The experimental study that concerns the extraction of alkali picrates with the bis-crown-6-calix[4]arene in a hollow fibers membrane contactor, validates a dynamic model described in a previous paper [D. Trébouet, Sep. Pur. Tech., 50, 97-106, 2006]. The experimental data confirm the influence of parameters as the aqueous and organic phase flowrates and module capacity factor on the sensitivity of the system. It appears clearly that the closed extraction system operates in an unsteady state until equilibrium is reached and so only dynamic models can represent mass transfer within reasonable accuracy. The overall mass transfer coefficient is determined even in the case where the equilibrium is described by a non-linear distribution isotherm. The determination of an overall mass transfer coefficient shows that the diffusion of the metal complex in the microporous is the main limiting step of mass transfer.