  We propose a method for describing a phase behavior of a system consisting of
particles of two sorts. The interaction of each species is described by
interaction potentials containing the repulsive and attractive components.
Asymmetry is ensured by different values of the interaction potentials of each
sort. The grand partition function of a binary mixture is calculated in the
zero-mode approximation A line of critical points, which correspond to
different proportions of the components, is calculated for specific values of
parameters of the interaction potential. We have obtained an equation that
relates the introduced mixing parameter x with the concentration of the fluid.
An explicit expression of the pressure of the binary mixture is derived as a
function of relative temperature and mixing parameter x to plot the Widom line.
It is established that for boundary values of this parameter (x = 0 and x = 1),
the equation of state of a mixture turns into equations of state of its
separate species.
