The design of reactive distillation columns requires the data for the phase and the reaction equilibrium. The phase equilibrium data for the binary reacting sub-system are difficult to get. A new apparatus has been constructed for reaction rates of half-life of 30 min. Data are presented for methanol with acetic acid and propionic acid at 60 degrees-90 degrees C. These temperatures represent the operation points of technical columns. (C) 1999 Elsevier Science B.V. All rights reserved.