ERRORS ENCOUNTERED IN THE DETERMINATION OF PITZER PARAMETERS FROM STOICHIOMETRIC EQUILIBRIUM-CONSTANTS

According to Pitzer's formalism, the pK (stoichiometric equilibrium c onstant) of a monoprotonation equilibrium can be related to the ionic strength I of the medium through the equation pK = A + BI + Cf(2)(I) + DI2. Taking into account that commercially available glass H+ electr odes are widely used for the determination of acid-base equilibrium co nstants we believed it of intereset to analyse by simulation the behav iour of this equation towards certain types of error, viz, random erro rs in pK, the number of points used to construct the pK* vs I plot an d the fitting range used, systematic errors in I and the effect of mul ticollinearity. The results thus obtained are compared with those prov ided by other commonly used potentiometric methods for the determinati on of Pitzer's ionic interaction parameters and can be used by researc hers as guidelines for typical errors made in applying Pitzer's formal ism to pK (pH-metrically measured) vs I data.