  The interpretation of the linear character of the observable classic
rectilinear diameter law and the linear character of the Zeno-line (unit
compressibility line Z=1) on the basis of global isomorphism between Ising
model (Lattice Gas) and simple fluid is proposed. The correct definition of the
limiting nontrivial Zeno state is given and its relation with the locus of the
critical point is derived within this approach. We show that the liquid-vapor
part of the phase diagram of the molecular fluids can be described as the
isomorphic image of the phase diagram of the Lattice Gas. It is shown how the
the position of the critical points of the fluids of the Lenard-Jones type can
be determined basing on the scaling symmetry. As a sequence the explanation of
the well known fact about "global" cubic character of the coexistence curve of
the molecular fluids is proposed.
