February 23, 2024

Determination of bulk density, true density and porosity

Determination of bulk density, true density and porosity

BP407P Physical Pharmaceutics II Practical


To determine the bulk density, true density, and percentage porosity of the given granules


• When particles are packed loosely lots of gaps between the particles are
observed. Hence the bulk volume increases by making the powder light based on bulk volume powder are classified as light and heavy
• light powder has high bulk volumes on the other hand smaller particles the powder assume low bulk volume or high bulk volume density such powder is called heavy powder. The bulk density depends on particle size distribution, shape, and cohesiveness of particles.
• True density is the density of the powder itself True density= ⁄
• The density depends on the type of atom in a molecular rearrangement of atoms in a molecule and arrangement of molecule in the sample volume occupied by voids and the intra-particle pores are not included in the most common method used in the determination of true density or gas displacement or liquid displacement method.
• This method is used to select a solvent in which the powder is insoluble


Approximately 20gm of powder is transformed into a 500ml cylinder and tapped mechanically or by tapping device until a constant volume is obtained thus volume is bulk volume and the void space among powder particle

True density:

Determination of true density of the material by solvent displacement method

  • Weigh accurately a clean and dry density bottle
  • Take the weight of the density bottle with a small quantity of powder sample
  • Now fill the density bottle with solvent without removing the powder material
  • Calculate the true density of the given powder sample

Determination of percentage porosity

Porosity is defined as the void volume to the bulk volume of the granules
Porosity=1- ⁄


  • The bulk density of the given sample of granules was found to be = g/cm3
  • The true density of a given powder was found to be = g/cm3
  • The percentage porosity of the given powder is = %

True Density and Bulk Density: Understanding the Difference

True Density and Bulk Density: Understanding the Difference

Density is a fundamental property of matter that quantifies how much mass is contained within a given volume. In the context of materials and substances, two important density measurements are often discussed: true density and bulk density. While both measurements provide insights into the physical characteristics of materials, they focus on different aspects and are used for distinct purposes. Let’s explore the differences between true density and bulk density:

True Density:

Definition: True density, also known as real density or absolute density, refers to the mass of a substance per unit volume, excluding any voids or pores within the material.

Calculation: True Density (ρ) = Mass (m) / Volume (V)

Significance: True density provides a measure of the intrinsic density of a material, disregarding any interstitial spaces or porosity. It reflects how tightly the atoms or molecules are packed within the material’s structure.

Application: True density is often used in scientific research, materials science, and quality control. It is especially valuable when analyzing pure, solid materials, nanoparticles, and powders where porosity is negligible.

Bulk Density:

Definition: Bulk density refers to the mass of a material divided by the total volume it occupies, including the spaces between particles or aggregates.

Calculation: Bulk Density (ρ_bulk) = Mass (m) / Total Volume (V_total)

Significance: Bulk density takes into account the presence of voids, pores, or spaces between particles within a material. It is a measure of how densely or compactly the material is packed in a container.

Application: Bulk density is commonly used in industries like agriculture, construction, and pharmaceuticals. It helps determine the storage, transportation, and handling characteristics of granular or particulate materials, such as powders, grains, or aggregates.

Key Differences:

  1. Focus of Measurement:
  • True density focuses on the intrinsic density of a material, excluding any voids or pores.
  • Bulk density considers the overall density of a material, accounting for the presence of voids and interstitial spaces.
  1. Measurement Context:
  • True density is used for analyzing the fundamental atomic or molecular packing of a substance, especially in research and materials science.
  • Bulk density is employed in practical applications like material handling, storage, and transport, where voids and particle arrangement affect properties.
  1. Materials Analyzed:
  • True density is suitable for homogeneous, solid materials with minimal porosity, such as pure metals or solid ceramics.
  • Bulk density is applicable to heterogeneous or granular materials, including powders, grains, or aggregates.
  1. Influence of Porosity:
  • True density disregards porosity and provides insight into the ideal packing arrangement of particles.
  • Bulk density considers porosity and reflects the overall arrangement and compaction of particles.

In summary, true density and bulk density are distinct measurements used to characterize different aspects of material properties. True density delves into the fundamental atomic/molecular arrangement, while bulk density addresses practical considerations related to particle packing and material handling. Understanding the differences between these density measurements is essential when interpreting data and applying them to various fields of science and industry.

