What is bulk density, tapped density and how to measure them?

Bulk density refers to the mass of the bulk powder divided by the bulk volume. Bulk density can be calculated through the formula below:

where ρ_B is the bulk density, M is mass in grams, and V_B is the bulk volume in milliliters. The bulk volume includes the volumes of the  particle solid, interparticle voids, and pores in the particles.

The bulk density is greatly influenced by the spatial arrangement of powder particles. The tapped density value can be determined by mechanically tapping a container producing a regular vibration that rearranges the powder particles, thus reducing the volume of the interparticle voids. Hence with fewer voids, the tapped density is greater than the bulk density.

The calculation of the tapped density can be achieved using a tapped density tester after a regular vibration within a particular time.