The theory of mass transfer accompanied by chemical reaction for the pseudo-first-order heterogeneous liquid-liquid reactions was used to measure the effective interfacial area in a novel two-impinging-jets reactor (TIJR), which is characterized by a small reactor volume equipped with two simple nozzles directed toward each other. Aqueous and organic streams were jetted through the nozzles into rotating and stationary disks, resulting in a highly turbulent mixture of aqueous and organic phases. Experiments were also conducted on the physical extraction of n-Butyl formate into distilled water to measure the overall volumetric mass-transfer coefficients. Due to both the impinging process and high rate shear forces acting on the phases, the overall volumetric mass-transfer coefficients and volumetric extraction rates obtained by the physical and chemical method, respectively, increased dramatically compared to those obtained by conventional reaction systems and an air-driven two-impinging-streams reactor developed by the present author. The enhancing effect of impinging jets on the conversion of aqueous NaOH solution was tested by another nonimpinging-jets reactor.