Vapor-liquid equilibrium data at atmospheric pressure were obtained for the acetic acid-water system containing magnesium nitrate, cupric nitrate or cadmium nitrate of various concentrations. These data were obtained with a view to ascertaining the possibility of separating acetic acid and water under condition of reversed relative volatility by extractive distillation with increasing salt concentration. The results show a considerable effect of magnesium nitrate or cupric nitrate addition, with a reversal taking place at approximately 10 weight % magnesium nitrate, and 11 weight % cupric nitrate in the liquid phase. A method of graphical representation which is facilitated the interpolation of salt concentration is proposed, and the data is examined by the simple empirical equation which correlates the salt effect.