The hydrodynamic behavior of a pilot plant Hanson mixer-settler extraction column has been studied for three different liquid-liquid systems with and without mass transfer conditions. The dispersed phase axial holdup profile is investigated and an empirical correlation for prediction of dispersed phase holdup is recommended in terms of physical properties of liquid systems and operating conditions. A comparison between several correlations and experimental results shows that Pratt equation is more suitable for prediction of slip velocity because of its simplicity. On this basis, an empirical correlation is derived for prediction of characteristic velocity in terms of physical properties of liquid systems and operating conditions. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.