Determine Bulk Density of Starch Powder: Formula & Method

APPARATUS REQUIRED:

i) Measuring cylinder

ii) Powder funnel.

iii) weighing balance

CHEMICAL REQUIRED:

Powder sample ( starch soluble powder)

THEORY:

Bulk density refers to the mass of a powder per unit volume, including the void spaces between particles. It is expressed in units such as (g/cm³). In pharmaceuticals, bulk density (ρbulk) is measured to understand the powder’s flow properties, dosage formulation, and packaging efficiency. It is calculated by dividing the mass (M) of the powder by its bulk volume (V bulk).

Ρ bulk = M/V bulk

i) Low bulk density:

Higher porosity can improve flowability due to reduced resistance to particle movement,but excessively low bulk density may lead to poor flow properties due to increased cohesion.

ii) High bulk density:

lower porosity can result in poorer flowability due to increased interparticle friction & cohensian.

In normal limits, the bulk density of powders typically falls within a range of 0.4 to 0.8 g /cm³, but this can vary depending on the specific characteristics of the powder.

PROCEDURE:

The powder whose bulk density is to be determined was passed through sieve no. 20. Then, weighed an empty, dry measuring cylinder and recorded its mass (M₁). Carefully poured the powder sample into the cylinder through a powder funnel unit it filled to a known volume (V). Avoided air entrapment as much as possible leveled the powder surface without compacting it. Weigh the cylinder containing the powder & recorded its mass (M₂) Repeated that process total 3 times and took the average result for better accuracy. Calculate the bulk density using the formula:

Bulk Density = M₂-M₁ / V

OBSERVATION AND CALCULATION:

Wt. of dry measuring cylinder (W₁) = 79.33gm

Wt. of measuring cylinder + Sample (M₂¹) = 115.64.gm

Wt. of measuring cylinder + sample (M₂²) = 116.03 gm

Wt. of measuring cylinder + sample (M₂³) = 115.61gm

Average Wt. (W₃) = M₂¹ + M₂²+ M₂³/3

                           =115.64+ 116.07+115.61/3

                           = 347.28/3

                           =115.76

weight of powder (W₄) = W₃-W₁

                                   = 115.76-79.33

                                   =36.43 gm

Bulk volume of powder (V)= 50 cm³

now,

Bulk density = mass of powder/Bulk volume of powder

                    =W₄/V

                    =36.43/50

                    = 0.73 gm/cm³

RESULT:

The bulk density of starch soluble is found to be 0.73gm/cm³

PRECAUTIONS:

i) Ensure the graduated cylinder is clean, dry & free from any residue before use.

ii) Handle the powder sample carefully to prevent spillage and contamination.

iii) Avoid compacting the powder while filling the cylinder to maintain accuracy.

iv) Use appropriate safety measures when handling powders, such as wearing gloves and a mask if necessary.