Potentiometric pH measurements of 0.01 mol.kg(-1) aqueous solutions of hexanoic, heptanoic, and benzoic acids in 0.1 mol.kg(-1) NaCl media were performed using a flow-through electrochemical cell with two pressure-balanced hydrogen platinum electrodes. The dissociation constants of these carboxylic acids were determined on the basis of pH values measured at temperatures from (322 to 673) K and pressures of (23 and 30) MPa. The dissociation constants were consistent with the literature values determined from calorimetry, electrical conductivity, and potentiometry at temperatures up to 523 K. A simple Born model for describing temperature and pressure dependence of the dissociation constants was used to correlate the data.