During the initial phases of the Ferrocyanide Safety Program, it was presumed that actual sludge in tanks would behave as if it were a two-phase system in which a brine phase would seep through the insoluble solid phase of ferrocyanide and other precipitated salts. After flowsheet materials were produced and extensively tested, it became apparent that the ferrocyanide precipitates held extensive quantities of water (50% by weight or more) that were far above what would be expected from hydrated salts. Because little or no draining of this fluid occurred over a period of months, it was concluded that the precipitates and their solution would act as a homogeneous single phase in much the same way as natural clays. Suggestions were made that the testing of clays could add to existing knowledge of sludge hydraulic and rheologic properties, at a much-reduced cost in chemicals and time over that required for flowsheet materials. Tests were conducted in a 400-L volume of ferrocyanide sludge simulant to determine thermal characteristics around heated zones. At low heat loads, surface vapor losses were much lower than return rates, resulting in no net change in water content. Under boiling conditions, no bulk dryout occurred. These results weremore » consistent with the results from earlier small-scale experiments.« less