Phase equilibria for the NaCl/ KCl-PEG400-H 2 O aqueous ternary systems at 298 K were stud-ied using an isothermal dissolution method. In addition,the densities and refractive indices were deter-mined. The corresponding phase diagrams,as well as the density vs. composition and refractive index vs. composition diagrams,were plotted. Results revealed that over the entire PEG400 composition range studied at 298 K only 1 liquid phase was obtained,without the formation of a biphase region. The phase diagrams of these 2 systems consist of 1 homogeneous area with unsaturated liquid (L)and an equilibri-um area containing the solid phase of NaCl/ KCl and the saturated liquid phase (S + L). The solubility of NaCl/ KCl decreases with the addition of PEG400 at 298 K.