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Definition of Emulsions: An emulsion is a biphasic (two-phase) system consisting of two immiscible liquids, where one liquid (the dispersed phase) is finely dispersed in the form of droplets throughout the other (the continuous phase), stabilized by an emulsifying agent. Classification of Emulsions Emulsions can be classified into four types: Oil-in-Water (O/W) Emulsion: Oil droplets … Read more
Deflocculated Suspensions show slow sedimentation but form a hard cake, making redispersion difficult. Deflocculated Suspensions Particles remain separate and discrete. Settle slowly due to small size and mutual repulsion. Can lead to caking—a dense sediment forms that’s hard to redisperse. Advantages of Deflocculated Suspensions: Appears more uniform Slower settling Disadvantages of Deflocculated Suspensions: Risk of … Read more
Flocculated Suspensions are agents (like electrolytes, polymers) are used. Flocculated Suspensions Particles form loosely bound clusters called flocs. Flocs are light and settle rapidly but form a loose sediment that is easily redispersed. Zeta potential is reduced (but not too low) to promote controlled aggregation. Advantages: No caking Easy redispersion Uniform dose upon shaking Disadvantages: … Read more
Settling in Suspensions affects stability, dosage uniformity, and quality of pharmaceutical formulations. Settling In Suspensions is a natural consequence in suspensions due to gravity acting on particles denser than the liquid. Stokes’ Law The rate of settling V of spherical particles in a fluid is described by: $V = \frac{2 r^{2} (\rho_{p} – \rho_{f}) g}{9 … Read more
Rotational Viscometer (Brookfield Viscometer) measures fluid viscosity by spindle rotation resistance. It is widely used in pharma, food, and cosmetic industries. Principle of Rotational Viscometer (Brookfield Viscometer): Measures the torque required to rotate a spindle at constant speed in the sample. The resistance to rotation is a function of the sample’s viscosity. $\eta \propto \frac{\text{Torque}}{\text{Angular … Read more
Optical Properties of Colloids help in particle size analysis and stability studies of colloidal systems. Optical Properties of Colloids explain light scattering, Tyndall effect, and visibility of dispersed particles. Colloidal particles, due to their size (1–1000 nm), interact with light in unique ways. These optical effects help characterize and analyze colloidal systems. Tyndall Effect Definition: … Read more
Claisen-Schmidt Condensation forms α,β-unsaturated carbonyl compounds by reacting aromatic aldehydes with ketones in base. The Claisen–Schmidt condensation is a base-catalyzed aldol condensation between an aromatic aldehyde and a ketone (or sometimes another aldehyde) with α-hydrogens, typically resulting in an α,β-unsaturated carbonyl compound. General Reaction: Aromatic aldehyde + Aliphatic ketone —(Base/heat) → α,β-unsaturated ketone + H₂O … Read more
Schmidt Rearrangement converts carboxylic acids, ketones, or aldehydes into amines and amides using hydrazoic acid. The Schmidt rearrangement is a chemical reaction involving the reaction of hydrazoic acid (HN₃) with carbonyl compounds (like carboxylic acids, ketones, or aldehydes) in the presence of acid to yield amines, amides, or nitriles, depending on the substrate. Overview of … Read more
Beckmann Rearrangement converts oximes into amides or lactams under acidic conditions, important in drug and polymer synthesis. Overview of Beckmann Rearrangement: The Beckmann rearrangement converts oximes into amides via acid-catalyzed rearrangement. Generally used for converting ketoximes into N-substituted amides. If starting from aldoximes, the product is a primary amide. General Reaction: R1–C=NOH–R2 → R1–CONH–R2 (in … Read more
Dakin Reaction converts ortho- and para-hydroxy aromatic aldehydes or ketones to dihydroxybenzenes using hydrogen peroxide. Overview of Dakin Reaction: The Dakin reaction involves the oxidation of aryl aldehydes or aryl ketones, especially those with electron-donating groups (–OH or –OR) in the ortho or para position, to phenols using hydrogen peroxide in basic medium. Reagents: Hydrogen … Read more
