The extended UNIQUAC electrolyte activity coefficient model has been correlated to 751 experimental solid-liquid equilibrium (SLE), vapor-liquid equilibrium (VLE), and excess enthalpy data for the mixed solvent CO2-NaHCO3-Na2CO3-monoethylene-glycol(MEG)-H2O electrolyte system. The model was validated by predicting the excess heat capacity. The model is consistent, and one set of binary interaction parameters are Used for Calculating all the properties between -50 and 90 degrees C. The model is compared to experimental data of infinite dilution activity coefficient Measurements of MEG and may be used For calculating activities, Solubility, salt hydrate properties. pH. and CO2 Solubility in the NaHCO3-Na2CO3-MEG-H2O system. A simple density model of NaHCO3-Na2CO3-NaCl-MEG-water is given.