We investigate the sedimentation equilibrium of a charge stabilized colloidal
suspension in the regime of low ionic strength. We analyze the asymptotic
behaviour of the density profiles on the basis of a simple Poisson--Boltzmann
theory and show that the effective mass we can deduce from the barometric law
corresponds to the actual mass of the colloidal particles, contrary to previous
studies.Comment: 13 pages, 4 figures, 1 tabl
