A free turbulent jet discharging into a tank is a simple device and can develop local turbulent energy dssipation rates on the order of 10(3)-10(4) W kg(-1), which are suitable for fast reactions and drop dispersion. Parameter estimation For an earlier model of micromixing and mesomixing has been updated to include further information on turbulence in the initial developing region of the jet. Measured product distributions for fast chemical reactions, employing various initial jet velocities, viscosities and feed times for semi-batch operation, showed two limiting regimes where either micromixing or mesomixing was controlling. The updated model described these measurements satisfactorily, as well as some earlier drop breakup experiments.