Organic acids in hydrothermal solutions: standard molal thermodynamic properties of carboxylic acids and estimates of dissociation constants at high temperatures and pressures.

Experimental standard partial molal volumes, heat capacities, and entropies as well as apparent standard partial molal enthalpies and Gibbs free energies of mono- and dicarboxylic acids and their anions at low temperatures and pressures are used to generate correlations for predicting the same properties at high temperatures and pressures for 59 carboxylic and 18 hydroxyacid species with the revised Helgeson-Kirkham-Flowers (HKF) equation of state. Predicted equilibrium dissociation constants are compared with experimental values from the literature and tabulated as functions of pressure and temperature for 25 carboxylic acids and nine hydroxyacids. Close agreement between independent predictions and experimental data supports the generality of the computational techniques and the accuracy of predicted data. These results allow incorporation of a wide variety of organic acids into quantitative interpretations of geochemical processes.