The study of the phase and chemical processes in systems with reactions and stratification is important for the applied aspects of science and development of fundamental thermodynamic theory. For example these processes are rather wide applied in chemical technology and for development of industrial organic synthesis. The thermodynamic study of such a systems is of particular interest. A lot of previous studies of phase equilibrium provide data on the liquid-liquid and liquid-vapor equilibriums, but only a limited number of them consider the systems with a chemical reaction. The set of investigations of the liquid-liquid phase equilibrium with simultaneous chemical reaction is presented in the papers [1-2]. These works report data on the solubility (20, 30 and 40°C), the liquid-liquid phase equilibrium (20, 30 and 40°C), as well as the chemical equilibrium (20, 30ºC) for a system acetic acid - ethanol - ethyl acetate – water. Here we report the results of study of chemical equilibrium in this system at severa