An experiment aimed to link the extent of axial mixing in a special configuration bubble column reactor with different liquid properties (water, 10% K2CO3 solution, 20% K2CO3 Solution, paraffine). The experimental results proved that, increase of liquid viscosity will delay the mean residence time and weaken gas axial backmixing. Increased surface tension leads to lower flow regime transition point and higher overall gas holdup. Surface tension is the dominant factor to influence of gas axial backmixing degree. A simple RTD model for homogeneous-heterogeneous regime is developed in the column of 0.1 m diameter and the corresponding correlation of gas axial dispersion coefficients is D-ag = 0.8u(g)(1.89)((rho L)/(rho w))(3.22)((1 -epsilon(g))(4)/epsilon(g)). The model is verified by experiments with air/water/paraffine system. Good agreement is found. As a byproduct, a non-empirical formula for gas holdup results, epsilon(g)/(1-epsilon(g))(4) = 0.579 (u(g)mu/sigma)(0.918) (mu(4)g/rho(L)sigma(3))(-0.252). But both correlations cannot be available for K2CO3 solution with addition of small quantities of surface tension in pure liquid. (C) 2008 Elsevier B.V. All rights reserved.