19-01U

A previously elaborated technique for constructing the equation of state of a cell fluid model in the high-temperature region (T>T_c) is generalized to the case of T<T_c. The grand partition function, thermodynamic potential and equation of state of the model are calculated within the framework of the collective variables method, taking into account the non-Gaussian (quartic) distribution of order parameter fluctuations. A nonlinear equation which links the density and the chemical potential is presented and solved analytically. Graphs of the dependence of the density on the chemical potential are obtained for various values of the relative temperature.