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Department of Inorganic and Analytical Chemistry, School of Chemistry, Andhra University, Visakhapatnam-530 003, Andhra Pradesh, India E-mail : gollapallinr@yahoo.com Manuscript received online 12 October 2012, accepted 01November 2012 The protonation constants of 2,3-dihydroxybenzoic acid and malonic acid at 303.0 ± 0.1 K and 0.16 mol dm-3 ionic strength in 0-60% v/v dioxan-water mixtures were determined by the pH-metric method using MINIQUAD75 computer program. Selection of the best fit chemical model of the protonation equilibria is based on standard deviation in protonation constants and residual analysis using crystallographic R-factor and sum of squares of residuals in all mass balance equations. Linear variation of protonation constants with inverse of dielectric constants of the solvent mixture has been attributed to the dominance of the electrostatic forces. Distributions of species, protonation equilibria and effect of influential parameters on the protonation constants have also been discussed. |
