Characterization of the thermodynamic properties of some benzenepolycarboxylic acids: Acid-base properties, weak complexes, total and neutral species solubility, solubility products in NaClaq, (CH3)4NClaq and Synthetic Sea Water (SSW)

Abstract

The acid-base properties and solubilities of 1,2,3-, 1,3,5-, 1,2,4-benzenetricarboxylic and 1,2,4,5-benzenetetracarboxylic acids at T = (298.15 ± 0.15) K in NaClaq, (CH3)4NClaq and in Synthetic Sea Water are reported. In synthetic sea water, the data were analyzed by means of the single salt approximation (BA). For each ligand, the total solubility (ST) was determined and only in some cases it was possible to calculate the neutral species solubility (S0) and the Setschenow coefficients, because the formation of sparingly soluble species formed with the cation of the supporting electrolytes was often observed. Different stoichiometry were proposed for the precipitates and their corresponding solubility products were calculated at the different experimental conditions. The dependence of the protonation constants and solubility products on ionic strength was analyzed by Debye-Hückel type equations. The formation constants of the complexes formed by the different deprotonated species of the ligands with the cation of the supporting electrolytes were also determined.