Abstract: Sugars are not only biologically important compounds but also typical nonelectrolyte with hydrophilic hydroxyl group, which are capable of hydrogen bonding. D-fructose is an important class of single sugar, and exists in human body with a certain concentration. D-fructose can be absorbed by cells directly. Chemists and biologists pay great attention to it, because of its importance in the research work of biochemistry. In this paper the thermodynamic properties of HCl-NaCl- C6H12O6-H2O system has been studied by EMF measurement in cells without liquid junction from 278.15 to 318.15 K Pt, H2(105 Pa)|HCl(m), C6H12O6 (w), H2O(1－w)|AgCl-Ag (A) Pt, H2(105 Pa)|HCl(mA), NaCl(mB), C6H12O6 (w), H2O(1－w)|AgCl-Ag (B) with the mass fraction of fructose w(C6H12O6)=2.5％、5％ or 7.5％ at a total ionic strength I=1.0000 mol•kg－1. The standard electrode potential of AgCl-Ag in the mixed solvent was determined for cell (A). The standard transfer Gibbs free energies, entropy and enthalpy of HCl from water to mixed solvent were calculated. The activity coefficients of HCl(γA) in the mixed solvent was determined from cell (B). The results show that the activity coefficients of HCl in HCl-NaCl solutions still obeys Harned′s Rule. The primary,secondary and total medium effect of HCl were calculated and discussed.

Key words: Activity coefficients, Harned′s Rule, EMF, Medium effect, Fructose