The settling velocities of aqueous slurries of praseodymium oxalate are well represented by the Maude-Whitmore equation in both the fairly dilute and very concentrated cases. Extensive channeling occurs in some slurries with intermediate concentrations, but not in other slurries at the same concentration. Thus, there is a duplicity of values rather than a transition. Aqueous slurries of calcium carbonate also follow the Maude-Whitmore equation at low and high concentrations. Extensive channeling occurs at intermediate values, but there is a region of instability rather than a duplicity of values. (C) 2013 Elsevier B.V. All rights reserved.