Trinitrotoluene

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Trinitrotoluene (TNT, or Trotyl) is a pale yellow crystalline aromatic hydrocarbon compound that melts at 354 K (178 °F, 81 °C). Trinitrotoluene is an explosive chemical and a part of many explosive mixtures, such as when mixed with ammonium nitrate to form amatol. It is prepared by the nitration of toluene C₆H₅C H₃; it has a chemical formula of C₆H₂(N O₂)₃C H₃, and IUPAC name 2,4,6-trinitrotoluene.

In its refined form, trinitrotoluene is very stable, and, unlike nitroglycerin, it is insensitive to friction, blows, and jarring. This means that it must be set off by a detonator. It does not react with metals or absorb water, and so, unlike dynamite, it can be safely stored for many years. It is however readily acted upon by alkalis to form unstable compounds that are very sensitive to heat and impact.

Amounts of TNT are used as units of energy, especially for expressing nuclear weapon yield, based on a specific combustion energy of TNT of 4.184 MJ/kg (or one calorie—specifically a thermochemical calorie—per milligram). Hence, 1 kt TNT = 4.184 TJ, 1 Mt TNT = 4.184 PJ. Note that chemical explosives release less energy per kilogram than everyday household products like fat (38 MJ/kg) and sugar (17 MJ/kg); they do, however, release their combustion energy much more rapidly. One reason for their low power is that they contain their oxidant as well as the fuel — an explosive does not use atmospheric oxygen. The density of pure TNT (without any additives like sawdust or aluminium) is 1.654 g/cm³.

1 Toxicity
2 History
3 Preparation
4 See also
5 External links

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Toxicity

Some military testing grounds are contaminated with TNT. Wastewater from munitions programs including contamination of surface and subsurface waters may be colored pink as the result of TNT and RDX contamination. Such contamination, called pinkwater, may be difficult and expensive to remediate.

TNT is quite toxic. It can also be absorbed through the skin, and will cause irritation and bright yellow staining. During the First World War, munition workers who handled the chemical found that their skin turned bright yellow, which led to the nickname "canary girls" or simply "canaries" to describe such workers. TNT would also eventually make ginger hair turn green. A 1916 British Government inquiry on female workers at the Royal Arsenal, Woolwich found that 37% had severe pains due to loss of appetite, nausea and constipation, 25% suffered from dermatitis, and 34% experienced changes in menstruation. Before respirators and protective grease applied to the skin were introduced, about 100 workers died from the disease.

People exposed to Trinitrotoluene over a prolonged period tend to experience anemia and abnormal liver functions. Blood and liver effects, spleen enlargement and other harmful effects on the immune system have also been found in animals that ingested or breathed trinitrotoluene. There is evidence that TNT adversely affects male fertility, and TNT is listed as a possible human carcinogen. Consumption of TNT produces black urine.

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History

TNT was first made in 1863 by a German chemist Joseph Wilbrand, but its potential was not seen for several years, mainly because it was so hard to detonate and because it was less powerful than other explosives. Among its advantages, however, is its ability to be safely melted using steam or hot water, and so poured molten into shell cases. It is also so insensitive that, for example, in 1910 it was exempted from the British 1875 Explosives Act from actually being considered an explosive for the purposes of manufacture and storage.

The German armed forces adopted it as an artillery shell filling in 1902, and the British gradually started using it as replacement for lyddite in 1907. A particular advantage that it gave the German Navy in the First World War was to detonate after the TNT-filled armour-piercing shells had penetrated the armour of British capital ships, whereas the British lyddite-filled shells tended to explode as soon as they struck the German armour, and thus expended their energy outside of the ship.

Because of the insatiable demand for trinitrotoluene during the war, it was frequently mixed with 40%-80% ammonium nitrate, producing an explosive called amatol. Although nearly as powerful as TNT, amatol suffered from the slight disadvantage of being hygroscopic. Another variation called minol, consisting of amatol mixed with about 20% aluminum powder, was used by the British in mines and depth charges.

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Preparation

Prepare a nitrating solution of 160 mL of 95% sulphuric acid and 105 mL of 75% nitric acid in a 500-mL beaker set in a salt-ice bath. Mix the acids very slowly to avoid the generation of too much heat. Allow the mixture to cool to room temperature. Slowly add the nitrating solution dropwise, with a pipette or burette, to 115 mL of toluene in a 600-mL beaker while stirring rapidly. Maintain the temperature of the beaker during the addition at 30-40 °C by using either a cold water or salt-ice bath. The addition should require 60-90 minutes. After the addition, continue stirring for 30 minutes without any cooling, then let the mixture stand for 8-12 hours in a separatory funnel. The lower layer will be spent acid and the upper layer should be mononitrotoluene. Drain the lower layer and keep the upper layer.

Dissolve one-half of the previously prepared mononitrotoluene and 60 mL of 95% sulphuric acid in a 500-mL beaker set in a cold water bath. Prepare a nitrating solution of 30 mL of 95% sulfuric acid very slowly and 36.5 mL of 95% nitric acid in a 100-mL beaker. Preheat the beaker of mononitrotoluene to 50°C. Add the nitrating acid to the beaker of mononitrotoluene drop by drop while stirring rapidly (with a pipette or burette). Regulate the rate of addition to keep the temperature of the reaction between 90-100 °C. The addition will require about 1 hour. After the addition, continue stirring and maintaining the temperature at 90-100 °C for 2 hours. If the beaker is allowed to stand, a layer of dinitrotoluene will separate. It is not necessary to separate the dinitrotoluene from the acid in this step.

While stirring the beaker of dinitrotoluene, heated to 90 °C, slowly add 80 mL of 100% fuming sulphuric acid, (containing about 15% SO3), by pouring from a beaker. Prepare a nitrating solution of 40 mL of 100% sulfuric acid, with 15% SO3, and 50 mL of 99% nitric acid. Very slowly add the nitrating acid to the beaker of dinitrotoluene, with a pipet or buret, drop by drop while stirring rapidly. Regulate the rate of addition to keep the temperature of the reaction between 100-115 °C. It may become necessary to heat the beaker after three-quarters of the acid has been added in order to sustain the 100-115 °C temperature. The addition will require about 90-120 minutes.

Maintain the stirring and temperature at 100-115 °C for 2 hours after the addition is complete. Allow the beaker to sit undisturbed for 8-12 hours. It should form a solid mass of trinitrotoluene crystals. Pour the contents of the beaker over a Buchner funnel without any filter paper to collect the bulk of the crystals, save the acidic filtrate as well. Break up the collected crystals and wash them with water to remove any excess acid. Add the collected acid and wash filtrates to a large volume of water, this will cause any remaining trinitrotoluene to precipitate. Decant off as much of the water as possible and combine these crystals with the previous ones on the funnel. Drown the crystals in a large volume of water, filter to collect them, and wash several times with water (by adding them to a beaker of water, heating the water enough to melt the crystals while stirring rapidly).

Repeat the melting and stirring with a fresh batch of water three or four times to wash thoroughly. After the last washing, granulate the trinitrotoluene by allowing it to cool slowly under hot water while continuing to stir. Filter to collect the crystals and allow to dry.

The TNT can be further purified by recrystallizing it from ethyl alcohol, (by dissolving the crystals in 60 °C ethyl alcohol and allow the solution to cool slowly. A second method of purification is to digest the TNT in 5 times its weight of 5% sodium bisulfite solution heated to 90 °C while stirring rapidly for 30 minutes. Wash the crystals with hot water until the washings are colorless, then allow the crystals to granulate as before.

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