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ExplosivesExplosives, highly exothermic chemical reactions that produce expanding gases were

first made by Asian alchemists more than one thousand years ago when they discoveredmixtures of saltpeter (KNO 3) and sulfur could be detonated. Explosives are classified as:1. Primary (Initiators): Do not burn but detonate if ignited (mercury fulminate).2. Low (Propellants): Burn at steady speed and detonated only under extremeconditions (gunpowder).3. High: Release large amounts of energy when detonated (nitroglycerine).

Roger Bacon (1220-1292)

Born England, Bacon studied geometry/arithmetic/music/astronomy in France. Uponreturning to England in 1247, Bacon became interested in science. His experiments usinglenses/mirrors resemble modern scientific approaches. In 1257 Bacon left the University of Oxford and entered the Order of Friars Minor. His interests in the sciences continued and in1266 Bacon wrote to Pope Clement IV proposing a science encyclopedia. Pope Clement IVmisunderstood what Bacon was proposing and assumed the encyclopedia already existed.

So when the Pope asked to see the encyclopedia, Bacon rapidly began work on the project.The project was carried out in secret since Bacon's superiors opposed what he was doing.Bacon hoped to demonstrate that science had a rightful role in the university curriculum.But In 1268 Pope Clement IV died along with Bacon's chance to see the project accepted(only parts of the manuscript were ever published).

What is the connection between Bacon andexplosives? While composing the encyclopedia, Baconbecame aware of the discovery by the Asian alchemists. Thisprompted Bacon to experiment with mixtures of saltpeter,sulfur, and a new ingredient (charcoal); Bacon had madeblack powder (the early form of gunpowder).One hundred years later friar Berthold Shwarts looked intothis black powder. Schwarts took a long iron tube andclosed one end except for a tiny hole. He filled the tube withblack powder and stuffed a small pebble in it. He touched a

flame to the tiny hole and the pebble shot through the air with great speed. Schwarts hadinvented the "gun."

Nitroglycerin/Nitrocellulose

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Five hundred years after Berthold Schwarts invented the gun, Ascano Sobrero (Italian)mixed nitric acid and glycerin to obtain nitroglycerine--an explosive so unstable that it couldbe detonated by the touch of a feather. One mole of nitroglycerine (227g) releases 1427 kJupon exploding. It's volume increases from a liquid of approximately 1/4 L to gasesoccupying approximately 650 L.

In 1845, Christian Schoenbein made nitrocellulose (guncotton) by dipping cotton in amixture of nitric and sulfuric acids. However, the material obtained was too unstable to beused as an explosive. Major E. Schultze (1860) of the Prussian army produced a usefulpropellant. He nitrated small pieces of wood by placing them in nitric acid and impregnatedthe pieces with barium and potassium nitrates. The purpose of the latter was to provideoxygen to burn the incompletely nitrated wood. Schultze's powder was highly successful inshotguns but was too fast for cannon or even most rifles. In 1884 a French chemist, Paul

Vieille, made the first smokeless powder as it is now known. He partially dissolvednitrocellulose in a mixture of ether/alcohol, then he rolled it into sheets and cut into flakes.When the solvent evaporated, it left a hard, dense material. This product gave satisfactoryresults in all types of guns.

Alfred Nobel (1833-1896)

Alfred Nobel mixed nitroglycerin and silica (SiO 2) forming a paste that could be safely usedas an explosive--he patented this material as dynamite (1867). Nobel also invented theblasting cap to provide a safe and dependable means for detonating. Nobel's originalblasting cap consisted of 80% mercury fulminate [Hg(ONC) 2] and 20% potassium chlorate.Blsting caps today are lead azide [Pb(N 3)2] due to its greater stability when stored underhot conditions.

A French newspaper--thinking Alfred and not his brother had died in 1886--ran his obituary

under the headline, "The merchant of death is dead." Nobel, displeased that his inventionsbecame an instrument of war, established the Nobel Prize in categories reflecting hisinterests (Chemistry, Physics, Medicine, Literature, Peace).

