Two phase flow co-current horizontal spray column performing under high gas velocities (up to 14 m/s) is investigated in an air-water system. Experiments are carried out in order to characterize mass transfer between liquid and gas in the reactor under various conditions of liquid and gas flow rates. The mass transfer parameters studied are the interfacial area (a), the liquid volumetric mass transfer coefficient (k(L)a) and the liquid mass transfer coefficient (k(L)). The method of gas/liquid absorption with chemical reaction using sodium sulphite was applied to determine the interfacial area and the volumetric mass transfer is determined experimentally by a 'gasing out' method. (C) 2004 Elsevier B.V All rights reserved.