An equation for the correlation and prediction of the vapor−liquid equilibrium of the water−acetic acid−calcium chloride systems at low pressures has been developed and fitted to experimental data. It is based on the hypothesis that the ternary system can be considered a binary system formed by two pseudocomponents: water + salt and acetic acid + salt. The equation, derived from Galan's equation, can calculate equilibrium data for the ternary system with a knowledge of only the equilibrium data for the water−acetic acid binary system and the vapor pressures of the pure components and the pseudocomponents.