Saturated vapor properties and scaling in the lattice gas model

A study of the lattice gas (Ising) model shows the properties of saturated vapor in coexistence with a liquid to be independent of the system's fixed mean density ρfixed, in keeping with standard thermodynamics. This behavior ensures that Fisher scaling plots are unique, independent of ρfixed, and yield a unique characterization of the liquid--vapor phase diagram. The resulting phase diagram and critical parameters for the square lattice gas model are shown to agree with accepted values to within a few percent throughout the coexistence region.