Determination of carboxylic acid dissociation constants to 350°C at 23 MPa by potentiometric pH measurements

The dissociation constants of aqueous ethanoic, propanoic, butanoic, pentanoic, and hexanoic acids were determined in 0.1 mol·kg^-1 NaCl media at temperatures from (19.4 to 350.4)°C and 23 MPa by a flow-through electrochemical cell with a pressure-balanced hydrogen platinum electrode. Temperature dependence of K values shown by each acid were qualitatively similar. The values are consistent with the literature values determined from potentiometry, calorimetry, and electrical conductivity. An empirical density model for the description of the temperature dependence of the equilibrium constants was used to correlate the data.