The present work studies the characterization of binary and ternary mixtures based on the use of surfactant and different salts in aqueous solutions that can form two different liquid phases. This characterization study was centered in the determination of several physical properties such as density, speed of sound, and refractive index. Also different derivative properties were calculated such as excess molar volume and isentropic compressibility. The present study analyzes aqueous binary mixtures in the homogeneous zone and also ternary mixtures (Tween20 + salt + water). This last kind of mixtures was studied in the homogeneous zone, analyzing the influence of surfactant and salt concentration and also phases in equilibrium. The influence of temperature upon the physical properties for homogeneous mixtures was also analyzed in the present work.