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Cyclotrimethylene trinitramine, also known as RDX, cyclonite, or hexogen, is an explosive material widely used by the military.
There are many interpretations of its acronym including (but not limited to) Royal Demolition eXplosive and Research Department Explosive. In fact the latter is nearest to the mark. New explosives were given an identification number preceded by the letters 'RD' indicating 'Research and Development'. For some reason, this explosive was unable to be given a number (the story goes that the department that issued the numbers had just blown itself up - but this may be apocryphal). Instead the letter 'X' was appended to indicate 'unknown' with the intention of adding the number later. Although a number was issued, the term 'RDX' stuck.
In its pure synthesised state it is a white crystalline solid. As an explosive it is usually used in mixtures with other explosives and plasticizers or desensitizers. It is stable in storage and is considered the most powerful and brisant of the military high explosives.
RDX forms the base for a number of common military explosives: Composition A (wax-coated, granular explosive consisting of RDX and plasticizing wax), composition A5 (mixed with 1.5% stearic acid), composition B (castable mixtures of RDX and TNT), composition C (a plastic demolition explosive consisting of RDX, other explosives, and plasticizers), composition D, HBX (castable mixtures of RDX, TNT, powdered aluminum, and D-2 wax with calcium chloride), H-6, Cyclotol and C-4.
Properties
It is a colourless solid, of density 1.82 g/cm³. It is obtained by reacting concentrated nitric acid on hexamine. It is a heterocycle and has the shape of a ring. It starts to decompose at about 170°C and melts at 204°C. Its structural formula is: hexahydro-1,3,5-trinitro-1,3,5-triazine or (CH2-N-NO2)3
At room temperatures, it is a very stable product. It burns rather than explodes, and only detonates with a detonator, being unaffected even by small arms fire. It is less sensitive than pentaerythritol tetranitrate (PETN). However, it is very sensitive when crystalized, below -4°C.
Under normal conditions, RDX has a Figure of Insensitivity of 80.
The manufacture of RDX can easily pollute soil and groundwater.
History
The discovery of RDX dates from the 1890s when a German (Hans Henning) offered it as a medicine. Its explosive properties were not recognized until 1920 (Herz?). In the 1920s RDX was produced by the direct nitration of hexamine. It was only in 1940 that an efficient production method was found, possibly at the McGill University Department of Chemistry (Meissner?). It was widely used during WW II, often in explosive mixtures with TNT such as Torpex (TNT (42%),RDX (40%) and aluminium (18%)). RDX was used in one of the first plastic explosives.
Laboratory Synthesis
- Add 335 mL of 100% nitric acid, free of nitrogen oxides in a 500-mL beaker,
- Cool the acid to below 30 °C.
- Add 75 g of hexamine in small portions, while stirring the mixture. NOTE: During the addition toxic fumes will be produced.
- During the addition the temperature must be kept between 20 °C to 30 °C.
- After the hexamine has dissolved, slowly heat the mixture to 55 °C while stirring.
- Keep the mixture between 50-55 °C for 5 minutes, keep stirring.
- Now cool the mixture to 20 °C then let sit for 20 minutes.
- Slowly dilute the mixture with four times its volume of cool water to precipitate the RDX from solution. Most of the RDX will precipitate in several hours; after 24 hours there will be no additional precipitation of RDX.
- Filter the RDX that precipitated from the mixture and add 1 L of 5% sodium bicarbonate solution to adjust the pH to neutral.
- Dry the pH balanced RDX at room tempature; after drying the RDX is ready to use.
- If RDX of higher purity is desired, recrystalize from acetone.
de:Hexogenpl:Heksogen
ru:Гексоген
sl:heksogen
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