1. 11.4 Notes

2. 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

3. 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

4. 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

5. Industrial Explosive Market
Moved from nitroglycerin based dynamite to ammonium nitrate based
Mix oxygen-rich ammonium nitrate with a fuel to form low-cost, very stable explosive
High explosives must be detonated by an initiating explosion

6. Detonator Most common type is a blasting cap
Composed of copper or aluminum cases filled with lead azide as an initiating charge and PETN or RDX as a detonating charge
Homemade bombs usually initiated by an electrical blasting cap

7. 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

8. 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

9. 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

10. 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. 11.4 Questions
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?