Based on the fundamental theory of interfacial energy in parts 1 (J. Colloid Interface Sci. 1996, 181, 259; 1996, 183, 299), 2, and 3, theoretical formulas have been derived for the specific interfacial energy gamma of solid-liquid interface changing with adsorption of the constituent anions or cations of the solid and foreign adsorbates to different crystal faces. Adsorption isotherms of silver and halide ions and experimental results for gamma obtained from potentiometry of silver ions on the basis of the Gibbs-Thomson effect in AgCl, AgBr, and AgI sol systems under the influence of the adsorption of the constituent halide ions and gelatin were analyzed in light of the theoretical formulas. Finally, the characteristics of the adsorption behavior of these species including the slight deviations from the theory have been discussed.