Explosives1. Primary (Initiators): Do not burn but detonate if ignited (mercury fulminate).
2. Low (Propellants): Burn at steady speed and detonated only under extreme conditions (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. Upon returning to England in 1247, Bacon became interested in science. His experiments using lenses/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 in 1266 Bacon wrote to Pope Clement IV proposing a science encyclopedia. Pope Clement IV misunderstood 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 and explosives? While
composing the encyclopedia, Bacon became aware of the discovery by the
Asian alchemists. This prompted Bacon to experiment with mixtures of saltpeter,
sulfur, and a new ingredient (charcoal); Bacon had made black powder (the
early form of gunpowder).
One hundred years later friar Berthold Shwarts looked into this black
powder. Schwarts took a long iron tube and closed one end except for a
tiny hole. He filled the tube with black 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 had invented the "gun."
Nitroglycerin/Nitrocellulose
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 could be detonated by the touch of a feather.
One mole of nitroglycerine (227g) releases 1427 kJ upon exploding. It's
volume increases from a liquid of approximately 1/4 L to gases occupying
approximately 650 L.
In 1845, Christian Schoenbein made nitrocellulose (guncotton) by dipping
cotton in a mixture of nitric and sulfuric acids. However, the material
obtained was too unstable to be used as an explosive. Major E. Schultze
(1860) of the Prussian army produced a useful propellant. He nitrated small
pieces of wood by placing them in nitric acid and impregnated the pieces
with barium and potassium nitrates. The purpose of the latter was to provide
oxygen to burn the incompletely nitrated wood. Schultze's powder was
highly successful in shotguns 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 dissolved nitrocellulose 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
satisfactory results in all types of guns.
Alfred
Nobel (1833-1896)
Alfred Nobel mixed nitroglycerin and silica (SiO2)
forming a paste that could be safely used as an explosive--he patented
this material as dynamite (1867). Nobel also invented the blasting cap
to provide a safe and dependable means for detonating. Nobel's original
blasting cap consisted of 80% mercury fulminate [Hg(ONC)2]
and 20% potassium chlorate. Blsting caps today are lead azide [Pb(N3)2]
due to its greater stability when stored under hot 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 inventions became an instrument of war, established
the Nobel Prize in categories reflecting his interests (Chemistry, Physics,
Medicine, Literature, Peace).
Ballistite
In 1887 Nobel introduced ballistite, 40% nitrocellulose/60% nitroglycerin
blended together with diphenylamine. When cut into flakes, this made an
excellent propellant and it continued in use for over 75 years. The British
refused to recognize Nobel's patent and developed a number of similar products
under the generic name cordite.
Cordite
Sir James Dewar (1842-1923) is best known for his work with low-temperature--he
invented the thermos and produced both hydrogen and oxygen in liquid form.
Along with Sir 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 ordinary
shocks and therefore must be set off by a detonator. TNT is often mixed
with other explosives such as ammonium nitrate to form amatol. Because
it is insensitive to shock and must be exploded with a detonator, it
is the most favored explosive used in munitions and construction.
Why do nitro groups (NO2)
lead to unstable compounds? Nitrogen has charge of +1
and nitro group have a strong tendency to withdraw (pull) electrons from
other parts of the compound. Attaching three 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 more sensitive 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 in mixtures with other explosives, oils, or waxes. RDX
has a high degree of stability in storage and is considered the most powerful
high explosive. RDX is the main ingredient in plastic explosives.
ANFO (Ammonium Nitrate Fertilizer)
Although
ammonium nitrate (NH4NO3)
is a benign fertilizer, when mixed with fuel oil it becomes a deadly bomb
(ANFO). Dynamite or TNT are usually used to detonate ANFO (military manuals
suggest using one pound of TNT for every fifty pounds of fertilizer). The
deadly Oklahoma City Bomb was ANFO.
du
Pont de Nemours (1771-1834)
DuPont is one of the oldest continuously operating industrial enterprises
in the world. The company was established in 1802 near Wilmington, Delaware,
by a French immigrant, Eleuthére Irénée du Pont de
Nemours, to produce black powder. The company was capitalized at $36,000
with 18 shares* at $2000 each. du Pont de Nemours had been a student of
Antoine Lavoisier, the father of modern chemistry, and he brought to America
some 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 an explosives 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 by terrorists. Here are 4 methods:
1. Canines: ATF's
explosives-detecting canine training program was established in 1992. Although
not high tech, canines can detect minute quantities for a variety of explosives.
2. Chemical Sensor: Portable
system the size of soccer ball is being developed by Sandia Laboratories
that can detect/identify smallest traces of explosives. Known as chemical
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 laser
radiation with traces of explosive causes micro bursts. Explosives are
identified from light generated by bursts.