Measurements of gas hold-up for the nitrogen-water system were carried out in a vertical pilot column 0.3 m in diameter and 4 m high. The process parameters were varied in the ranges: temperature 30-160 degrees C, pressure 0.1-1.1 MPa, dry gas flow rate 0.02-0.12 kg/(m(2).s). Making use of the experimental values of the gas hold-up and the experimental values of bubble diameter [1] the values of interfacial area in a pilot column were calculated.