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Kinetic studies of the extraction of chromium(VI) [Cr(VI)] from the hydrochloric acid solution with tri-n-octylamine (N235) have been mad by a Lewis cell. The influences of various kinetic parameters, such as stirring rate, interfacial area, temperature, N235 and initial Cr (VI) concentrations were evaluated. The rate equations for the extraction of Cr(VI) by N235 were obtained on the basis of the slop analysis data. The results indicated that the reaction rate of Cr (VI) increased with increasing of the stirring rate and interfacial area until that a "plateau" was observed with increasing stirring rate. The activation energies of Cr(VI) extraction by N235 dissolved in diluents were calculated. Kinetics analysis proved that the mass transfer was controlled mainly by diffusion and the chemical reaction between Cr(VI) anions and N235 could be achieved at the liquid-liquid interface. On the basis of the relation between ln[Cr(VI)] and ln R0 or ln[N235] and ln R0, the rate equations can be obtained. This research provides a proof-in-concept analysis for kinetic mechanism. [ABSTRACT FROM AUTHOR]