Thermodynamic limitations on the Gibbs energy, following from the thermodynamic stability condition of thermodynamic stability, are considered. Estimation of the possible values of the excess Gibss energy ΔG^E or the Gibbs energy of mixing ΔG^M of ternary solutions from data on binary solutions allows determination of the maximum possible (limiting) values of ΔG^E and ΔG^M. Examples of calculations for some ternary liquid-phase systems are given.