Forensic Science Crime Busters Identification Techniques
Crime Busters Forensic Science Identification
Chemical Substance Identification
- Iodine Test: Starch turns blue-black or a dark color (e.g., flour and starch).
- Sodium Chloride (NaCl): Table salt. It dissolves in water, is pH neutral, and forms crystals.
- Sugar: Dissolves in water and does not give the starch iodine reaction.
- Cornstarch: A starch that turns blue-black with iodine; it does not behave like a simple salt or sugar solution.
- Flour: A mixture of substances containing starch (iodine reaction);
Ankit
Atomic absorption spectroscopy (AAS) is a analytical technique used to measure the concentration of specific metallic elements in a sample by detecting the
amount of light they absorb in the gaseous state.
How It Works
Atomization: The liquid or solid sample is vaporized and converted into free ground–
State atoms using a heat source like a flame or graphite furnace.
Light Absorption: A hollow-cathode lamp shines a specific wavelength of light characteristic of the target element through the atomized
Read MoreStates of Matter, Phase Changes, and Atomic Structure
States of Matter Properties
| State | Shape & Volume | Particle Arrangement | Particle Motion | Attractive Forces |
|---|---|---|---|---|
| Solid (s) | Fixed shape and volume | Regular, closely packed lattice | Vibrate about fixed positions | Very strong |
| Liquid (l) | Fixed volume, fits container | Irregular, closely touching | Slide past each other | Moderate |
| Gas (g) | Fills container entirely | Random, far apart | Rapid, random motion | Negligible or weak |
Phase Changes and Transitions
- Melting: Solid to Liquid (thermal energy overcomes strong forces holding particles in fixed
Advanced Methods for Trace Element and Heavy Metal Analysis
Cold Vapor Atomic Absorption Spectroscopy (CV-AAS)
Cold Vapor AAS (CV-AAS) is a specialized atomic absorption technique used only for mercury, because elemental mercury possesses a relatively high vapor pressure at room temperature. First, the mercury present in the sample is converted to Hg2+ using an oxidizing agent such as nitric or sulfuric acid. Then, Hg2+ is reduced to elemental mercury, Hg0, using SnCl2:
Hg2+ → Hg0
Since Hg0 is volatile, it passes into the gas phase and is swept by an inert
Read MoreGlass Electrode Principles and pH Measurement
Understanding the Glass Electrode
The glass electrode is an ion-selective membrane indicator electrode used for pH measurement. In potentiometry, its potential is measured against a reference electrode with a constant and known potential. Therefore, changes in the measured cell potential can be related to changes in the activity of H+ in the analyte solution.
Components of a Glass Electrode
The glass electrode can be used together with a separate reference electrode, or both systems can be incorporated
Read MoreE1 and E2 Elimination Reaction Mechanisms
E₁ & E₂ Reactions
Elimination Reactions
E₁ and E₂ are elimination reactions. These are reactions used in the preparation of alkenes by the dehydrohalogenation of alkyl halides. These reactions involve the removal of a leaving group from a substrate, resulting in the formation of a double bond.
Example:
CH₃–CH₂–Br → CH₂=CH₂ + HBr
There are two types of elimination reactions:
- E₁ reaction
- E₂ reaction
1) E₁ Reaction
E₁ stands for a Unimolecular Elimination reaction. It is unimolecular;
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