The thermodynamic property of HCl-NaCl-C2H6O2-H2O system were studied by means of emf measurement in the cells without liquid junction Pt，H2(105Pa )│HCl(m)，C3H8O3(w)

H2O (1-w)│AgCl-Ag (A) Pt，H2(105Pa )│HCl(mA)，NaCl(mB)

C3H8O3 (w)

H2O (1-w)│AgCl-Ag (B) at a constant ionic strength I=1.00 mol8226;kg-1 and mass fraction of glycol in the mixed solvent

equating to w=5%

15% and 20%

respectively

at temperature ranging from 278.15 to 323.15K.The standard electrode potential of Ag-AgCl in the mixed solvent were determined from cell (A).The activity coefficients of HCl γA in the mixed solvent system were determined from cell(B).The results show that the activity coefficients of HCl in HCl-NaCl solutions still obey the Harned’s rule and lgγA is a linear function of the reciprocal of the absolute temperature at constant composition of the mixture.Relative molar enthalpies of HCl LAare linear function of the ionic strength fraction of NaCl at constant total ionic strength and temperature.The standard transfer Gibbs free energies of HCl from water to mixed solvent were calculated.