A combined system has been devised with a liquid-liquid extraction-re-extraction reactor where the extraction compartment and the re-extraction compartment are put in contact with one another through the organic phase composed of an extractant and a diluent. We have applied this process to a system of chromium-sulfuric acid-tri-noctylamine-kerosene-ammonium carbonate. Interesting results were obtained for diluted solutions (100 ppm). A physical modelling of the extraction-re-extraction reactor demonstrated the existence of transfers that find their origins, on the one hand, in a gradient of potential chemicals, and, on the other hand, in the active transports bound to the coupled processes. The modelling of the reactor identified three phases: the first phase, where the transferred quantities are weak; the second phase, where the transferred quantities are important, such as pumping; and a third phase, which was much slower. The membrane works due to the "activation" by the co-solute of the transporter at one interface and to the "deactivation" at the other interface. Both of these active transport mechanisms created a real "chemical agitation".