This device allows a simple approach to material transfer. It consists mainly of a column with wet discs. Water trickles down this column, while air is flowing countercurrently. In contact with the disks, the air becomes moist and the coefficient of material transfer between the liquid and the gas is calculated simply from the measurement of the air flow and its humidity. The water content of the air is determined by means of a hygrometer. The air and water flow rates as well as the dry and humid air temperatures and the water temperatures at various points of the apparatus are measured.