Tag Archives: explosive

Forensic Chemistry (Introductory)

Question- What is Chemistry?

Answer- Chemistry is an integral part of Science.

Question- What is Forensic Chemistry?

Answer- Forensic Chemistry applies Chemical Principles and it’s Concept to analyze physical or biological evidences to assist Law and Criminal Justice.

Question- What is Forensic Chemist?

Answer- Forensic Chemists performs different test and methods to identify and analyze different types of evidences to assist legal justice system.

Question- What are the areas of forensic chemistry in forensic science?

Answer- Areas of Applications of Forensic Chemistry

  • Explosives and Gun Shot Residue (GSR)
  • Inorganic and organic Analysis
  • Drugs and Toxic Substances
  • Petroleum
  • Alcohols
  • Biological samples
  • Deoxyribonucleic Acid
  • Fingerprints
  • Documents, Etc.

Question- What is the Scope & Significance of Forensic Chemistry ?

Answer- there are lots of Scope & Significance of Forensic Chemistry in legal &judiciary system. Some of these are given below:

  • Analysis of dyes, paints, inks, fillers, Binders and various other chemicals.
  • Adulteration in building materials, such as; cement, bricks, sand, rods, etc.
  • Examination of metal alloys and metal fragments.
  • Analysis of Drugs or Narcotic Drugs.
  • Analysis and examination of  Pesticides & Insecticides.
  • Analysis of Explosive, Firearms & Ammunition.
  • Determination of Alcohol in body fluids(Blood, Urine).
  • Examination of petroleum products, inflammable material
  • Analysis of Forgery in Suspected Document, such as ; ink, paper, binders, etc.

Question- How Forensic Chemists Examine Exhibits/Samples?

Answer- Exhibits/Samples are examine in various steps by forensic chemists, which are;

  • When question samples are submitted for analysis the first task of examiner is to identify the sample by sensory tests, simple physical and chemical methods so they can differentiate the sample and categorize it.
  • Then Suspected Composition Is Confirmed By suitable Confirmatory Test which will be done to confirm the particular substance.
  • After That It Will Be Confirm By Specific Chemical Techniques Or Instruments.

Question- What chemical techniques do Forensic Chemists use?

Answer- Various Instruments are used for Specific micro-chemical analysis by which the evidences are properly examined and elucidate, such as;

  • Gas Chromatography (GC)
  • UV-IR Spectrophotometers
  • Fourier Transform InfraRed Spectrometer (FT-IR)
  • Liquid Chromatography (LC)
  • Gas-Liquid Chromatography (GLC)
  • High-Performance Liquid Chromatography (HPLC)
  • Gas Chromatography-Mass Spectrometry (GC-MC)
  • Liquid Chromatography-Mass Spectrometry (LC-MC)
  • Nuclear Magnetic Resonance Spectroscopy (NMR)
  • Neutron Activation Analysis (NAA), etc.

Explosive

By @forensicfield

What are Explosives?

Explosives are chemical compounds or mixture of compounds which are suitably initiated by heat, shock, friction or ignition will undergo a rapid chemical decomposition.

Explosion occurs with the evolution of heat, flash, loud sound and explosion of gases producing blast.

Types of Explosion

Normally There Are Three Types Of Explosives :

  • Nuclear
  • Chemical
  • Mechanical

Nuclear Explosive

A nuclear explosive is an explosive device that derives its energy from nuclear reaction.

Almost all nuclear explosive devices that have been designed and produced are nuclear weapons intended for warfare.

Nuclear Explosive Are Of Two Types:

  • Fission – Splitting of nucleus of atoms.
  • Fusion – Joining together under great force the nuclei of atoms.

Mechanical Explosive

A mechanical explosive is one that depends on a physical reaction, such as overloading a container with compressed air.

Chemical Explosive

A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat.

Categories Of Explosives

Explosives are classified as LOW  or HIGH explosives according to their rates of burn.

Low Explosive

Low Explosive Is usually a mixture of a combustible substance and an oxidant that decomposes rapidly however they burn slower than a high explosive which has an extremely fast burn rate as opposed to most high explosives which are compound.

Normally, low explosives undergo deflagration at rates that vary from a few cm/sec to approx 400 m/sec.

Low explosive are normally used as a propellants. Such as gun powder , flares and illumination devices.

High Explosives

High explosive compounds detonates at rates ranging from 3, 000 to 9,000 meters/sec.

High explosives are subdivide into two classes on the basis of sensitivity :-

Primary Explosives

Primary Explosives are extremely sensitive to mechanical shock, friction an heat to which they will respond by burning rapidly or detonating.

ex- mercury fulminate, lead styphnate and lead azide.

Secondary Explosive

Secondary Explosive also known as base explosives. These types of explosive are extremely sensitive to shock, friction and heat.

They may burn when exposed to heat or flame in small, unconfined quantities, but detonation can occur.

Dynamite, TNT, RDX, PETN, HMX and others are examples of secondary explosives.

Composition of an Explosive

It may be composed of chemically pure compound. Such as nitroglycerine.

It may be mixture of oxidizer and a fuel, such as black powder.

-: Mixture Of An Oxidizer And A Fuel :-

  1. Black Powder – Potassium Nitrate(75%) + Charcoal (15%) + Sulphur(10%)
  2. Flash Powder – Fine Metal Powder (Usually Mg Or Aluminum). + Strong Oxidizer (Potassium Chlorate Or Perchlorate)
  3. Ammonal – Ammonium Nitrate + Aluminum Powder.
  4. Armstrong’s Mixture – Potassium Chlorate + Red Phosphorus (Sensitive Mix.) (Primary High Explosive).
  5. Sprengel Explosives– Strong Oxidizer + High Reactive Fuel (Chlorates + Nitroaromatics)

Chemically Pure Compound

  • Nitroglycerine – A highly unstable and sensitive liquid.
  • Acetone Peroxide – White Unstable Organic Peroxide.
  • TNT – Yellow Insensitive crystals
  • Nitrocellulose – A nitrated Polymer.
  • RDX, PETN, HMX – Very powerful explosives (used in pure or in plastic explosive).
  • C-4 – RDX Plastic Explosive.

What Is Chemical Explosive Reaction?

  • A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat.
  • For a chemical to be an explosive, it must exhibit all of the following:
  • Rapid expansion (rapid production of gases or rapid heating of surroundings)
  • Evolution of heat
  • Rapidity of reaction
  • Initiation of reaction.

Evolution Of Heat

The generation of heat in large quantities accompanies every explosive chemical reaction. Rapid liberation of heat that causes the gaseous products of reaction to expand and generate high pressures.  This rapid generation of high pressures of the released gas constitutes the explosion.

Rapidity Of Reaction

Rapidity of reaction distinguishes the explosive reaction from an ordinary combustion reaction by the great speed with which it takes place.

Initiation of Reaction

This reaction occurred after being initiated by the application of shock or heat to a small portion of the mass of the explosive material.

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