Based on the appearance of minima of the free energy of mixing and maxima (or minima) of excess free energy, the formation of metastable compounds and eutectics during rapid solidification of metallic melts as well as the presence of miscibility gaps in the phase diagrams of a lot of binary alloys, calculating models of mass action concentrations for Cd-Bi,Ge-Al; Bi-Sn, Cd-Sn, Ag-Cu, Al-Ga; Si-Ag, Pb-Sn and Al-Sn binary metallic melts have been deduced. Good agreement between- the calculated and measured values shows that the calculating models reflect the structural characteristics of given metallic melts.