Application of equations of mixing thermodynamic parameters formulated on the basis of the coexistence theory of metallic melts in Ba-Al, Mg-Al, Sr-Al and Cu-Al melts leads to fruitful results that not only the evaluated mass action concentrations agree well with the measured activities, but also the calculated mixing thermodynamic parameters are quite coincident with the experimental values. Moreover, the calculated mass action concentrations strictly obey the mass action law. The evaluated mixing thermodynamic parameters have very fine regularity: the mixing free energy is composed of standard free formation energies of all compounds and chemical potentials of all structural units at equilibrium; the mixing enthalpy consists of standard formation enthalpies of all compounds; the mixing entropy is composed of standard entropies of all compounds and configuration entropies of all structural units at equilibrium. As the equations of mixing thermodynamic parameters formulated are widely applicable to metallic melts involving compound formation, they can be used as the second practical criterion to determine whether thermodynamic models of metallic melts are correctly formulated. Application of equations of mixing thermodynamic parameters formulated on the basis of the coexistence theory of metallic melts in Ba-Al, Mg-Al, Sr-Al and Cu-Al melts leads to fruitful results that not only that evaluated mass action concentrations agree well with the calculated activities, but also the calculated mixing thermodynamic parameters are quite coincident with the experimental values. the calculated mass action concentrations strictly obey the mass action law. The suggested mixing thermodynamic parameters have very fine regularity: the mixing free energy is composed of standard free formation energies of all compounds and chemical potentials of all structural units at equilibrium; the mixing enthalpy consists of standard formation enthalpies of all compounds; the mixing entropy is composed of standard entropies of all compounds and configuration entropies of all structural units at equilibrium. As the equations of mixing thermodynamic parameters formulated are widel y applicable to metallic melts involving compound formation, they can be used as the second practical criterion to determine whether thermodynamic models of metallic melts are correctly formulated.