Introduction of Surface and Interfacial Phenomena Surface and Interfacial Phenomena are critical in pharmaceutical sciences as they impact the formulation, stability, and effectiveness of dosage forms like emulsions, suspensions, foams, and ointments. These phenomena describe the interactions at the boundaries (interfaces) between different phases of matter—solid, liquid, and gas. A thorough understanding of these interactions … Read more
Definition of Dissociation Constant: It is a measure of the extent to which a compound separates into its components in solution. For a general reaction: $\text{AB} \leftrightarrow \text{A} + \text{B}$ the dissociation constant is given by :$K_d = \frac{[A][B]}{[AB]}$ Properties of Dissociation Constant: Equilibrium: Indicates the position of equilibrium for dissociation reactions. Strength of Interaction: … Read more
Definition of Dipole Moment: It is a measure of the separation of positive and negative charges in a molecule. It is given by: $\mu = q \cdot d$ where q is the charge and d is the distance between the charges. Measured in Debye units (D), the dipole moments indicate the polarity of a molecule. … Read more
Definition: Dielectric Constant is a measure of a material’s ability to store electrical energy in an electric field. It is the ratio of the permittivity of the material (ε) to the permittivity of free space (ε0) $\kappa = \frac{\varepsilon}{\varepsilon_0}$ Properties: Capacitance: The dielectric constant affects the capacitance of a capacitor, given by: $C = \kappa … Read more
Definition of Optical Rotation Optical Rotations refers to the rotations of the plane of polarization of polarized light as it passes through an optically active substance. It is quantified as $\alpha = [\alpha] \cdot l \cdot c$ where: α is the observed rotation (degrees). [α] is the specific rotation (degrees·dm⁻¹·g⁻¹·mL). l is the path length … Read more
Definition of Refractive Index: it is the index (n) is a measure of how much light is bent, or refracted, when it enters a substance. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the material: $n = \frac{c}{v}$ where: c is the speed of … Read more
Polymorphism is the ability of a material to exist in more than one crystal structure. Characteristics of Polymorphism: Multiple Structures: A single chemical compound can form different crystalline arrangements, each with distinct properties. Phase Transitions: Polymorphs can transform from one form to another under certain conditions such as temperature and pressure changes. Types of Polymorphs: … Read more
Solid – Amorphous lack a long-range ordered structure. Characteristics of Solid – Amorphous: Short-Range Order: Atoms are ordered only over short distances. Isotropy: Properties are generally uniform in all directions. Broad Melting Range: Gradually soften over a range of temperatures rather than having a sharp melting point. Formation of Solid – Amorphous: Rapid cooling of … Read more
Solid – Crystalline have a well-defined, repeating atomic structure extending in all three spatial dimensions. Characteristics of Solid – Crystalline: Long-Range Order: Atoms or molecules are arranged in a repeating pattern. Anisotropy: Physical properties depend on the direction due to the ordered structure. Sharp Melting Point: Crystalline solids melt at a specific temperature. Types of … Read more
Glassy States refer to the amorphous state of a material where it behaves like a solid but has a disordered atomic structure like a liquid. Characteristics of Glassy States: Non-crystalline: Lacks long-range order typical of crystals. Transition: Forms when a liquid is cooled rapidly, bypassing the crystalline state, resulting in a solid without a defined … Read more
