POLYELECTROLYTE TITRATIONS - THE SYSTEM NA+-H+ ON CARBOXYMETHYLDEXTRAN

From acid-base titrations of carboxymethyldextran (HP) the equilibrium "constant" for the reaction H+ (aq) + P− rlhar2; HP (K) has been computed. This quantity varies with the degree of dissociation, α, indicating nonideal behavior. The data have been fitted to a three-parameter model, which takes nonideality into account. The model gives a satisfactory fit to data pH(v). Moreover, the three-parameter model offers an estimate of the intrinsic protonation constant, giving log Kint = 3.39 ∓ 0.03. The data also permit an estimate of the equilibrium constant for the reaction [Formula Present] i.e., the free energy of proton transfer at infinite dilution from the aqueous phase to the polyelectrolyte at infinite solution giving 394;G = -4.67 kJ. © 1993 by Academic Press, Inc.