The solubility of benzoic acid and 2-hydroxybenzoic acid (salicylic acid) in water was determined at temperatures ranging from (298 to 473) K under a constant pressure of 5 MPa. The mole fraction solubility of these acids was enhanced by about two orders of magnitude when the water temperature was raised from (298 to 423) K. A new approximation model was developed to predict the solubility of solid organic acids in subcritical water at elevated temperatures. Our new model gives a better prediction for the solubility of the two acids than the approximation models reported in the literature.