Physical Pharmaceutics II Practical

  1. Determination of particle size, and particle size distribution using the sieving method
  2. Determination of particle size, and particle size distribution using the Microscopic method
  3. Determination of bulk density, true density and porosity
  4. Determine the angle of repose and the influence of lubricant on the angle of repose
  5. Determination of viscosity of liquid using Ostwald’s viscometer
  6. Determination of sedimentation volume with the effect of different suspending agent
  7. Determination of sedimentation volume with the effect of different concentrations of single suspending agent
  8. Determination of viscosity of semisolid by using Brookfield viscometer
  9. Determination of reaction rate constant first order.
  10. Determination of reaction rate constant second order
  11. Accelerated stability studies

Frequently Asked Questions (FAQs)

True density is a fundamental concept in pharmaceuticals that plays a significant role in the formulation, manufacturing, and quality control of pharmaceutical products. Here are some frequently asked questions to help you understand true density in the context of the pharmaceutical industry:

What is true density in pharmaceuticals?

True density, also known as real density, is a measure of the mass of a substance per unit volume, excluding any voids or pores. It reflects the compactness of the material without considering the presence of any air or gaps.

Why is true density important in the pharmaceutical industry?

True density is crucial in pharmaceuticals for various reasons, including:
Determining the packing and compressibility behavior of powders used in tablet formulations.
Assessing the efficiency of drug delivery systems, such as inhalers and nasal sprays.
Controlling the quality of active pharmaceutical ingredients (APIs) and excipients.
Optimizing granulation and compaction processes during tablet manufacturing.

How is true density measured?

True density is typically measured using techniques such as helium pycnometry or gas displacement. In a helium pycnometer, a sample is immersed in a chamber filled with helium gas, and the volume displaced by the sample is used to calculate true density.

How does true density differ from bulk density?

Bulk density includes the volume occupied by the material and its pores, voids, or inter particulate spaces. True density, on the other hand, only considers the volume of the solid material itself, excluding any voids.

What factors can affect the true density of pharmaceutical materials?

True density can be influenced by factors such as the molecular structure of the material, particle size distribution, crystallinity, porosity, and the presence of any solvents or additives.

How is true density relevant to tablet formulation?

True density plays a role in tablet formulation as it affects the compaction behavior of powders. Powders with higher true density tend to be less compressible, requiring higher compression forces during tablet manufacturing.

Can true density impact drug release?

Yes, true density can influence drug release rates from solid dosage forms. Higher true density can lead to slower dissolution rates, affecting the drug’s bioavailability and therapeutic effectiveness.

What is the relationship between the true density and flow properties of powders?

The flow properties of powders, such as their ability to flow smoothly during processing, can be influenced by true density. Materials with higher true density often exhibit improved flowability.

How is true density used in the development of inhalation products?

In inhalation products like dry powder inhalers, understanding the true density of drug particles is crucial for achieving accurate dosing and effective aerosolization during inhalation.

How is true density utilized in the development of granules and pellets?

In the development of granules and pellets, knowledge of the true density helps in optimizing formulation parameters, such as the selection of excipients and the determination of appropriate compaction forces.

Can true density assist in detecting counterfeit drugs?

True density measurements can be used as part of a multi-parameter approach to assess the authenticity of pharmaceutical products and detect counterfeit drugs.

How can variations in true density impact tablet uniformity?

Variations in true density among different batches of excipients or APIs can lead to inconsistencies in tablet weight and composition, affecting tablet uniformity and drug content.

Is true density used in the quality control of pharmaceuticals?

Yes, true density is employed in quality control to ensure the consistency and integrity of pharmaceutical materials and products. It helps verify the identity and quality of raw materials and finished dosage forms.

Can true density influence the stability of pharmaceutical formulations?

Yes, true density can affect the stability of pharmaceutical formulations, as it can impact the interactions between different components of the formulation, such as APIs and excipients.

How is true density information used in regulatory submissions?

True density data may be included in regulatory submissions to provide comprehensive information about the physical properties of pharmaceutical materials, aiding in the evaluation of safety and efficacy.

Understanding true density and its implications in pharmaceuticals is essential for developing safe, effective, and high-quality pharmaceutical products. It is a critical parameter that influences various stages of drug development, manufacturing, and quality control processes.

Second Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise

S Y B Pharm Sem IIIS Y B Pharm Sem IV
BP301T Pharmaceutical Organic Chemistry II TheoryBP401T Pharmaceutical Organic Chemistry III Theory
BP302T Physical Pharmaceutics I TheoryBP402T Medicinal Chemistry I Theory
BP303T Pharmaceutical Microbiology TheoBP403T Physical Pharmaceutics II Theory
BP304T Pharmaceutical Engineering TheoryBP404T Pharmacology I Theory
BP305P Pharmaceutical Organic Chemistry II PracticalBP405T Pharmacognosy I Theory
BP306P Physical Pharmaceutics I PracticalBP406P Medicinal Chemistry I Practical
BP307P Pharmaceutical Microbiology PracticalBP407P Physical Pharmaceutics II Practical
BP308P Pharmaceutical Engineering PracticalBP408P Pharmacology I Practical
BP409P Pharmacognosy I Practical

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