Density (rho) and red of sound (u) values have been measured of L-leucine + 0.5 mol.L-1 aqueous K2SO4/KNO3 and L-isoleucine + 0.5 mol.L-1 aqueous K2SO4/KNO3 systems for several molal concentrations of L-leucine/L-isoleucine at different temperatures T = (298.15, 303.15, 308.15, 313.15, 318.15, and 323.15) K. Using the experimental values of rho and u, the apparent molar volumes, partial molar volumes, transfer partial molar volumes, isentropic compressibilities, apparent molar isentropic compressibilities, partial molar isentropic compressibilities, and transfer partial molar isentropic compressibilities have been calculated. The measured and calculated thermodynamic parameters have been discussed in terms of zwitterion-ion, zwitterion-water dipole, ion-ion, and ion-water dipole interactions.