  Critical phenomena in non-equilibrium systems have been studied by means of a
wide variety of theoretical and experimental approaches. Mode-coupling,
renormalization group, complex Lie algebras and diagrammatic techniques are
some of the usual theoretical tools. Experimental studies include light and
inelastic neutron scattering, X-ray photon correlation spectroscopy, microwave
interferometry and several other techniques. Nevertheless no conclusive
reatment has been developed from the basic principles of a thermodynamic theory
of irreversible processes. We have developed a formalism in which we obtain
correlation functions as field averages of the associated functions. By
applying such formalism we attempt to find out if the resulting correlation
functions will inherit the mathematical properties (integrability, generalized
homogeneity, scaling laws) of its parent potentials, and we will also use these
correlation functions to study the behavior of macroscopic systems far from
equilibrium, specially in the neighborhood of critical points or dynamic phase
transitions. As a working example we will consider the mono-critical behavior
of a non-equilibrium binary fluid mixture close to its consolute point.
