Abstract: After investigation on the thermodynamic properties of a small number of binary metallic melts, the structural units of which cannot be wholly determined by the corresponding phase diagrams, it was found that they can be determined by the principle of annexation of two kinds of solutions in binary metallic melts. According to the principle of annexation, calculating models of mass action concentrations for several binary metallic melts have been formulated. The calculated results agree well with practice, showing that this principle is a reliable basis for determination of the structural units for some binary metallic melts.

Key words: metallic melt, annexation, activity