Abstract In this work, we have measured the new density and sound velocity data of amino acid L-serine in aqueous solutions of ammonium di-hydrogen citrate at different temperatures. Furtheremore, the improved isopiestic method is used to obtain activities of water for the aqueous solutions of L-serine+ammonium dihydrogen citrate at 298.15 K and a thermodynamic model is used for the correlation of the experimental water activity data. The apparent molar volumes and apparent molar isentropic compressibility of alanine at different investigated solutions have been calculated from the density and sound velocity experimental data.
