1. 14-1 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Warm-Up: December 3, 2014 How can fire debris help determine if a fire was caused by arson?

2. 14-2 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Objective SWBAT understand how explosives are classified.

3. 14-3 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Agenda 1.Follow the Case 4 & 5 2.OKC Bombing Documentary 3.Explosives 4.High vs. Low Explosives 5.Follow the Case 6.Exit Slip

4. 14-4 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Follow that Case http://www.interfire.org/features/followTha tCase/episode001.asphttp://www.interfire.org/features/followTha tCase/episode001.asp

5. 14-5 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein OKC Bombing Documentary 16. Who was McVey and Nicholls receiving funds from? 17. What do federal prosecutors believe caused the confusion of John Doe 2? 18. What was the most powerful piece of evidence? 19. What was McVey’s supposed motive?

6. 14-6 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Explosions A chemical explosive is a compound or a mixture of compounds which, when subjected to heat, impact, friction, or shock, undergoes very rapid, self-propagating, heat- producing decomposition.

7. 14-7 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Explosions

8. Introduction to Explosives Most bombing incidents involve homemade explosive devicesMost bombing incidents involve homemade explosive devices There are a great many types of explosives and explosive devicesThere are a great many types of explosives and explosive devices Lab must determine type of explosives and, if possible, reconstruct the explosive deviceLab must determine type of explosives and, if possible, reconstruct the explosive device

9. Explosives An explosive is a material that undergoes rapid exothermic oxidation reaction (combustion), producing immense quantities of gas.An explosive is a material that undergoes rapid exothermic oxidation reaction (combustion), producing immense quantities of gas. The build-up of gas pressure in a confined space is the actual “Explosion”. The damage is caused by rapidly escaping gases and confinement.The build-up of gas pressure in a confined space is the actual “Explosion”. The damage is caused by rapidly escaping gases and confinement. The ignition of an explosive is called DetonationThe ignition of an explosive is called Detonation

10. Explosives Combustion (or decomposition) of explosives occurs so rapidly, that there isn’t enough time for the oxygen in the surrounding atmosphere to combine with the fuel. Therefore, many explosives must have their own source of oxygen – or oxidizing agents

11. 14-11 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Shock Wave It is this sudden buildup of gas pressure that constitutes the nature of an explosion. The speed at which explosives decompose permits their classification as high or low explosives. Video: Rocket fuel production plant shock wave. http://www.youtube.com/watch?v=_KuGizBjDXo http://www.youtube.com/watch?v=_KuGizBjDXo

12. Types of Explosives Low explosives Combustion is relatively slow -1000 meters per second speed of deflagrationThe speed of explosion is called the speed of deflagration Crucial element is physical mixture of oxygen and fuel Examples are black and smokeless powders Black powder is mixture of potassium nitrate, charcoal and sulphur Smokeless powder is nitrocellulose and perhaps nitro- glycerine

13. Black Powder (Low Explosive) Black powder contains: –75% Potassium Nitrate (KNO 3 ) –15% Charcoal (C) –10% Sulfur (S) The KNO 3 is the oxidizing agent. –When heat is applied to the powder, the oxygen from KNO 3 is liberated. –It combines with the carbon (fuel) and sulfur (for stable combustion). –The combustion of charcoal and sulfur produces 2 gases – CO 2 and N 2. –The buildup of gases in the cartridge, propels the bullet forward in bullet cartridges.

14. Black Powder Reaction 3C + S + 2KNO 3  3CO 2 + N 2 + K 2 S + heat Carbon in charcoal is fuel Sulfur stabilizes combustion Saltpeter is the oxidizing agent Carbon dioxide gas Nitrogen gasPotassium Sulfide solid

15. Smokeless Powder Used as propellant in firearms and other weapons. There are 3 types: –Single-base – contains nitrocellulose –Double-base – contains nitrocellulose and nitroglycerine –Triple-base – contains nitrocellulose, nitroglycerine and nitroguanidine Produce very little smoke when burned, unlike black powder. The reason that they are smokeless is that the combustion products are mainly gaseous, compared to around 55% solid products for black powder (potassium carbonate, potassium sulfate residues).

