Use of the recording powder flowmeter for the qualitative evaluation of nonuniform flowing formulations and additional instrumentation for the quantitative measurement of the variation are described. This additional refinement prints out the time, in hundredths of a minute, for preselected weight increments of powder to flow from a hopper. The variation in time is a measure of the uniformity of flow. To illustrate the utility of the instrument, two formulations having similar average flow rates but differing in their uniformity of flow were tableted. The nonuniform flowing formulation tableted on a single-rotary press had a higher coefficient of intertablet weight variation and did not conform to USP standards. Both formulations were tableted on a double-rotary press equipped with induced die feed and low coefficients of variation were obtained in both instances indicating that the die feed mechanism was effective in minimizing intertablet weight variation of an irregularly flowing formulation.
LUCTUATING FLOW properties of tablet and F capsule formulations have been generally overlooked in studying such formulations or at best, evaluated only very subjectively. This has been due, quite largely, to the fact that the two general methods used to evaluate flow of powders, angle of repose measurement, and timed delivery through an orifice, do not distinguish irregularly flowing materials from those which flow smoothly and consistently. For example, Gunsel and Lachman (1) in comparing the flow of formulations prepared with conventionally processed and spray-dried lactose using timed delivery