Acid-base equilibria of phthalic acid in saline media: ion association from Pitzer equations.

The protonation constants of 1,2-benzenedicarboxylic acid (phthalic acid) at 25 degrees C in NaCl and CaCl(2) (ionic strengths ranging from 0.1 to 2 mol kg(-1)) were determined potentiometrically, and the results were analyzed by means of Pitzer equations. The values of the logarithm of the first and second dissociation constants ranged from 2.