16. 14-16 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Gunpowder The most widely used explosives in the low- explosive group are black powder and smokeless powder. Burn rate is less than 3000 ft/second Black powder is a mixture of potassium or sodium nitrate, charcoal, and sulfur. VideoVideo Smokeless powder consists of nitrated cotton (nitrocellulose) or nitroglycerin and nitrocellulose. VideoVideo

17. Types of Explosives part deux High explosives – they detonate (explode) rather than deflagrate (burn) Combustion can range from 1000 mps to 10,000 mps Oxygen usually contained in fuel molecule Two types  Initiating (or primary explosives) Sensitive, will detonate readily when subjected to heat or shock. Used to detonate other explosives in explosive train (a triggering sequence that ends up in a detonation of explosives) Includes Nitroglycerine  Noninitiating (Secondary or base explosives) relatively insensitive, to heat, friction or shock, need special detonators such as low explosives. Includes Dynamite, TNT or PETN ANFOs or (Ammonium Nitrate Fuel Oil) (These are actually tertiary)

18. 14-18 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Explosions Among the high explosives, primary explosives are ultra-sensitive to heat, shock, or friction and provide the major ingredients found in blasting caps or primers used to detonate other explosives. Examples are DDNP and lead azide. Web siteWeb site Burn rates are 3000 –9000 ft/second. Blasting Caps

19. 14-19 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein DDNP DDNP, an acronym for diazodinitrophenol, is a picric acid derivative with somewhat good stability and explosive velocity. It is still susceptible to heat, friction, and shock making it a primary explosive. Its preparation is very simple, needing only picramic acid, sodium or potassium nitrite, and some dilute hydrochloric or sulfuric acid. This compound was first prepared by Dr. Griess in 1858, and this led him to conduct ground breaking research on the diazotization reaction.

20. 14-20 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary 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. Dynamite & TNT, PETN, RDX Diagram of dynamite. 1.Sawdust soaked in nitroglycerin. 2.Protective coating surrounding the explosive material. 3.Blasting cap. 4.Electrical cable (or fuse) connected to the blasting cap.

21. 14-21 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Dynamite Dynamite is an explosive material based on nitroglycern, initially using diatomaceous earth or another absorbent substance such as powdered shells, clay, sawdust, or wood pulp. Dynamite was invented by the Swedish chemist Alfred Nobel 1867. Remember Nobel Prizes? Dynamite is usually sold in the form of sticks about 8 in (20 cm) long and about 1.25 in (3.2 cm) in diameter, with a weight of about 0.5 lb (0.23 kg). Other sizes also exist. Dynamite is a high explosive, which means it detonates rather than deflagrates. While trinitrotoluene (TNT) is used as the standard for gauging explosive power, dynamite has more than a 60% greater energy density than TNT.

22. 14-22 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Explosions This group comprises the majority of commercial and military blasting, such as dynamite, TNT, PETN, and RDX.

23. 14-23 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein High Explosives 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). Secondary explosives must be detonated by a primary explosive.

24. 14-24 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein High 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.

25. 14-25 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein High Explosives Triacetone triperoxide (TATP) is a homemade explosive that has been used by terrorist organizations. TATP can be made by combining acetone and peroxide in the presence of an acid. Its existence has led to the banning of most liquids on commercial aircraft.

26. Nitroglycerin (Initiating or primary high explosive) In its pure form, it is a contact explosive (physical shock can cause it to explode) and degrades over time to even more unstable forms. This makes it highly dangerous to transport or use. In this undiluted form, it is one of the most powerful high explosives, comparable to the newer military explosives Believe it or not, it is also used as heart medication – it is a vasodilator.

27. How does it work? The explosive power of nitroglycerin is derived from detonation: energy from the initial decomposition causes a pressure gradient that detonates the surrounding fuel.

