The applicability and the properties of the constants of the following equation on the number of tappings and the apparent bulk density of the powder were studied.
The equation is [function], where, n is the number of tappings, po, pf and pn are the apparent bulk densities of the powder at n=0, ∞ and n respectively, and k is a constant. 
When the particle size of the powder becomes large and the powder is easy to flow, pf and k  become large. On the contrary, when the tapping strength is increased, pf becomes larger but k becomes smaller.
In the packing procedure of the powder which has relatively large flocculated particles, the process separates into two steps with large and small k values. The former is the packing of the flocculated particles and the latter is the packing which is accompanied with the destruction of the flocculated particles.
The equation is also true about the tapping of the powder which is loosely settled in liquids. In this case, the value of k is small, and the process is considered to be the destruction of the flocculated particles in liquids.