A profound theoretical analysis is presented of the four layer complexation model assuming that adsorbed anions and cations are located in two distinct layers, The theoretical relations between the intrinsic complexation constants. developed in our previous paper (Langmuir 1995, 22, 3199) are subjected to an exhaustive numerical analysis, along with the newly developed relation between PZC and IEP. That analysis shows that the dependence of the electrical capacitances in the system on the activity of the bulk electrolyte is of crucial importance for the behavior of these systems.