One advantage of this simple model is that in the rare gas limit, Nb<<V, it reduces back to the microscopically-justified Equation (???). (To verify this, it is sufficient to Taylor-expand t...One advantage of this simple model is that in the rare gas limit, Nb<<V, it reduces back to the microscopically-justified Equation (???). (To verify this, it is sufficient to Taylor-expand the right-hand side of Equation (???) in small Nb/V<<1, and retain only two leading terms.) Let us explore the basic properties of this model.