The thermodynamics of ionization of polycarboxylic acids

The influence of temperature on the adsorption of mellitic acid onto goethite

“…An increase in charge upon losing a proton will significantly increase the co-ordination of water molecules about the resultant mellitate ion, thereby decreasing the entropy of the system. The magnitudes of the entropy changes presented in this work are similar to those obtained previously [30]. Purdie and coworkers [30] also found similar small enthalpies to those found in this study for the reactions represented by the ionisation constants K a6 , K a5 and K a4 .…”

“…The magnitudes of the entropy changes presented in this work are similar to those obtained previously [30]. Purdie and coworkers [30] also found similar small enthalpies to those found in this study for the reactions represented by the ionisation constants K a6 , K a5 and K a4 . Small discrepancies can easily be accounted for by the differing experimental conditions, particularly the ionic strength and temperature range.…”

“…The acidity constants pK a6 and pK a5 determined at 25 • C are within about 0.5 units of the values found by Purdie et al [30] when those values are corrected to the ionic strength used in our experiments. The value of pK a4 found here is a little smaller (0.7 pH units), and doubtless includes contributions from other protonation reactions.…”

Effects of pH and organic solvent on chromatographic behavior in capillary electrochromatography

“…Since the dissociation constants for trimesic acid are pK, = 3.12, pK, = 4.10, and pK3 = 5.18 [13], trimesic acid dissociates completely in the eluent at pH 8.0. The elution order is reversed when the voltage is applied.…”

The Thermodynamic Overlapping pKa of the Antitumor Drug Ibrutinib Using Multiwavelength UV/VIS-Spectroscopy and Potentiometry

“…pK a values can be either experimentally measured or theoretically predicted: a. Many new substances are poorly soluble in aqueous solutions, conventional potentiometric determination of dissociation constants of these compounds can often be difficult [9]. Spectrophotometry is a convenient method to determine pK a in very diluted aqueous solutions (about 10 -5 to 10 -6 M), provided that the compound possesses pH-dependent light absorption due to the presence of a chromophore in proximity to the ionization centre [10][11][12].…”