Category Archives: Forensic Chemistry

pH

Full form of pH: Potential of Hydrogen or Power of Hydrogen.

pH is a scale that indicates the acidity or basicity of a water-based solutions or other Liquid Solutions.

A solution with a pH below 7 is considered to be acidic; a solution with a pH above 7 is considered to be alkaline.

ph of body Fluids of Human

pH : pH (potential of hydrogen’ or ‘power of hydrogen’) is a scale which is used to specify the acidity or basicity of an aqueous solution.

Human Body need to maintain pH level in the serum about 7.4 to live. pH of blood is 7.4 but the pH of other Body flood is Different. Upper and Lower Part of Stomach have different pH value. Upper stomach pH value ranges from 4.0 to 6.5 while Lower Stomach pH value ranges from 1.5 to 4.0.

Following image has shown the different pH level of Different body fluids of Human Body:

Reference

Worst Stinky Chemicals/Substances on the Earth

We smell many substances / chemicals in our daily lives. Some smell good but some do not. While not all compounds produce odors, several compounds do have recognizable odors, including: Cadaverine and putrescine smell like rotting flesh. Skatole has a strong feces odor. Indole has a mustier, mothball-like smell. Here is a list of similar chemicals that cause the most smell.

☠ World War Weapon-“Who Me?”:

During World War II, the Allied Forces created Who Me – one of the most nefarious chemical weapons. Its was produced to make the target smell like feces.

😷 Ethyl Mercaptan (ethanethiol):

Ethyl Mercaptan smells like leek. 1 part of Ethyl Mercaptan can be detected – without instrumentation – in 2.8 billion parts of air.

The Mirror reads: “The French stench: Gas leak from factory in France causes a stink 200 miles away in UK” and the subheadline reads: “The leak released a colourless gas called mercaptan – listed in the Guinness Book of Records as “the world’s smelliest substance”.

🤢 Butyl seleno-mercaptan (C4H9SeH):

Ethyl mercaptan (C2H5SH) and butyl seleno-mercaptan (C4H9SeH) have an odor reminiscent of a combination of rotting cabbage, garlic, onions, burnt toast and sewer gas. Ethyl mercaptan is added to odorless gas to act as a warning agent.

🤧 Cadaverine :

Cadaverine is decarboxylated lysine that may be isolated from cadavers or pretty much any decaying dead animal. As living flesh decays, amino acids interact and create Cadaverine.

🤯 Skatole:

Skatole or 3-methylindole is an organic compound belonging to the indole family. Occurring in high concentrations, it is the primary odor of feces. But, do you know small amounts of skatole is used to flavor vanilla ice cream. But when it’s not being blended into dairy products, skatole is known for giving human feces part of its odor.

🤮 Butyric Acid:

Butyric acid is a carboxylic acid found in rancid butter, parmesan cheese, and vomit, and has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether). Butyric acid is a fatty acid occurring in the form of esters in animal fats and plant oils.

😤 Dibutyl Telluride:

When you smell “garlic” after tellurium exposure, is (CH3)2Te, or dimethyl telluride. The body metabolizes tellurium the same way it does sulfur, one of the elements that makes garlic stinky.

👾 Pyridine:

It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell which will not go easily. Pyridine is colorless, but older or impure samples can appear yellow. Historically, pyridine was produced from coal tar.

🧟‍♀️ Putrescine:

Putrescine smells like rotting flesh. In fact, the compound at the heart of putrescine is the same as that created by actual rotting flesh.

🥚 Hydrogen selenide:

Hydrogen Selenide smells like rotten eggs mixed with rotten radishes, and poisons you as it “clings” to the insides of your nostrils. It is more toxic than Hydrogen Cyanide, and dulls your sense of smell, making it incredibly dangerous on top of being unpleasantly fragrant.

💨 Mustard Gas:

Mustard Gas (HN3) doesn’t smell like mustard. In reality, Mustard Gas induces fear and hysteria in those unlucky enough to encounter it. Having no antidote, Mustard Gas caused more deaths during World War I than any other chemical weapon despite being less toxic than nerve gas.

🐠 Trimethylamine oxide:

This chemical is found more commonly in ocean sea life and is the reason that cod starts smell faster than river caught catfish. This scent is caused by the breakdown in bacteria combined with the fish enzymes.

💦 Ammonia:

Ammonia is 1 part Nitrogen, 3 parts Hydrogen and all parts repugnant. Some of the more pleasant liquids with traces of ammonia include concentrated cleaning products, cat piss and human sweat.

🙊 Isovaleric Acid:

Isovaleric acid has an identity crisis. On the one hand, the acid gives off at athletic foot smell and makes the body stink of B.O. On the other hand, one of isovaleric acid’s compounds (esters) is used in perfumes due to its fragrant scent. Let’s just hope you catch it on one of its “up” days.

👃Any Thiol:

A thiol is an organic sulfur compound. A familiar example is the rotten egg smell of hydrogen sulfide. Compounds with the S-H group tend to be toxic as well as smelly.

🥡Formaldehyde:

While fly food and disinfected cultures stink, they won’t hurt you. If you can smell formaldehyde, on the other hand, you know you’re poisoning yourself. The chemical, often used as a preservative, has a distinctly unpleasant odor. The nausea and headache are from the toxicity, not just the scent. Paraformaldehyde, a related chemical also used as a fixative, possibly smells even worse.

🍾 n-Butanol:

Trace amounts of fusel alcohols give beer and wine distinctive odors. However, the pure chemical smells vile. n-Butanol is a primary alcohol produced during carbohydrate fermentation. While it’s a solvent in the lab, you’ll also find it as an artificial flavoring in many foods and as a natural chemical in beer, wine, and other fermented products.

🔴 Beta-Mercaptoethanol:

 Beta-mercaptoethanol (2-mercaptoethanol) is used to lower the volatility of chemical solutions and as an antioxidant. The odor is like a cross between rotten eggs and burnt rubber. In high doses, it’s deadly toxic.

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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