for the conductivity of 

 its solutions may be exceptional through the necessity for 

 expressing the varying chemical equilibrium. To this class 

 of exceptions I thought there belonged the interesting case 

 of acid compounds of globulin experimentally investigated 

 by Hardy and discussed by me (Proc. Roy. Soc. 6th Dec. 

 1906). But the theory of the present paper leads to a 

 simpler and more thorough comprehension of it. This case 

 and the whole theory of dilute solutions can be simplified by 

 looking at our formulae in a different way. Let us write (23) 

 in the following form, which includes the result just proved 

 that v\y 2 becomes v 1 v 2 (y l + v 2 ) 2 : 



l/\= l/(Aoi + A 02 )+iv 1 v 2 (r 1 + v 2 ) 2 (v lW )V(Aoi + A 02 ). (24) 



Here 1/(A 01 + A 02 ) is proportional to the time taken by the 

 two opposite ions to approach one another through a centi- 

 metre with their relative velocity at infinite dilution or 

 zero concentration ; while the second term on the right 

 is proportional to the increase of this time caused at con- 

 centration n by the viscosity due to the electric forces acting 

 between the ions. Thus we have a simple means of thinking 

 about the effects of extraneous causes on electrolytic con- 

 duction, by considering them as causing variations in this 

 time taken by the two ions to approach one another through 

 a centimetre. In the case of* globulin dissolved in the 

 minimum of HC1 and investigated as to conductivity at 

 different concentrations, it appears that at zero concen- 

 tration the molecular conductivity is that of HCi com- 

 pletely ionized. But at finite concentrations the molecular 

 conductivity is less than that of HCI at the same dilution. 

 Here, then, we might have a case of a solute which 

 could ionize in two different ways, one yielding H and 

 01 ions and neutral globulin, the other yielding com- 

 plex ions in which H and CI are attached to globulin. 

 Although in such a case the ionization might be complete, 

 yet, as the H and CI travel much more slowly when they 

 form parts of the complex ions than when they exist as 

 separate ions, we get an effect equivalent to incomplete 

 ionization. We could speak also of the degree of dissociation 

 of the compound of globulin and HCI, meaning thereby the 

 fraction of a second which each CI and H atom spends as a 

 free ion apart from globulin. But the conductivity depends 

 on this degree of dissociation. Hence in such cases we have 

 conductivity a function of dissociation, although at any 



