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11.4 Notes. High Explosives. Classified into two groups Primary explosives – detonate violently with no burning Used as primers – detonate other explosives via chain reaction Rarely the main ingredient in homemade bombs Secondary explosives – normally burn rather than detonate

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High explosives
High Explosives

  • Classified into two groups

    • Primary explosives – detonate violently with no burning

      • Used as primers – detonate other explosives via chain reaction

      • Rarely the main ingredient in homemade bombs

    • Secondary explosives – normally burn rather than detonate

      • Comprise mostly of commercial and military blasting

      • Dynamite, TNT, PETN, RDX, tetryl


Industrial explosive market
Industrial Explosive Market

  • Moved from nitroglycerin based dynamite to ammonium nitrate based

    • Water gels, emulsions, and ANFO explosives

  • Mix oxygen-rich ammonium nitrate with a fuel to form low-cost, very stable explosive

  • High explosives must be detonated by an initiating explosion such as blasting caps composed of copper or aluminum filled with lead azide


Types of high explosives
Types of High Explosives

  • ANFO is ammonium nitrate soaked in fuel oil

    • Widely used in mining

    • Readily available for homemade varieties due to abundance in fertilizer

  • TATP = triacetone triperoxide

    • Made with acetone, hydrogen peroxide and hydrochloric acid

    • Extremely potent when confined in a pipe

    • Used by terrorists groups in Israel and the Middle East


  • RDX – cyclotrimethylenetrinitramine

    • Most powerful military explosive

    • Often in the form of a plastic doughlike substance called a C-4

  • PETN – Pentaerythritol tetranitrate

    • Used by the military for small-caliber projectiles and grenades

    • Commercial used as a detonating cord

      • Used to interconnect a series of explosive charges so that detonation is simultaneous


Collection and analysis of explosives
Collection and Analysis of Explosives

  • Most important is the collection of samples from the explosion scene

  • Determination of high or low explosive is the presence of a crater at the origin of the blast

  • Locate crater and remove loose soil and debris in the crater to be preserved

    • Wire mesh screens are used for sifting debris

  • Objects near the source must be collected and checked for penetration or residuals on the surfaces


  • Use of the IMS (ion mobility spectrometer)

    • A vacuum to collect explosive residue from surfaces with additional surface residue wiped down with a paper disc

    • The residues are vaporized and converted to electrically charged ions

    • Used as a screening test

  • All materials placed in sealed containers

    • Soil and soft loose materials stored in metal containers or plastic bags


In the lab
In the lab

  • Microscopic examination for particulate recognition

  • Rinse in acetone and analysis with TLC and then GC/MS

    • If it is a low explosive then a rinse in water

  • Confirmation tests include IR Spec; X-ray diffraction


Proposed taggant program
Proposed Taggant program

  • Color coded chips added to commercial explosives

    • Chips are fluorescent and magnetic sensitive

  • Color indicates where the explosive was made and produced

    • Allows for a trace through distribution chain

  • Only now used in Switzerland

    • ICAO (International Civil Aviation Organization) has mandated volatile taggants be added to plastic explosives


11 4 questions
11.4 Questions

  • What is a detonator? What is the composition of most detonators?

  • Name three military high explosives. Which is the most powerful and popular of these explosives?

  • What is the most obvious post-explosion characteristic of a high or contained low explosive?

  • What device is widely used to screen objects for the presence of explosive residues?

  • How are soil and other soft loose materials collected at the scene of an explosion best stored?

  • What is the first procedure typically used to analyze bomb-scene debris that arrives in the laboratory?

  • What does the forensic scientist do to explosive debris following microscopic examination? Why?

  • List three procedures commonly used as screening tests for explosive residues.

  • What is a taggant? What purpose do taggants serve?


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