Earlier work with silica sand has indicated that in a system where a bed of particles is aerated at increasing superficial velocities, the von Neumann ratio, T based on the bed pressure drop, may be useful in identifying both minimum fluidizing velocity, U-mf, and minimum bubbling velocity, U-mb, Plots of T-1 against superficial velocity exhibited significant change at velocities consistent with those where bed height first changed (onset of fluidization), the packed bed pressure drop underwent a transition from a monotonic linear function of superficial velocity to a steady value (onset of fluidization) and standard deviation of bed pressure drop rapidly increased (onset of bubbling). However, the suggestion that T might be a valid indicator of U-mf was supported by data for a single material only. In this paper additional data is presented that supports the suggestion that T might be useful in measuring U-mf, and also provides additional evidence for the potential utility of T in determining U-mb. In principle, this would allow a single campaign of pressure measurements to be used to identify both U-mf and U-mb. (c) 2009 Elsevier B.V. All rights reserved.