Apparent molar volumes, V-2,V-phi, Of L-aspartic acid and L-glutamic acid have been determined in aqueous solutions of (0.1, 0.25, 0.5, and 1.0) mol . kg(-1) of lithium acetate dihydrate, magnesium acetate tetrahydrate, and calcium acetate at T = (288.15, 298.15, 308.15, and 318.15) K by density measurements. The data have been used to calculate partial molar volume, V-2 degrees, and transfer function, Delta V-t degrees, at infinite dilution from water to aqueous solutions of co-solutes by applying the correction due to ionisation of amino acids. Partial molar expansibilities, V degrees(E), hydration numbers, n(H), and interaction coefficients of amino acids have also been determined. The dependence of above thermodynamic functions on concentration, temperature and nature of co-solute has been discussed in terms of various interactions taking place between hydrophobic and hydrophilic parts of amino acids and ions of co-solutes. Further, a comparison between present work and data reported in the literature for neutral amino acids DL-alanine, DL-alpha-amino-n-butyric acid and their corresponding hydroxy derivatives, L-serine and L-threonine in aqueous solutions of these co-solutes has been made. (C) 2008 Elsevier Ltd. All rights reserved.