The apparent mass in sedimentation profiles of charged suspensions

Recent experiments have revealed that the exponential decay in the sedimentation density profiles of charged colloidal suspensions is governed by an apparent mass that is smaller than the buoyant mass. A simple analytical density functional study is presented which describes the reduction of the apparent mass. In accordance with experiments, it is found that the mass reduction depends on the concentration of added salt as well as on the colloidal sedimentation height.