Crystallization Thermodynamics of m-Phthalic Acid in Water and Aqueous Acetic Acid Solutions

Using a laser observation technique, the saturation solubility and crystallization metastable zone width in water and aqueous acetic acid solutions of different acetic acid concentrations were determined. The solubilities of four systems were correlated by λh equation and the heats of crystallization were evaluated based on the equation. The calculated absolute average deviations(AAD) of the four systems were 5.78%, 2.02%, 3.74% and 1.56%, respectively. It was found that, the solubilities increased significantly with the increase of temperature in all reported systems, and that with the increase of acetic acid concentration in aqueous acetic acid solution as well,while the metastable width decreased with the increase of temperature and the presence of acetic acid. The enthalpy of mixing increased with the increase of temperature and solute concentration.