Properties of Lattice and Continuum van der Waals Fluids at the Critical Point

A suggestion by Fisher that the specific heats of lattice gases and continuum fluids near the critical point be compared on the basis of specific heat measured in units of the volume per particle at close packing is examined for systems with hard cores and long-range attractive potentials (van der Waals systems). It is found that the discontinuity at the critical point in the specific heat so defined is indeed similar for lattice gases and continuum systems in one, two, and three dimensions, while the critical density varies widely. No explanation is offered. Numerical values of other critical constants are also given.