EQUILIBRIUM DISTANCE d^ FROM ^l j 



273 



occur when the ions approach within a distance of three water layers, and 

 that this interaction energy could not be described adequately by a cou- 

 lombic formulation, whether one used a macroscopic dielectric constant 

 or one that decreases with approach of the ions. The problem of hydra- 

 tion water displacement in ion-ion interactions is certainly not solved at 

 the present time. 



Fig. 6-16. Dependence of the interaction energy on the equiUb- 

 rium distance between — XH3+ and — C00~ groups (Eq. 6-109). 

 Curve A: r^ = 4 A; curve B: ry = 10.2 A; curve C: ionic atmos- 

 phere neglected. 



Many different approaches to the problem of the association of ions in 

 aqueous solution have been used and all of this work is intimately related 

 to the interactions between ionic groups on enzymes and inhibitors. Fuoss 

 (1958) has assumed the solvent to be a continuum and thus there are no 



