Definition of Porosity:
- Porosity is the fraction of void space (air) in a powder bed relative to its total volume.
$\varepsilon = \frac{V_{b} – V_{s}}{V_{b}} \times 100 \; \text{(Porosity)}$
- Where:
- Vb = Bulk volume (total volume occupied by powder, including voids)
- Vs = True volume (volume of the solid material itself)
Alternatively,
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$\varepsilon = 1 – \tfrac{\rho_{b}}{\rho_{t}}$
- Where:
- ρb = bulk density
- ρt = true density
Importance:
- High porosity = more air spaces → affects flow, compressibility, and tablet porosity (which in turn affects disintegration and dissolution).
