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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
slide5

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
slide7

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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