Densities of Powders

• Densities of Powders explain bulk, tapped, and true densities influencing flow and packing.
• Densities of Powders determine formulation, compaction, and quality control in pharmaceuticals.

1. True Density (ρ_t)

• The density of the actual solid material, excluding pores or voids.
• Measured using a helium pycnometer or liquid displacement.
• Units: g/cm³

$\rho_{t} = \frac{\text{Mass of particles}}{\text{True volume } (V_{s})}$

2. Bulk Density (ρ_b​)

• The mass of powder per bulk volume, which includes air spaces between particles.
• Determined by pouring powder into a graduated cylinder.

 $\rho_{b} = \frac{\text{Mass}}{\text{Bulk volume } (V_{b})}$

3. Tapped Density (ρ_tap​)

• Measured after tapping the powder container (usually 500–1250 taps).
• Represents the maximum packing that can be achieved without compression.

$\rho_{\text{tap}} = \frac{\text{Mass}}{\text{Tapped volume}}$

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