Ballistite In 1887 Nobel introduced ballistite, 40% nitrocellulose/60% nitroglycerin blended togetherwith diphenylamine. When cut into flakes, this made an excellent propellant and itcontinued in use for over 75 years. The British refused to recognize Nobel's patent anddeveloped a number of similar products under the generic name cordite.

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Cordite Sir James Dewar (1842-1923) is best known for his work with low-temperature--heinvented the thermos and produced both hydrogen and oxygen in liquid form. Along withSir Frederick Abel, Dewar invented cordite (1889). This smokeless gunpowder consists of nitroglycerin, guncotton, and a petroleum substance gelatinized by addition of acetone.

Trinitrotoluene (TNT) Trinitrotoluene is a high explosive that is unaffected by ordinaryshocks and therefore must be set off by a detonator. TNT is oftenmixed with other explosives such as ammonium nitrate to formamatol. Because it is insensitive to shock and must be exploded witha detonator, it is the most favored explosive used in munitions andconstruction.Why do nitro groups (NO 2 ) lead to unstablecompounds? Nitrogen has charge of +1 and nitro group have a

strong tendency to withdraw (pull) electrons from other parts of the compound. Attachingthree nitro groups to a compound leads to an extremely unstable situation.

Pentaerythritoltetranitrate (PETN) PETN is a powerful high explosive with 140% the power of TNT. Because PETN is moresensitive to shock or friction than TNT, it is primarily used in small caliber ammunition.

Cyclotrimethylenetrinitramine (RDX) Also called RDX, Cyclotrimethylenetrinitramine is a white crystalline solid usually used inmixtures with other explosives, oils, or waxes. RDX has a high degree of stability in storageand is considered the most powerful high explosive. RDX is the main ingredient in plasticexplosives.

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ANFO (Ammonium Nitrate Fertilizer)

Although ammonium nitrate (NH 4NO3) is a benign fertilizer, when

mixed with fuel oil it becomes a deadly bomb (ANFO). Dynamite orTNT are usually used to detonate ANFO (military manuals suggestusing one pound of TNT for every fifty pounds of fertilizer). Thedeadly Oklahoma City Bomb was ANFO.

du Pont de Nemours (1771-1834)

DuPont is one of the oldest continuously operating industrial enterprises in the world. Thecompany was established in 1802 near Wilmington, Delaware, by a French immigrant,Eleuthre Irne du Pont de Nemours, to produce black powder. The company wascapitalized at $36,000 with 18 shares* at $2000 each. du Pont de Nemours had been astudent of Antoine Lavoisier, the father of modern chemistry, and he brought to Americasome new ideas about the manufacture of consistently reliable gun and blasting powder.Due to increasing competition in the early 1900s, DuPont made the transition from anexplosives manufacturer to a diversified chemical company.* The $2000 investment in 1802 is worth approximately $2.5 billion today.

Detecting Explosives Today's challenge is not safe handling of explosives but early detection when used byterrorists. Here are 4 methods:

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1. Canines: ATF's explosives-detecting canine training program was established in 1992. Although nothigh tech, canines can detect minute quantities for a variety of explosives. 2. Chemical Sensor: Portable system the size of soccer ball is being developed bySandia Laboratories that can detect/identify smallest traces of explosives. Known aschemical sensor system, molecules are collected on a fiber and "ion mobility spectrometer"identifies type of explosive.3. Neutron Beam: Technology called Prompt Gamma Neutron Activation Analysis(PGNAA) directs beam of neutrons. When neutrons contact contaminant, they instantly

produce high energy gamma rays. Explosives are identified from energy of gamma rays.4. Lasers: Carbon dioxide laser scans/analyzes baggage surfaces. The interaction of laserradiation with traces of explosive causes micro bursts. Explosives are identified from lightgenerated by bursts.