  We show that equilibrium monomer and centre-of-mass concentration profiles of
lattice polymers in a gravitational field, computed by Monte-Carlo simulations,
provide an accurate and efficient road to the osmotic equation-of-state of
polymer solutions, via a straightforward application of the hydrostatic
equilibrium condition. The method yields the full equation of state over a wide
range of concentrations from a single simulation, and does not suffer from
significant finite size effects. It has been applied to self-avoiding walk
polymer chains with nearest neighbour monomer attractions, from the good
solvent to the theta solvent regimes. The consistency of the method has been
carefully checked by varying the strength of the gravitational field.
