Importantance of bulk density

Sir can anyone tell me importance of bulk density and tapped density

Bulk density is an essential parameter for pharmaceutical product & process development and solid dosage manufacturing. It is used in determining the amount of powder that can fit in a space such as a blender or a hopper on a tablet press or capsule filler. It is also used to determine the amount of powder that can be fitted into a capsule which has specific volume.

One important characteristic is tapped bulk density, or simply tapped (tap) density: that is, the maximum packing density of a powder (or blend of powders) achieved under the influence of welldefined, externally applied forces. The minimum packed volume thus achieved depends on a number of factors including particle size distribution, true density, particle shape and cohesiveness due to surface forces including moisture. Therefore, the tap density of a material can be used to predict both its flow properties and its compressibility. These are just two of the many parameters which are important in the overall tabletting process - which requires that loose powders be compacted into a durable solid form with the correct mechanical strength, porosity and dissolution characteristics – and in capsule filling performance.

Because the interparticulate interactions influencing the bulking properties of a powder are
also the interactions that interfere with powder flow, a comparison of the bulk and tapped
densities can give a measure of the relative importance of these interactions in a given
powder. Such a comparison is often used as an index of the ability of the powder to flow, for
example the Compressibility index or the Hausner ratio.
The Compressibility index and Hausner ratio are measures of the propensity of a powder to be
compressed as described above. As such, they are measures of the powder ability to settle and
they permit an assessment of the relative importance of interparticulate interactions. In a freeflowing powder, such interactions are less significant, and the bulk and tapped densities will
be closer in value. For poorer flowing materials, there are frequently greater interparticulate
interactions, and a greater difference between the bulk and tapped densities will be observed.
These differences are reflected in the Compressibility Index and the Hausner Ratio.