[DL] Explosives (definitions and history){long}

["Heivilin, Jim" <banzai@missouri.edu>]

From (again) the Encyclopaedia Britannica online
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trinitrotoluene
(tnt) , a pale yellow, solid organic nitrogen compound used chiefly as an
explosive, prepared by stepwise nitration of toluene. Because Tnt melts at
82 C (178 F) and does not explode below 240 C (464 F), it can be melted in
steam-heated vessels and poured into casings. It is relatively insensitive
to shock and cannot be exploded without a detonator. For these reasons it is
the most favoured chemical explosive, extensively used in munitions and for
demolitions. 

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dynamite
blasting explosive, patented in 1867 by the Swedish physicist Alfred Nobel.
Dynamite is based on nitroglycerin but is much safer to handle than
nitroglycerin alone. By mixing the nitroglycerin with kieselguhr, a porous
siliceous earth, in proportions that left an essentially dry and granular
material, Nobel produced a solid that was resistant to shock but readily
detonable by heat or percussion. Later, wood pulp was substituted as the
absorbent, and sodium nitrate was added as an oxidizing agent to increase
the strength of the explosive. Nobel also invented gelatinous dynamite, a
mixture of nitrocellulose and nitroglycerin. Ammonium nitrate was later
substituted for part of the nitroglycerin to give a safer and less expensive
explosive called extra dynamite. See also explosive. 

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nitroglycerin
also called GLYCERYL TRINITRATE, a powerful explosive and an important
ingredient of most forms of dynamite. It is also used with nitrocellulose in
some propellants, especially for rockets and missiles, and it is employed as
a vasodilator in the easing of cardiac pain. 

Pure nitroglycerin is a colourless, oily, somewhat toxic liquid having a
sweet, burning taste. It was first prepared in 1846 by the Italian chemist
Ascanio Sobrero by adding glycerol to a mixture of concentrated nitric and
sulfuric acids. The hazards involved in preparing large quantities of
nitroglycerin have been greatly reduced by widespread adoption of continuous
nitration processes. 

Nitroglycerin, with the molecular formula C3H5(ONO2)3, has a high nitrogen
content (18.5 percent) and contains sufficient oxygen atoms to oxidize the
carbon and hydrogen atoms while nitrogen is being liberated, so that it is
one of the most powerful explosives known. Detonation of nitroglycerin
generates gases that would occupy more than 1,200 times the original volume
at ordinary room temperature and pressure; moreover, the heat liberated
raises the temperature to about 5,000 C (9,000 F). The overall effect is the
instantaneous development of a pressure of 20,000 atmospheres; the resulting
detonation wave moves at approximately 7,700 m per second (more than 17,000
miles/h). Nitroglycerin is extremely sensitive to shock and to rapid
heating; it begins to decompose at 50-60 C (122-140 F) and explodes at 218 C
(424 F). 

The safe use of nitroglycerin as a blasting explosive became possible after
the Swedish chemist Alfred B. Nobel developed dynamite in the 1860s by
combining liquid nitroglycerin with an inert porous material such as
charcoal or diatomaceous earth. Nitroglycerin plasticizes collodion (a form
of nitrocellulose) to form blasting gelatin, a very powerful explosive.
Nobel's discovery of this action led to the development of ballistite, the
first double-base propellant and a precursor of cordite. 

A serious problem in the use of nitroglycerin results from its high freezing
point (13 C [55 F]) and the fact that the solid is even more shock-sensitive
than the liquid. This disadvantage is overcome by using mixtures of
nitroglycerin with other polynitrates; for example, a mixture of
nitroglycerin and ethylene glycol dinitrate freezes at -29 C (-20 F). 

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(so we find freezing nitro isn't necessarily the best answer)
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Black powder

History of black powder

It may never be known with certainty who invented the first explosive, black
powder, which is a mixture of saltpetre (potassium nitrate), sulfur, and
charcoal (carbon). The consensus is that it originated in China in the 10th
century, but that its use there was almost exclusively in fireworks and
signals. It is possible that the Chinese also used black powder in bombs for
military purposes, and there is written record that in the mid-13th century
they put it in bamboo tubes to propel stone projectiles. 

There is, however, some evidence that the Arabs invented black powder. By
about 1300, certainly, they had developed the first real gun, a bamboo tube
reinforced with iron, which used a charge of black powder to fire an arrow. 

A strong case can also be made that black powder was discovered by the
English medieval scholar Roger Bacon, who wrote explicit instructions for
its preparation in 1242, in the strange form of a Latin anagram, difficult
to decipher. But Bacon read Arabic, and it is possible that he got his
knowledge from Arabic sources. 

Some scholars attribute the invention of firearms to an early 14th-century
German monk named Berthold Schwarz. In any case they are frequently
mentioned in 14th-century manuscripts from many countries, and there is a
record of the shipment of guns and powder from Ghent to England in 1314. 

Not until the 17th century was black powder used for peaceful purposes.
There is a doubtful claim that it was used in mining operations in Germany
in 1613 and fairly authentic evidence that it was employed in the mines of
Schemnitz, Hungary (modern Banská Stiavnica, Czechoslovakia), in 1627. For
various reasons, such as high cost, lack of suitable boring implements, and
fear of roof collapse, the use of black powder in mining did not spread
rapidly, though it was widely accepted by 1700. The first application in
civil engineering was in the Malpas Tunnel of the Canal du Midi in France in
1679. 

For 300 years the unvarying composition of black powder has been
approximately 75 percent saltpetre (potassium nitrate), 15 percent charcoal,
and 10 percent sulfur. The saltpetre was originally extracted from compost
piles and animal wastes. Deposits found in India provided a source for many
years. During the 1850s tremendous quantities of sodium nitrate were
discovered in Chile, and saltpetre was formed by reaction with potassium
chloride, of which there was a plentiful supply. 

Chilean nitrate was not at first considered satisfactory for the manufacture
of black powder because it too readily absorbed moisture. Lammot du Pont, an
American industrialist, solved this problem and started making sodium
nitrate powder in 1858. It became popular in a short time because, although
it did not produce as high a quality explosive as potassium nitrate, it was
suitable for most mining and construction applications and was much less
expensive. To distinguish between them, the potassium nitrate and sodium
nitrate versions came to be known as A and B blasting powder respectively.
The A powder continued in use for special purposes that required its higher
quality, principally for firearms, military devices, and safety fuses.

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Jim H.