Tap Density Tester
Taps a graduated cylinder of powder a set number of times from a fixed height so the bed packs down. The starting and final volumes give bulk density, tapped density, Carr's index and Hausner ratio.
- Pharmaceutical
- Nutraceutical
- Chemicals
- Food & beverage
- Powder metallurgy
Test your Tap density tester knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. Bulk density is calculated as:
basicQ2. Tapped density is always:
basicQ3. V0 = 120 mL and Vf = 100 mL. What is the Hausner ratio?
intermediateQ4. Using the same data (V0 = 120 mL, Vf = 100 mL), Carr's index is:
intermediateQ5. A Carr's index of 30% indicates flow that is:
intermediateQ6. In USP <616> method 1, the typical drop height of the cylinder is:
advanced
Viva questions
Think of your answer first, then open it to compare.
1. Why is the sample sieved before measuring bulk density?
Powders form loose lumps in storage. Sieving through about 1 mm breaks these up so the sample is in a reproducible state and the result reflects the powder, not its storage history.
2. What does a large difference between bulk and tapped density tell you about a powder?
It means the powder packs down a lot when tapped, so inter-particle friction and cohesion are high. Such powders usually flow poorly, fill dies and capsules unevenly and may need glidants or granulation.
3. Why must the cylinder not be knocked while filling?
Any knock settles the powder before V0 is read. V0 becomes smaller, bulk density higher, and Carr's index and Hausner ratio lower, so the powder appears to flow better than it really does.
Keep every Tap density tester in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.