Solubility and Thermodynamic Behavior of Syringic Acid in Eight Pure and Water + Methanol Mixed Solvents

Abstract

In this work, the solubility data of syringic acid (SA) in eight mono solvents, including methanol, ethanol, 2-propanol, 1-butanol, 2-butanol, 1-hexanol, ethylene glycol, and ethyl acetate, and water + methanol mixtures were obtained experimentally in temperatures ranging from 283.15 to 323.15 K at 5 K intervals with a gravimetric method under a pressure of 0.1 MPa. It is found that the solubility of SA increases with increasing temperature in all selected pure and binary mixed solvents within the temperature range studied. The mole fraction solubility of SA is found to be highest in methanol and lowest in ethyl acetate. Additionally, three commonly used thermodynamic models, namely, the van’t Hoff equation, the modified Apelblat, and λh models, were applied to correlate the experimental solubility data. It is found that the three empirical thermodynamic models can satisfactorily correlate the solubility of SA in the solvents under investigated temperatures. The excess enthalpy of the solutions was predic...