Two new graphical methods are presented for the calculation of equilibrium stages (N_D) for countercurrent extractors in which hackmixing is the only controlling factor for mass transfer.
Both proposed methods are based on a stagewise model with back-flow. One method is developed for the calculation of N_D for one-solute distribution and the other is developed for two dependent solutes distribution. The proposed graphical solutions for the two methods are different, but both can be straight-forwardly applied to the case of equilibrium distribution.