The paper presents the calculation results on the construction of solidus lines of phase diagrams for some binary metal systems based on cadmium, zinc and tellurium. The investigations have been carried out using the phase equilibrium thermodynamics and known liquidus lines. By the calculation method the solidus lines of phase diagrams of the Cd-Na, Cd-Tl, Te-Ga, Te-As, Te-Cu and Zn-Sn systems were constructed in the temperature range from the base component melting point to the eutectic transformation temperature. In the Cd-Tl, Te-As, Te-Cu and Zn-Sn systems a retrograde solubility of the second component in the solid phase was observed. The temperature and maximum solubility values at the retrograde behavior of solidus lines, as well as, the limiting solubility values of components at eutectic transformation in the systems based on Cd, Zn and Te were determined.

In the region of the primary solid α-phase for systems with limited solubility thermodynamic quantities such as the partial enthalpy of dissolution  B H  , the activity coefficients   В and the activities  B a in binary metal systems were calculated. The above mentioned indicated values were determined from the relations that connect these parameters with the equilibrium distribution coefficient k 0B and known thermodynamic quantities, such as the enthalpy variation mВ H  and entropy variation mВ S  during melting of component B. The calculation of equilibrium distribution coefficients using data from experimentally constructed solidus and liquidus lines of state diagrams was performed. The values and temperature dependences of the dissolution enthalpy for such systems as Ag-Mg, Nb-Ge, Mg-Al, Mg-Ag, Al-Mg, Ni-Ga, as well as the values and dependences of the activity coefficients   В and activities  B a of the second component on these systems were determined.

In this work the computation of the equilibrium k0 and limiting k0limB distribution coefficients (DC) of the components according to the state diagrams of binary metal systems Mg–Ag, Ag–Mg, Al– Mg, Mg–Al, Ni–Ga, and Nb–Ge was achieved. These systems belong to systems with limited solubility and for them the approximating equations of the solidus and liquidus lines are obtained in the form of second-order polynomials in the temperature range from the melting point of the main component TMA to the eutectic temperature TEA. A mathematical analysis of the obtained equations for calculating DC is performed. For the first time by calculated and graphical methods the values of the limiting distribution coefficients k0limB for such systems as Mg – Al, Mg – Ag, and Al – Mg were determined. The complete coincidence of the k0limB values obtained by different methods is confirmed. For the Ag–Mg, Nb–Ge and Ni–Ga systems adjusted values of the limiting coefficient were obtained, which are in good agreement with the reference values. The dependences of the equilibrium distribution coefficients on temperature and concentration for the investigated systems are constructed. In the studied temperature range from TMA to TEA, a linear dependence of the distribution coefficients on temperature and concentration is observed.

The results of calculating the Peclet number Ре = wr/(ρD) (where D is the diffusion coefficient; w is the evaporation rate of the substance; ρ is the density of the substance; r is the size factor) in sublimation processes of simple substances with high values of vapor pressure (≈ 1 mm Hg and above at the melting temperature): As, Gd, Tm, Lu, Cr, Yb, Sm, Mg, Ra, Ca, Sr, Ni, Co, Eu, Mn, Ba. It is shown that the nature of the temperature dependence Pe(T) is determined by the properties of the components of the sublimated system “base–impurity” (including the diffusion activation energy Q of impurity). For each substance for given Q and r, the dependence Pe(T) is monotonic. A decrease in the process temperature can improve the purification of a substance from one of several impurities, accompanied by deterioration in the purification from another impurity.

The method for determining the thermodynamic quantities: the partial enthalpy of dissolution , the activity coefficients and activities of the second component B in binary metallic systems with low solubility in the solid α-phase has been proposed. The algorithm for determining the above values is a sequence of preliminary calculations of the limiting and equilibrium distribution coefficients and construction of saturated solid solution lines for such systems with low solubility of the second component. Preliminarily obtained data are necessary for determining the partial enthalpy of dissolution and other quantities in the systems under study. Such a sequence of calculations is the proposed method for determining the thermodynamic parameters of dissolution. The values and temperature dependences of the dissolution enthalpy of component having a low solubility for such systems as Cd-Na, Cd-Tl, Te-Ga, Te-As, Te-Cu, Zn-Sn, as well as the activity coefficients and the activities of the second component in the saturating α-phase in these systems were determined. An analysis of obtained results on the enthalpy of dissolution shows that a change in the partial enthalpy with a change in the dissolution temperature is observed. When the temperature decreases from the melting point of the pure main component to the eutectic temperature, an increase in the partial enthalpies of dissolution of the second component is observed for studied systems. The Te-Ga system is characterized by a negative value . A negative value indicates an exothermic process of gallium dissolution in tellurium, in contrast to other systems in which the dissolution of the second component occurs with heat absorption. Analyzing the enthalpy of dissolution in the systems under study, it should be noted that the low values of < 2000 J/mol are characterized by the systems Cd-Na and Te-Ga. For systems Te-Cu, Te-As, Te-Tl, Zn-Sn > 15000 J/mol. Systems with a value > 15000 J/mol reveal a tendency to the occurrence of retrograde solubility in them. The difference in values is found to be more than two orders of magnitude for different systems.