The liquid-liquid mass transfer properties of two inline high shear mixers (HSMs) were investigated by the liquid-liquid extraction (LLE) method using the water-benzoic acid-kerosene system. The characteristic parameters of the extraction efficiency (E) and volumetric mass transfer coefficient (K(L)a) were measured under different conditions involving the rotor speed, two liquid phase flow rates, and surfactant concentration. The results indicate that both E and K(L)a increase with the rotor speed and aqueous-phase flow rate. The value of E decreases sharply but K(L)a increases slightly with the organic phase flow rate. Both E and K(L)a increase first and then decrease with the surfactant concentrations. Dimensionless correlations for the Sherwood number were obtained to provide guidance on the optimization and scale-up design of these kinds of inline HSMs. (C) 2015 Elsevier B.V. All rights reserved.