Using a modified extraction cell of Lewis type, the limiting steps of the Penicillin G physical extraction with butyl acetate and reactive reaction with Amberlite LA-2 were established. Two types of calculation of the values of mass transfer coefficients and potential for each extraction system were used. The established mathematical correlation between mass flow and mass transfer coefficient of Penicillin G with Re and SC numbers, or rotation speed, offer a good concordance with experimental data. Finally, the kinetics of the reactive extraction of Penicillin G with Amberlite LA - 2 was studied and the specific reaction rate was determined: k(1) = 5.927.10(-4) dm(3) mol(-1) s(-1). In comparing with the experimental data, this value offers an average deviation of 4.04 %.