Nitroglycerine
- Nitroglycerine mixed with a silica based mineral. It was safer and more reliable to detonate as it could only be detonated deliberately, and due to Nobel’s system of explosives detonating other explosives.
- Nitroglycerine mixed with Collodion (a form of nitrated cellulose). It had the same safety benefits as dynamite and was a more powerful explosive.
- Cordite is a mixture of cellulose trinitrate and glycerol trinitrate and other substances. It was, and still is, used as a smokeless propellant for shells. In its production, the addition of propanone turns it into a jelly-like substance, which dries out to form a granular solid.
- TNT contains nitro groups as opposed to nitrate groups. It does not react with metals, so it can be put into shells for missiles and bombs; however it creates health problems for the workers involved in production.
Trinitrotoluene
For a reaction to be explosive it needs to take place very quickly, be exothermic and give off gases. The balanced equation for the explosive reaction of gunpowder is as follows:
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4KNO3 (s) + 7C(s) + S(s) 3CO(g) +3CO2 (g) +N2 (g) +K2CO3 (s) + K2S(s)
This reaction is rapid and exothermic and therefore explosive. Gunpowder is an example of a low explosive. It is capable of undergoing relatively slow combustion under suitable conditions, but is explosive when confined. Gunpowder and other low explosives’ prime military use are as propellants for missiles and other projectiles. High explosives, such as nitroglycerine cause uncontrollable blasts. They are usually compounds and do not require confinement to be explosive.
An ideal explosive reaction would have a low activation energy, its own supply of oxygen, gases as products and occur rapidly and exothermically.
An example of how amounts of oxygen in reactants can increase the explosive power of a reaction is the oxidation of propane in a balloon. When a propane-filled balloon is ignited there is a small explosion. When the balloon is filled with propane and >10% of oxygen the resultant explosion is much more powerful.
C3H8 (g) + 5O2 (g) 3CO2 (g) + 4H2O (g)
As the equation shows, the reaction requires oxygen. If the oxygen is made more readily available, by mixing with the propane in the balloon, the reaction occurs more rapidly and will therefore be more explosive.
Propanone is used to turn a mixture of cellulose trinitrate and glycerol trinitrate into a jelly like substance in the final stages of cordite production.
At the start of the First World War (WW1) the primary method of propanone manufacture was developed by Chain Weidman. He had developed a process that produced propanone from bacterial fermentation of maize-starch. Maize was however, not grown in the UK and when supplies from the USA were lost to the German U-boats, a new source was needed. Conkers were used as a substitute for the maize, although
nowhere near as efficient.
When the war ended this method of production was not further developed. The process for propanone manufacture after the war was from the catalysed breakdown of propan-2-ol from propene, from crude oil fractions.
C3H7OH Cu-catalyst 500°C 400 kPa C3H6O + H2
During WW1 there was increased demand for cordite and TNT for use by the men who were fighting. The task of producing it was set to the women of Britain.
The manufacturing of cordite was a very hazardous process. The necessary nitro cellulose was produced by stirring cotton with a mixture of nitric and sulphuric acids in open vats. These open vats allowed particles of acid onto skin, clothes and into the respiratory system of workers, causing burns and breathing problems. Liquid was also kneaded into portions of the nitrocotton by hand.
In terms of severity of hazards, TNT production was the worst of the major munitions work during the war. The TNT caused the skin to go yellow and ginger hair to turn green. TNT was evidently common although unidentified in most cases. In addition to chemical hazards were the risks of accidental explosions which claimed many lives in this period.
Presently, we are much more aware of hazards involved in production
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of these substances. Most stages are carried out mechanically, and those stages which
require human involvement are highly regulated. Any person coming into contact with harmful substances wears protective clothing and has regular medical check-ups. Also the media interest in cases where people have unwittingly caused themselves harm through their professions has made it impossible for cases to be covered up as they were in previous years.
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Summary
Rapid exothermic oxidation reactions, releasing gases under pressure are the basis of explosives. Their power (brisance) is determined by availability of oxygen within reactants. All require detonation, through ignition or impact. Their military usefulness additionally requires their ability for safe preparation, storage and precise activation.
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