Evolution of Atomic Models: From Democritus to Quantum Mechanics
First Atomic Models
Democritus (450 BC)
Proposed the idea of atoms as indivisible particles.
Dalton Atomic Model
Introduced atomic-molecular theory:
- Matter consists of indivisible atoms.
- Atoms of the same element have identical mass and properties.
- Compounds form from combinations of different elements.
- Mass is conserved in chemical reactions.
- Law of multiple proportions.
Lavoisier: Law of Conservation of Mass
Proust: Law of Definite Proportions
Atomic Model – Thomson
Discovered electrons through cathode ray
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Liquid Mixing vs. Solid Mixing
Liquid Mixing
- Generally involves liquid-liquid or liquid-gas mixing.
- Depends on flow currents for material transport.
- Requires less power.
- Results in a homogenous liquid phase.
- Well-mixed samples are homogenous.
- Equipment: Liquid agitators.
- Technology is well-understood and simple.
Solid Mixing
- Resembles low-viscosity liquid mixing to some extent.
- Lacks flow currents in heavy masses; mixing occurs differently.
- Requires higher power.
- Product may have identifiable phases.
- Well-mixed
Atomic Structure: From Dalton to Quantum Theory
Structure of the Atom
In 1808, English chemist J. Dalton formulated his atomic theory, postulating that matter consists of indivisible atoms. This concept prevailed until the discovery of natural radioactivity by Henri A. Becquerel in 1896, revealing alpha, beta, and gamma rays, suggesting atoms were divisible.
The Electron: Plum Pudding Model
Studies on gas conductivity at low pressure revealed cathode rays, streams of negatively charged particles. J.J. Thomson identified these as electrons. In 1911,
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Chemical Bonding
Chemical bonding is the joining of atoms, molecules, or ions to create larger structures. These molecules can further interact through intermolecular forces to form more complex, multimolecular structures.
Types of Chemical Bonds
- Ionic Bond: Occurs due to electrical forces between oppositely charged ions, forming an ionic crystal.
- Covalent Bond: Forms when atoms share a pair of electrons, typically completing their valence shells.
- Metallic Bond: Results from the electrical attraction
Pharmaceutical Analysis: Methods and Quality Control
Milk of Magnesia (Magnesium Hydroxide)
This alkalinization is based on a neutralization between milk of magnesia, which is magnesium hydroxide, and auxiliary substances such as stabilizers, preservatives, and viscosity agents like carboxyl methyl cellulose.
Used as an indicator (heliantina 3.1 to 4.4)
Reference value: 7.5 – 8.5 g% Mg(OH)2
Saline Analysis (Argentometric)
The Volhard method for residual valuation is commonly used and involves two determinations:
Direct determination: Silver salts
Residual
Industrial Safety Essentials: Hazards and Prevention
Safety in Gas-Welding (Cutting)
Gas welding uses flammable gases like acetylene and oxygen. Acetylene can ignite and condense, while oxygen accelerates burning. Wear eye goggles, flameproof aprons, gloves, caps or helmets, and boots. Ensure clothing is free from oil or grease.
Environmental Safety
Ensure proper ventilation, lighting, walkways, storage, escape routes, and safety posters. Keep floors clean and dry. Fire extinguishers should be accessible, and welded jobs stored properly.
Operation and
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