28. Ingredients of Dynamite Original dynamite consisted of three parts nitroglycerin, one part diatomaceous earth and a small admixture of sodium carbonate. This mixture was formed into short sticks and wrapped in paper, with a “fuse” or a cord with a core of powder, that will transport the fire to the cylinder. blasting caps.Today, ammonium nitrate based dynamite is made and the fuse has been replaced with electronic detonators called blasting caps.

29. High Explosives Acronyms TNT = Trinitro Toluene PETN = PentaErythritol TetraNitrate, also known as pentrite. PETN is also used as a vasodilator, similar to nitroglycerin. Used as medicine for heart diseases. RDX = Cyclotrimethylenetrinitramine HMX or Octagon = Cyclotetramethylene- tetranitramine (related to RDX)

30. TNT (Non-initiating or secondary high explosive) Trinitro Toluene Most used by the military Used in grenades, bombs, shells, or even alone.

31. PETN PETN and TNT used together to make small-caliber projectiles Commercially used (mining, demolition, etc.) PETN is used in detonation cords or Primacords. These cords are used to create a series of explosions.

32. PETN primacords attached to demolition explosives.

34. Ammonium Nitrate Based Explosives They are: Water gels Emulsions ANFOs (Ammonium Nitrate Fuel Oil)

35. Water Gels Consistency of gel or toothpasteConsistency of gel or toothpaste Water-resistant, so good for explosions in or under bodies of water and wet conditionsWater-resistant, so good for explosions in or under bodies of water and wet conditions Contains:Contains: – Oxidizers : a mixture of ammonium nitrate and sodium nitrate, gelled together with a carbohydrate like guar gum (food thickener and emulsifier) –The fuel : is usually a combustible substance such as aluminum

36. Emulsion Explosives Have 2 distinct phasesHave 2 distinct phases –An oil phase –A water phase These emulsions containThese emulsions contain –An ammonium nitrate solution (oxidizer) surrounded by –A hydrocarbon (fuel) –An emulsifier such as glass, resin or ceramic microspheres to make the explosive less sensitive

37. ANFO Ammonium nitrate (oxidizer) or urea nitrate, soaked in a highly combustible hydrocarbon (fuel) – usually a fuel oil. Easy to make, safe to handle Ammonium nitrate is found in fertilizers, so ANFOs are a favorite type of homemade bombs.

38. ANFOs in trucks Dupont is a leading manufacturer of industrial and commercial ANFO

39. Homemade Explosives Molotov Cocktails TATP (Triacetone triperoxide) – a favorite amongst Middle Eastern Terrorists.

40. Molotov cocktail In its simplest form, a Molotov cocktail is a glass bottle containing petrol fuel usually with a source of ignition such as a burning, fuel soaked, rag wick held in place by the bottle's stopper. In action the fuse is lit and the bottle hurled at a target such as a vehicle or fortification. When the bottle smashes on impact, the ensuing cloud of petrol droplets and vapor is ignited, causing an immediate fireball followed by a raging fire as the remainder of the fuel is consumed. Other flammable liquids such as wood alcohol and turpentine have been used in place of petrol. Thickening agents such as motor oil have been added to the fuel, analogously to the use of napalm, to help the burning liquid adhere to the target and create clouds of thick choking smoke.

42. 14-42 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein History of High Explosives http://www.bing.com/videos/search?q=ch emistry+of+explosives&view=detail&mid =04419638D1DD42E4393D04419638D1D D42E4393D&first=0&FORM=NVPFVR #view=detail&mid=04419638D1DD42E43 93D04419638D1DD42E4393Dhttp://www.bing.com/videos/search?q=ch emistry+of+explosives&view=detail&mid =04419638D1DD42E4393D04419638D1D D42E4393D&first=0&FORM=NVPFVR #view=detail&mid=04419638D1DD42E43 93D04419638D1DD42E4393D

43. 14-43 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Follow that Case http://www.interfire.org/features/followTha tCase/episode001.asphttp://www.interfire.org/features/followTha tCase/episode001.asp

44. 14-44 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Homework Read Chapter 13, pages 458-468, #14-20

45. 14-45 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Exit Slip: December 3, 2014 Go to m.socrative.com and enter 417101 Question: What is the difference between low and high explosives?