A phenomenological approach towards description of the Esin-Markov effect is developed based on the Frumkin isotherm in which the adsorption energy is a linear function of the electrode charge. It is shown that in this case, the discreteness factor λ found from the limiting slope of the dependence of the zero charge potential on the logarithm of surface-active anion concentration agrees with the value of λ obtained based on the dependence of the surface excess of cations on the electrode charge q at high positive q values. The expressions derived to describe the relationship between the discreteness factor and the adsorption parameters of Frumkin isotherm are used in interpretation of the discreteness effects at the adsorption of Cl−, Br−, and I− anions on interfaces of liquid electrodes based on Ga and alloys In-Ga and Tl-Ga with the solutions of salts in N-methylformamide.