Question

Match the following: 
I. True density            (P) Reciprocal of bulk density 
II. Granule density     (Q) Graduated cylinder method 
III. Bulk density         (R) Helium Pycnometer 
IV. Bulkiness             (S) Mercury displacement method

• A. (I)-(S), (II)-(P), (III)-(Q), (IV)-(R)
• B. (I)-(Q), (II)-(S), (III)-(P), (IV)-(R)
• C. (I)-(R), (II)-(S), (III)-(Q), (IV)-(P)
• D. (I)-(S), (II)-(R), (III)-(Q), (IV)-(P)

Hint:

Bulk density and true density are crucial parameters in powder flow, compression behavior, and dosage form uniformity.

Answer 1

The Correct Option is C

Each type of density in pharmaceutical powders is determined using specific techniques: - I. True density refers to the density of the solid material excluding pores and voids. It is accurately measured using a Helium Pycnometer because helium gas can penetrate even the smallest voids in the sample. \hfill $\Rightarrow$ (R)
- II. Granule density (also called apparent or particle density) includes intra-particle pores and is often measured using the mercury displacement method, as mercury does not enter small pores. \hfill $\Rightarrow$ (S)
- III. Bulk density is the mass of a powder divided by its bulk volume (including voids). It is typically measured using the graduated cylinder method, where the powder is poured into a cylinder without tapping. \hfill $\Rightarrow$ (Q)
- IV. Bulkiness is the inverse of bulk density, i.e., volume occupied per unit mass of the powder. \hfill $\Rightarrow$ (P)
Thus, the correct matching is: I-(R), II-(S), III-(Q), IV-(P)

Answer 2

This question matches four density-related terms in pharmaceutics to the method used to measure or define each one. Working out the correct method for each term first, then checking which combination option matches that pairing, gives the answer.

1. (I)-(S), (II)-(P), (III)-(Q), (IV)-(R): This pairs true density with the mercury displacement method (S), but mercury cannot enter the very fine pores of a solid, so it is used for granule density, not true density, which needs a gas that can penetrate every pore. This combination also puts granule density with bulkiness (P) and bulk density with the Helium Pycnometer (R), neither of which matches how these are actually measured, so this option is wrong.
2. (I)-(Q), (II)-(S), (III)-(P), (IV)-(R): Here true density is paired with the graduated cylinder method (Q), which is actually how bulk density is measured, not true density. Bulk density is paired with bulkiness (P) and bulkiness with the Helium Pycnometer (R), both mismatched, so this combination is also wrong.
3. (I)-(R), (II)-(S), (III)-(Q), (IV)-(P): True density is the density of the solid material alone, excluding all pores, so it needs a gas like helium that reaches into every void, matching it with the Helium Pycnometer (R). Granule density includes the pores within a particle but not the spaces between particles, and mercury does not penetrate these small internal pores under normal pressure, matching it with the mercury displacement method (S). Bulk density is the mass of powder over the volume it occupies including all the gaps between particles, measured simply by pouring it into a graduated cylinder (Q). Bulkiness is defined as the reciprocal of bulk density (P), the volume taken up per unit mass. Every pairing here matches the standard definition and method.
4. (I)-(S), (II)-(R), (III)-(Q), (IV)-(P): This swaps true density and granule density compared to their correct methods, pairing true density with mercury displacement (S) and granule density with the Helium Pycnometer (R), the reverse of how these are actually measured, so this option is wrong.

Matching each density type to the method that actually measures it, helium pycnometer for true density, mercury displacement for granule density, graduated cylinder for bulk density, and the reciprocal relation for bulkiness, confirms the third combination.

So the correct answer is (I)-(R), (II)-(S), (III)-(Q), (IV)-(P).