Page 18 - Pharmaceutics III_ 02-06-01304_Fall 2025_ Pharm D_Electronic book
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2.8 Flow Properties of Powders
Powder flowability affects mixing, capsule filling, and tablet compression.
Key parameters include:
1. Angle of Repose
The maximum angle between the surface of a powder pile and the horizontal plane indicates
flowability.
Lower angle → better flow.
Measured by allowing powder to flow through a funnel under gravity until a stable cone
forms.
2. Bulk and Tapped Density
Powder is poured into a graduated cylinder to obtain bulk volume. After tapping a set
number of times, the tapped volume is measured.
From these, we calculate:
• Hausner ratio = tapped density / bulk density
• Compressibility index (Carr’s Index) = [(tapped – bulk) / tapped] × 100
Smaller values indicate better flow.
2.9 Laboratory Practice
Students should be able to:
1. Measure flow parameters of powders using the angle of repose and tapped density
tests.
2. Calculate compressibility index and Hausner ratio.
3. Interpret results in terms of powder flowability and handling properties.
2.10 Summary
Micromeritics provides the foundational understanding of how particle properties influence
the behavior of pharmaceutical solids.
By mastering particle characterization techniques and derived parameters, pharmacists can
optimize dosage form performance, ensuring uniformity, stability, and therapeutic efficacy.
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