Abstract: The salt effect parameters(from Furter's equation)of three electrolytes (NaCl ,NaBr, KCl) for various ethanol-water mixtures were determined by vapor-liquid equilibriumexperiments.Acalculation method of this parameter(K)by the scaled particle theory wassuggested.The term of hard sphere interactions was calculated by using Masterton-Lee's equation.and that of soft sphere interactions was treated by using Y.Hu's radial distributionfunction method, i.e.taking the first coordination shell as in order,and out of the shell asrandom mixing.The interactions between the charge of ions and dipole or induced dipole ofthe central molecule were considered effectively within the limits of the first coordinationshell,and the ions out of the shell were regarded as L-Jmolecules.In this paper a correlation equation for the located dielectrical constant and liquid concentration was proposed andthe predicted results of the salt effect parameters were in agreement with the experiments bythis equation.

Key words: Ethanol, Water, Vapor-liquid equilibrium, Salt effect parameter, Scaled particletheory