2. Gunpowder
● Gunpowder
● Is used or in any of several low-explosive mixtures used
as propelling charges in guns and as blasting agents
in mining.
● The first such explosive was black powder, which
consists of a mixture of saltpeter or
saltpetre (potassium nitrate or nitrate of potash), sulfur,
and charcoal.
● It is prepared in roughly the correct proportions (75
percent saltpetre, 15 percent charcoal, and 10 percent
sulfur).
● Saltpeter when it decomposes at high temperature it can
provide oxygen for the reaction. It is an oxidizer.
● Saltpeter is a chemical compound that is a solid at room
temperature. By itself, it is not explosive, but it can
create a highly explosive, exothermic reaction if in
contact with reducing agents.
3. Gunpowder
• In the investigation of crimes involving the use of firearms, three most important problems may arise.
• The first and primary important one is the problem of determining whether or not a person has fired a gun with bare hands
within a pertinent period of time.
• The second one is the means of determining the probable gunshot range. For example is the distance the firearm held from
the body of the victim at the time of discharge.
• The third is the problem which may come up when the time of the firing of the gun becomes an issue.
• Bullet Trajectory: https://www.youtube.com/watch?v=rvE0aJVVVXU
4. Gunpowder
● Two kinds of Gunpowder:
Black Powder: Possibly the oldest known explosive. It is an explosive mixture of potassium nitrate or sodium
nitrate, charcoal, and sulfur used especially in fireworks and as a propellant in antique firearms
2KNO3 + 3C + S = 3CO2 + K2S + N2
Whereas: S is an oxidizing agent, C is a reducing agent, KNO3 is an oxidizing agent.
Smokeless powder: also known as the gun cotton. It is any of a class of explosive propellants that produce
comparatively little smoke on explosion and consist mostly of gelatinized nitrocellulose (cellulose nitrate) or
Glyceryl nitrate combined with some stabilizers. It can be single or double based propellant.
Stabilizers used are nitrates, bichromates, and oxalates.
Organic stabilizers are nitrobenzene, graphite and Vaseline.
5. Gunpowder
● Possibilities that a person may be found positive for nitrates even if the person did not actually fired a
gun.
It is possible that the gunpowder may have been blown on the hand directly from the barrel of the gun being
fired by another person.
An attempt to shield the body by raising the hand would in some instances result in the implanting of powder
particles on the hand of a person close to one firing a gun.
• Possibilities that a person maybe found negative for nitrates even if he actually fired a gun.
Use of automatic pistols
Direction of the wind
Wind velocity
Excessive precipitation
Use of gloves
Knowledge of chemicals that will remove nitrate trace.
6. Gunpowder and other Explosives
● How to collect, preserve and pack clothing.
Large area as possible surrounding the gunshot hole should be made available for test. If the condition and
appearance of the wound point to a contact shot at all of the clothing in the path of the bullet shout be
collected and be submitted for examination.
Do not roll freely the specimen when doing shipment. Secure the area that to be tested between two layers of
heavy cardboard fastened together tightly to prevent from moving.
Each specimen should be wrapped separately.
Clothing heavily smeared with blood should be dried thoroughly before packing. If the specimen is wet, it may
stick together and may not be suitable for testing anymore.
• How to determine the probable gunshot range.
Singeing
Smudging – blackening of the bullet hole.
Powder tattooing – individual specks of nitrates around the bullet hole visible to the naked eye.
7. Gunpowder
● Chemical Test for Gunpowder Residues.
A method patterned after diphenyl amine test.
Procedure: Coat a piece of clean gauze with a sufficient amount of paraffin to produce a layer of about an .8th
of an inch. Press the layer of paraffin while still warm against the area to be examined.
Walker’s Test – it is a test used if the powder particles are deeply embedded. It is based on the conversion of
nitrates to a dye.
For the modern technology they use the SEM.
8. Gunpowder
● Gunshot Range of Weapons
● Rifle – A weapon on high velocity projectile. Gunshot range is difficult to estimate due to high velocity of the
projectile and the wide variation produced in the wound entrance.
● Shotguns or sporting guns – The projectile is a collection of small shot consisting of the lead pellets that
vary size with types of cartridge.
9. Explosives
● It is an any substance or device that can be made to produce a volume of rapidly expanding gas in an
extremely brief period.
● There are three fundamental types: mechanical, nuclear, and chemical.
● A mechanical explosive is one that depends on a physical reaction, such as overloading a container
with compressed air. Such a device has some application in mining, where the release of gas from chemical
explosives may be undesirable, but otherwise is very little used.
● A nuclear explosive is one in which a sustained nuclear reaction can be made to take place with almost instant
rapidity, releasing large amounts of energy. Experimentation has been carried on with nuclear explosives for
possible petroleum extraction purposes.
● Chemical explosives, which account for virtually all explosive applications in engineering.
10. Explosives
● Classification of Explosives from the viewpoint of Chemical composition.
• Inorganic Compound – example: Lead azide (Pb(N3)2), Ammonium nitrate (NH₄NO₃)
• Organic Compound – example: Trinitrotoluene (TNT: C7H5N3O6), Picric Acid (Trinitrophenol: C6H3N3O7)
Nitrocellulose, Mercury fulminate (Hg(CNO)2)
