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Explosions

Explosions. Explosions. Explosives: substances that undergo a rapid oxidation reaction with the production of large quantities of gases. A sudden buildup of gas pressure determines the nature of the explosion.

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Explosions

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  1. Explosions

  2. Explosions Explosives: substances that undergo a rapid oxidation reaction with the production of large quantities of gases. • A sudden buildup of gas pressure determines the nature of the explosion. • The speed at which explosives decompose permits their classification as high or low explosives. ARSON AND EXPLOSION

  3. Low uses Black or Smokeless powder: • Black powder is a mixture of potassium or sodium nitrate, charcoal, and sulfur. • Smokeless powder consists of nitrated cotton (nitrocellulose) or nitroglycerin and nitrocellulose.

  4. High Explosions Primary and Secondary: • Primary explosives are ultrasensitive to heat, shock, or friction and provide the major ingredients found in blasting caps or primers used to detonate other explosives. • Secondary explosives are relatively insensitive to heat, shock, or friction and will normally burn rather than detonate if ignited in small quantities in the open air. • This group comprises the majority of commercial and military blasting, such as dynamite, TNT, PETN, and RDX. ARSON AND EXPLOSION

  5. The Explosive Market • In recent years, nitroglycerin-based dynamite has all but disappeared from the industrial explosive market and has been replaced by ammonium nitrate-based explosives (i.e., water gels, emulsions, and ANFO explosives). • In many countries outside the United States, the accessibility of military high explosives to terrorist organizations makes them very common constituents of homemade bombs. • RDX is the most popular and powerful of the military explosives, often encountered in the form of pliable plastic known as C-4. ARSON AND EXPLOSION

  6. Collection and Analysis Items collected: • Loose soil from the crater for analysis for chemicals • Foreign items not belonging to the scene • Trace of detonating mechanism • Objects can be screened in the field by the ion mobility spectrometer (IMS). ARSON AND EXPLOSION

  7. Collection and Analysis Collection and Storage: • All materials collected must be placed in sealed air-tight containers. • Debris and articles collected from different areas are to be packaged in separate air-tight containers. • Some explosives can diffuse through plastic and contaminate nearby containers so containers should be glass. ARSON AND EXPLOSION

  8. Back at the Lab • Debris collected at explosion scenes will be examined with a microscope. • Recovered debris may also be thoroughly rinsed with organic solvents and analyzed by • color spot tests • thin-layer chromatography • high-performance liquid chromatography • gas chromatography-mass spectrometry. • Confirmatory identification tests may be performed on unexploded materials by either infrared spectrophotometry or X-ray diffraction. ARSON AND EXPLOSION

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