A numerical experiment has been carried out to find a theoretically sound correlation relating mean bubble diameter in the main section of a bubble column to the liquid physicochemical properties (density, viscosity, surface tension), and the superficial gas velocity. A correlation has been proposed in the form: d(32) = 0.289 rho(L)(-0.554) mu(L)(-0.048) sigma(0.442) U-G(-0.124) or, in an approximate, dimensionless form: Fr = 0.6(U(G)(4)rho(L)/g sigma)(1/2) The values obtained from the above correlations are in good agreement with experimental values, obtained for seven organic liquids. (c) 2005 Elsevier B.V. All rights reserved.