explosive
Any material capable of a sudden release of energy and the rapid formation of a large volume of gas, leading, when compressed, to the development of a high-pressure wave (blast).
Types of explosive
Combustion and explosion differ essentially only in rate of reaction, and many explosives (called
low explosives) are capable of undergoing relatively slow combustion under suitable conditions.
High explosives produce uncontrollable blasts. The first low explosive was
gunpowder; the first high explosive was
nitroglycerine.
19th-century inventions Gunpowder's high activation energy made it inconvenient as an explosive, and during the 19th century other chemicals with a lower activation energy superseded it, including mercury fulminate (Hg(CNO)2), lead azide (Pb(N2)2), and silver fulminate (AgCNO). Soon afterwards, the first organic explosives were developed. These were based on ethanol, glycerol, and cellulose, and included nitroglycerine, produced by adding nitric acid to glycerol. Another organic-based explosive is guncotton, a mixture of nitric and sulphuric acid on cotton fibre, invented 1845 by Swiss chemist Christian Schoenbein. Guncotton is highly reactive, and is today used as a propellant. In 1867, Alfred Nobel produced dynamite by mixing nitroglycerine with kieselguhr, a fine, chalklike material. |
Modern explosives Other explosives now in use include trinitrotoluene (TNT); ANFO (a mixture of ammonium nitride and fuel oil), which is widely used in blasting; and pentaerythritol tetranitrate (PETN), a sensitive explosive with high power. Military explosives are often based on cyclonite (also called RDX), which is moderately sensitive but extremely powerful. Even more powerful explosives are made by mixing RDX with TNT and aluminium. Plastic explosives, such as Semtex, which is odourless and difficult to detect, are based on RDX mixed with oils and waxes. The explosive force of atomic and hydrogen bombs arises from the conversion of matter to energy according to Einstein's mass–energy equation, E = mc2. |
