TNT stands for
Trinitrotoluene
though is, by far, better well known by the initials of TNT. TNT was discovered by
Joseph Wilbrand in 1863 though it wasn't until later that it was recognized as an explosive.
Part of the 'beauty' of TNT is in the reaction of the explosion - two moles of TNT become 15 moles of hot gas and some carbon:
2C7H5N3O6 (s) ->
3N2 (g) + 7CO(g) + 5H2O (g) + 7C (s)
(2 units of TNT (solid) become 3 units of Nitrogen gas, 7 units of Carbon monoxide, 5 units of water vapor, and soot)
1 gram of TNT will produce on the order of 1 liter of gas - a 1000x increase in volume.
TNT itself is made by adding 3 moles of NO2 (most often by means
of nitric acid) to 1 mole of toluene (thus the name - Tri Nitro Toluene). To form TNT it is necessary to have a high enough reaction temperature - low reaction temperatures form mononitrotoluenes, and slightly higher reaction temperatures form the dinitro compounds.
Two facts make TNT an explosive:
- Chemical composition
- TNT contains carbon, oxygen, and nitrogen. When things with this
construction are burnt they forms three very stable gases - CO (carbon monoxide), CO2 (carbon dioxide) and N2 (nitrogen gas). These gases have strong bonds and the formation releases a large amount of energy. Most explosives have this structure - a nitrogen or oxygen group (often the Nitro group of NO2) attached to an organic backbone (in this case toluene - C6H5CH3)
H H H O-N-O
\ / \ /
C - C H O C - C H
// \\ | | // \\ |
H-C C--C-H + 3x O-N-O ==> N-C C--C-H
\ / | | | \ / |
C = C H ? O C = C H
/ \ / \
H H H O-N-O
There are 16 different possible trinitrotoluenes with the possible bonding spots for the Nitro groups. Each one of these has different characteristics (melting point, boiling point, etc..) Only symmetrical trinitrotoluene (2,4,6-trinitrotoluene) is TNT (shown above).
- Chemically Unstable
- As seen above, the nitro groups are rather closely packed. This packing produces strain on the structure of the molecule so that it does not take much force to break a bond, at which point, the molecule will fly apart. However, it is not too unstable. TNT can be handled safely and will not suddenly explode - it takes the pressure wave of a detonator to cause the explosion.
TNT actually has less potential energy stored than that of standard gasoline. However, when TNT explodes, this energy is unleashed with much higher velocity that causes the blast pressure. TNT has a detonation velocity of 6,940 m/s (compare - gasoline at 0.34 m/s)
While TNT is not the most powerful of explosives that exist, it is rather easy to make, relatively safe to handle (it does not explode with ordinary shocks or jarring as does nitroglycerin), and has a reasonable explosive power while being fairly stable and only moderately toxic. The low melting point allows it to be melted down and easily cast into the appropriate shape.
As mentioned above, TNT is toxic. In places where bombs have exploded or land mines have been left, there is often some TNT residue left over that may contaminate the soil for years to come. Cleanup of TNT is a very important issue for many and has been researched at the Department of Energy's Argonne National Laboratory - mix it with molasses.
Cleanup of TNT involves excavating the soil to remove rocks and stones, adding water and then processing the soil (now a slurry) in tanks called bioreactors. Adding Molasses to these bioreactors provides food for naturally occurring bacteria that live in the soil that decompose the TNT - it is an excellent source of nitrogen. After the slurry has been processed, the water is removed and the clean soil can be returned. This process is known as bioremediation.
- Appearance: pale yellow crystal
- Specific gravity: 1.65
- Melting point: 82 C (147 F)
- Burn temperature: 295 C (531 F) in the open
- Does not react with metals
- Does not absorb moisture
- Insoluble in water
- Soluble in benzene and acetone
- Reacts with reducing agents
- Able to be absorbed through the skin. Symptoms include: