Simultaneous development of macro- and micromixing in confined axis-symmetric reacting flows has been determined experimentally. Mixing of aqueous solutions of acid (internal jet) and base (coflow) with the coflow-to-jet flow rate ratio Q = <(V)over dot>(c)/<(V)over dot>(j) = 5.0, at which the velocity at the jet exit was higher than the co-flow one, was examined in a co-axial jet mixer. The two-color PLIF method was used: the dyes - sodium fluorescein and rhodamin B -were premixed to the jet. The reaction product concentration or molecular mixing was determined by measuring the radiated light intensity of sodium fluorescein. The fluorescence of rhodamin B highlighted turbulent transfer by vortices or mixture fraction development. Variations of reactant concentrations were calculated using the mass conservation equation and the simultaneously measured distributions of mixture fraction and chemical reaction product concentration. The analysis of mixing parameters showed a significant difference in the dynamics of turbulent and molecular mixing. (C) 2011 Elsevier Ltd. All rights reserved.