Thermodynamics of sedimentation in paucidisperse systems

Abstract

The previously given treatment of sedimentation phenomena in monodisperse uncharged systems with the help of thermodynamics of irreversible processes is extended to paucidisperse systems. The sedimentation rates of the components are derived by neglecting transverse effects and by introducing the boundary condition of vanishing volume flow. The results are specified for ternary ideal mixtures and the sedimentation coefficients are expressed in terms of diffusion coefficients.

The obtained equations might account for two effects, established in experimental sedimentation study, viz., an anomalous behaviour of slowly sedimenting material above the boundary layer of more rapidly sedimenting components and the occurrence of a backward flow in experiments with the “synthetic boundary cell”, where slowly sedimenting materials are mixed with more rapidly sedimenting ones.