  A closed virial equation-of-state for the low density fluid phase of hard
disks is obtained from the known virial coefficients. The equation exhibits
6-figure accuracy for the thermodynamic (MD) pressure up to the reduced number
density ~ 0.4 Interpolation of the discrepancy at higher densities indicates a
higher-order thermodynamic phase transition at the extensive-intensive
free-volume percolation transition previously located by Hoover et al. (JCP 70
1837 1979)
