Within the framework of the model of a dense part of an electrical double layer as three parallel capacitors coupled with a set of Frumkin adsorption isotherms, equations are derived for simulating coadsorption of two solution components (neutral and ionic species). The adsorption behavior of model systems n-C4H9OH + NaCl (A) and 1-AdOH + NaCl (B) is analyzed and the results of estimation are compared with experimental data. It is concluded that, from the height of anodic capacitance peak (for the system A) and the shape of capacitance curve near the anodic phase transition potential (for the system B), certain conclusions can be drawn regarding the value of lateral interaction between surface-active ions and organic molecules, if the parameters of their individual adsorption are known. A general agreement is found between experimental results and simulated ones.