  We investigate the Equation of State (EOS) of classical systems having 300
and 512 particles confined in a box with periodic boundary conditions. We show
that such a system, independently on the number of particles investigated, has
a critical density of about 1/3 the ground state density and a critical
temperature of about $2.5~ MeV$. The mass distribution at the critical point
exhibits a power law with $\tau = 2.23$. Making use of the grand partition
function of Fisher's droplet model, we obtain an analytical EOS around the
critical point in good agreement with the one extracted from the numerical
simulations.
