Abstract: The rectifier having inserts for evaporation and condensation is constructed on the basis of modules (19). Each module has a distributor channel (5) for the liquid. The distributor channel (5) is positioned above the upper rim of an evaporater (1) inclined in the direction of the module axis. The evaporator (1) ends above a guide element (13) for the liquid. The guide element (13) is inclined in the direction of the module wall (14) and ends above the distributor channel (5) of the next module. The module is furthermore provided with a guide element (2) for the vapor and a condenser (10). The condenser (10) has drain elements (11, 15) for the condensate.