The influence of vapor velocity, reflux ratio, and the cycling parameters on the efficiency of a rectification column, operating under cyclic conditions, has been considered. Preliminary experiments using the ethanol-water system were performed to determine the optimum dimensions of the contact equipment with which subsequent investigations were carried out. The experiments showed that the bubble-cap plates without downcomers were less efficient than the plates having downcomers; they have considerable hydraulic resistance and are characterized by low capacity due to the prolonged liquid feed periods. For all the plates the efficiency increases with an increase of relative volatility of the mixture being separated. In all the tests the pressure drop under cyclic and otherwise similar conditions was less than under steady-state conditions.