Stress and Strain help study elasticity, plasticity, and strength of engineering materials. Stress and Strain explain material response—stress is force per area; strains is deformation ratio. Stress (σ) Definition: Stress is the internal force per unit area exerted by a material when an external force is applied. Formula: $\sigma = \frac{F}{A}$ Where: σ = stress … Read more
Purpose of Heckel Equation: The Heckel equation is used to study the compressibility and deformation behavior of powders during tableting. It relates porosity reduction to applied pressure and helps identify whether a material deforms plastically or elastically under compression. Equation: $\ln\!\left(\tfrac{1}{1-D}\right) = KP + A$ Where: D = relative density of the powder (i.e., density … Read more
Elastic and Plastic Deformation explains temporary vs permanent shape changes in materials under stress. Elastic and Plastic Deformation is key in material science for strength, durability, and design. When an external force is applied to a solid, it may change shape or size. This is called deformation. It can be elastic or plastic depending on … Read more
Rotational Viscometer (Brookfield Viscometer) works by measuring torque on a spindle rotating in fluid. Rotational Viscometer (Brookfield Viscometer) measures viscosity of liquids in pharmaceuticals and industries. Principle: 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
Falling Sphere Viscometer (Stoke’s Law Viscometer) is used in labs for accurate fluid viscosity analysis. Falling Sphere Viscometer (Stoke’s Law Viscometer) measures viscosity by tracking a sphere’s fall through liquid. Principle: A ball (usually steel or glass) falls through the test liquid under gravity. The terminal velocity of the ball is used to calculate viscosity, … Read more
Capillary Viscometer (Ostwald Viscometer) measures viscosity by timing liquid flow through a narrow tube. Capillary Viscometer (Ostwald Viscometer) is widely used in labs for comparing fluid viscosities. Principle: Based on Poiseuille’s Law, which describes the laminar flow of liquid through a capillary. Time taken for a fixed volume of liquid to flow between two marks … Read more
Thixotropy in Formulation describes reversible gel-to-sol transitions under shear, improving dosage form handling. Thixotropy In Formulation is a desirable property in liquid pharmaceutical systems, which should have: High consistency in the container. Yet pour or spread easily upon use. Procaine benzyl penicillin (procaine penicillin) combines benzyl penicillin with the local anaesthetic procaine. Thixotropy enhances suspension … Read more
Purine is a bicyclic heterocyclic compound forming the basis of nucleic acids, coenzymes, and many pharmaceutical agents. Structure A fused bicyclic ring: pyrimidine ring fused with imidazole. Molecular formula: C₅H₄N₄ Found in DNA and RNA (adenine and guanine). Synthesis Traube Synthesis Multi-step process starting from 4,5-diaminopyrimidine, formic acid or formamide, then cyclization. Produces purine nucleus. … Read more
Pyrimidine is a six-membered heterocyclic compound with nitrogen atoms, essential in nucleic acids, drugs, and medicinal chemistry. Structure It is a six-membered aromatic heterocycle with two nitrogen atoms at positions 1 and 3. Molecular formula: C₄H₄N₂ Synthesis Biginelli Reaction (for substituted pyrimidines) Reactants: β-keto ester, aldehyde, and urea or thiourea. Conditions: Acidic catalysis, heating. Mechanism: … Read more
Azepines are seven-membered heterocyclic compounds important in medicinal chemistry and drug design for CNS and therapeutic agents. Structure These are seven-membered heterocycles with one nitrogen atom. Can be saturated or unsaturated (aromatic). There are several subclasses: Azepine (basic) Diazepine (2 N atoms – as in benzodiazepines) Thiazepine (N and S atoms) Synthesis of Azepines Ring … Read more
