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11.3 Notes. Explosions. Product of combustion accompanied by creation of gases and heat and occurring at a rapid rate Most bombings are perpetrated by individuals Most bombs are homemade Criminalist must detect and identify the chemicals recovered from the crime scene
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Explosions • Product of combustion accompanied by creation of gases and heat and occurring at a rapid rate • Most bombings are perpetrated by individuals • Most bombs are homemade • Criminalist must detect and identify the chemicals recovered from the crime scene • Identify the detonating device
Gas pressures expand and compress layers of surrounding air moving out in all directions • Causes violent physical disruption of surrounding environment • Can create artificial gale as high as 7000 miles per hour • May be classified as a high explosion or a low explosion
Speed of deflagration • Burning • Characterized by rapid oxidation that produces heat, light, and subsonic pressure waves • Low Explosives • Include Black and smokeless powders
Speed of denotation • Creation of a supersonic shock wave within the explosive charge • Shock wave causes the chemical bonds of the explosive charge to break apart, leading to new instantaneous buildup of heat and gas • High explosives • Include dynamite, TNT, PETN, RDX • Detonate almost instantaneously at 1,000 to 8,500 m/s
Low Explosives • Used as a medium to carry a flame • Only ingredients required = fuel and oxidizing agent • Oxidizing agent = Potassium chlorate KClO3 • When mixed with sugar produces a popular and accessible explosive mix • Chlorate can also be combined with carbon, sulfur, starch, phosphorus and magnesium • Suitable as propellants for ammunition or skyrockets but dangerous
Black Powder • Stable mix of KNO3/NaNO3, charcoal and sulfur • Unconfined if just burns • Used as a medium for carrying a flame • Safety Fuse – black powder wrapped in fabric or plastic casting • Becomes explosive and lethal when contained
Smokeless powder • Safest and most powerful • Consists of nitrated cotton, single-base powder, or double-base powder Natural Gas • Escapes from confided area and mixes with sufficient amount of air • Simultaneous combustion • Will only explode or burn in limited concentration range (5.3-13.9%) • Too high = not enough oxygen for combustion • Too low = not concentrated enough for combustion
11.3 Questions • What produces the violent physical disruption associated with an explosion? • What is the difference between deflagration and detonation? • What ingredients are required to create a low explosive? • What types of explosives largely have replaced dynamite for industrial uses? What are the advantages of these types of explosives? • What is a detonator? What is the composition of most detonators?