Thermodynamic functions of a two-component spatially homogeneous system near the critical separation point

In the vicinity of critical separation point the evident expression for free energy of double component isotropic system as the function of composition, temperature and Hamiltonian initial parameters is received. With $T\geqslant T_c$ the investigated system represents homogeneous mixture. With $T\leqslant T_c$ the sphere of free energy instability according to concentration is determined in which the component stratification takes place. The expressions for entropy and specific heat are also given.