Hydrolysis of butyl acetate leads to great losses of the solvent at the RAS Kiviter dephenolization plant. The rate of the acid hydrolysis for butyl acetate is studied by alkalimetric titration of acetic acid formed in two-phase systems. The rate of the alkaline hydrolysis is studied by pH-rate profiles in one-phase aqueous solutions and by the concentration of the acetate anions revealed in two-phase pH-buffered systems. The temperature dependencies for the rate constants and for the pH value, providing the minimum hydrolysis, are described.