Autoprotolysis in water/methanol/NaCl ternary systems

Abstract

A potentiometric method was used to determine the autoprotolysis constant for aqueous solutions containing 0, 20 and 40 mass % of methanol over a wide range of NaCl concentrations at 25 °C. The ionic strength ranged between 0.25 and 2.00 mol L -1 at intervals of 0.25 units. The osmotic and activity coefficients of the mixed solvents were calculated as a function of ionic strength. The dependence on ionic strength was analyzed using the ori.- ginal specific ion interaction theory. The specific ion interaction parameters associated with the thermodynamic autoprotolysis constant were extracted. Results indicate that interaction between ions increases with increasing metha- nol content in the mixture.