Measurements of bubble diameter and gas holdup for the nitrogen-water system were carried out in a vertical pilot plant column 0.3 m diameter and 4 m height. The process parameters were varied in the range: temperature 30-160 degrees C, pressure 0.1-1.1 MPa, dry gas flow rate 0.02-0.12 kg/m(2) s (saturated superficial gas velocity 0.002-0.020 m/s). Making use of the experimental values of the gas holdup and bubble diameter the values of interfacial area were calculated.