Layer formation of dilute colloidal suspensions as a result of a concentration dependent sedimentation velocity some simple considerations and suggestions for further experiments

In a number of experiments on sedimentation in colloidal suspensions, the formation of a vertically layered structure in the concentration profile has been observed. We argue that this may be interpreted as the formation of shock fronts in the concentration profile due to the concentration dependence of the sedimentation velocity, a mechanism first identified by Kynch. We propose several experiments to test this suggestion, and draw attention to the possibility of observing anomalous diffusion in a sedimenting suspension with reversible aggregation.