Bulk Density by Tap Density Analysis
Bulk Density Introduction:
Bulk density is defined as the mass of the many particles of the material divided by the total volume they occupy. It is not an intrinsic property of a material; it can change depending on how the material is handled. Determination of Tapped Densities is a method to determine the bulk densities of powdered drugs under-tapped packing conditions. Tapped packing is defined as the state obtained when the vessel containing the powder sample is to be repeatedly dropped at a specified distance at a constant drop rate until the apparent volume of the sample in the vessel becomes almost constant.
How It Works:
Tapped bulk density is achieved by mechanically tapping a measuring cylinder containing a powder. After observing the initial volume, the cylinder is mechanically tapped, and volume readings are taken until little further volume change is observed (Figure 1).
Figure 1: A tapped density analyzerStrength of Tap Density Analysis:
- Cost-effective.
- Easily reproducible results.
- Standardized procedures.
Limitations of Tap Density Analysis:
Tap Density Analysis is sensitive to human errors.
Uses of Tap Density Analysis:
A tapped bulk density test is used to determine the required volume of small containers carrying a fixed mass of powder that has been compacted. The results of this test are primarily applicable to containers with volumes up to about one cubic meter.
Data:
The tap density data is given in the following equation:
TD = Weight of the sample/Volume of the sample in the cylinder after tapping
Sample Requirements:
Samples can be powders, granules, or other “divided” solids. In general, the samples should be tested in the as-received condition. In certain instances, the powder may be dried. However, if the powder is susceptible to oxidation, the powder is dried in a vacuum or inert gas. Powders containing volatile substances are not dried at all.
