Measurements of liquid velocities and liquid mixing have been performed in three different bubble columns of 0.15, 0.4 and 1 m diameter with water and air, at superficial gas velocity ranging from 0.05 to 0.20 m/s with high aspect ratios (H-D/D > 4). Liquid velocities are determined with a Pavlov tube calibrated up to 25% of gas holdup. Axial dispersion coefficient is determined using a new method which allows accounting for the upflow and downflow regions. The experimental results allow selecting reliable correlations of the literature. The Ueyama and Miyauchi model is successfully compared with the experiments and a new correlation for the kinematic viscosity is proposed. (C) 2003 Elsevier Science Ltd. All rights reserved.