In this work, the isothermal solubility, density and refractive index of the {formamide (FA)/N-methylformamide (NMF)/N,N-dimethylformamide (DMF) + CsCl + water} ternary systems are determined at T = (288.15, 298.15 and 308.15) K and 0.1 MPa. The isothermal solubility is correlated by the NRTL model and UNIQUAC model. As the temperature is considered, a linear fitting equation of temperature is adopted here to fit the density and refractive index. The turbidity instrument is employed to investigate the solubility of the salt at multiple temperatures. Moreover, the related thermodynamic functions derived from the Van't Hoff equation were calculated. The mean activity coefficients of the (FA/NMF/DMF + CsCl + H2O) systems at T = (288.15, 298.15 and 308.15) K have been obtained as a combination of the thermodynamics and phase equilibrium through the UNIQUAC model. (C) 2014 Elsevier Ltd. All rights reserved.