In this study, water activities for the ternary system of {L-serine + 1-carboxymethyl-3-methylimidazolium chloride [Cmmim][Cl] + H2O} and their corresponding binary aqueous solutions have been measured using an improved isopiestic method over the entire homogeneous mixing range at 298.15 K. For the same system, the solubility of the L-serine at various IL concentrations was measured at 298.15 K using gravimetric method. From the vapor-liquid equilibrium measurements, values of the vapor pressure, osmotic coefficient and activity coefficient of solutions were determined. The experimental data for the activity of water, collected in this work, were accurately correlated with segment-based local composition models of the NRTL, modified NRTL, Wilson and NRF-NRTL. The results showed that these models can accurately correlate the water activity data generated in this work. Also the above local composition models used to describe the solubility of amino acid in pure water and in aqueous IL solutions. (C) 2013 Elsevier B.V. All rights reserved.