What is a gasoline explosive

Oxidising and explosive substances
Try to show in the film only!
 




 
   
Lesson schedule
 
The pupils are less familiar with the “flame over circle” symbol. Oxidizing substances on their own are usually relatively harmless if they are not mixed with combustible substances. The effect of an oxidizing substance is illustrated by means of a film: It is shown that even the mixing of flammable substances with oxidizing substances can be dangerous.
 


Potassium chlorate and red phosphorus


Explosion when touched
 
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This film demonstration is particularly impressive when the students receive additional information about the potential dangers of potassium chlorate. The mixtures are known from the cartridges for toy guns. Mixtures of potassium chlorate with red phosphorus explode from impact and friction. They're so sensitive to touch that it's hard to make them without exploding prematurely. Therefore, direct production is strongly discouraged. With quantities of several grams there is already a risk of losing a finger or hand. Such accidents in the laboratories of amateur chemists have occurred again and again in the past, with ignorance about the potential danger and the existing laws playing the decisive role. The material is very difficult to handle: When the explosives were first manufactured at the end of the 19th century, several workers were killed on the very first day.
  
The conduct of experiments with explosives in schools is severely limited due to the potential danger and the existing laws. The pupils' attention is drawn to the fact that the acquisition, production and storage of explosives and pyrotechnic articles are subject to authorization. The handling of explosives is regulated by law, the private manufacture of explosives and fireworks is prohibited under current law. For demonstrations with explosives, one will have to resort to films in most cases. The experiment described earlier for the production of Flash powder made from potassium permanganate and magnesium powder is no longer recommended for schools today. Toxic by-products are created. Such mixtures have long been used as a light source in photography.
 
 
 
Potassium permanganate reacts violently with magnesium powder.
 
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The production and burning of black powder is not as problematic as the production of other explosives, but the use of a film is also recommended here. Black powder is not as sensitive to friction, so it is easier to handle. However, a static spark can ignite it, for example when the skin rubs against clothing. Burning it down in a closed container is very dangerous, as a large overpressure builds up here. Information on the history of gunpowder can be found in the chemical portrait of potassium nitrate.
 
 
 
 
Black powder burns with a large jet flame.
 
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While small amounts of black powder burn off relatively slowly with the formation of large amounts of gas, chlorate explosives such as chloratite 3 burn at ten times the speed. The bang in a New Year's Eve is not created by the burning of the black powder, but by the cramped paper container that prevents the gases from spreading, creating overpressure and a shock wave. Black powder explodes with a bang from a quantity of about one kilogram. In the case of a stronger explosive, it bangs even without a container, since the resulting shock wave exceeds the speed of sound even without a container. The graph compares the detonation speed of known explosives.
  
 
 
 
One of the most powerful known explosives is the hexanitro-isowurtzitane CL20, discovered in 1990, which detonates at 9.38 kilometers per second. This corresponds to about thirty times the speed of sound. Some explosives, such as the TNT contained in grenades and bombs or the dynamite invented by Alfred Nobel, can be stored relatively safely, you can even throw them into the fire without them exploding. The ignition is on Initial explosive like lead azide and a secondary ignition charge with Nitropenta necessary. Today detonation fuses with electronic control and a high safety standard are used in mining or when demolishing buildings.




This dummy comes from an old showcase:
Ammon-Gelit with detonation fuse and fuse alone.


TNT is toxic and dangerous to the environment. Ammunition scraps can contaminate the ground. In modern hand grenades of the German Federal Armed Forces, TNT is no longer used, but around 60 grams of nitropenta. Octogen is part of the air-firing or impact-firing rifle grenades. When plasticizing hexogen with a wax or a modeling clay, you get the Plastic explosives C4, which is absolutely safe to use. Semtex is a highly explosive plastic explosive that contains hexogen and nitropenta. Explosives based on ammonium nitrate are also considered to be relatively safe to handle. They are mainly used in mining. A binary explosive like Tannerite consists of two components like ammonium nitrate and an additive. Both are mixed just before ignition.



 
When lead azide detonates, a pressure wave is created.

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Under one explosion one generally understands a chemical reaction that is associated with a pressure wave. A Deflagration is a slow explosion: the burning speed is no more than one meter per second. If the burning speed is over one meter per second and the speed of sound is not exceeded, then it is a question of one Deflagration. At a Detonation if the speed of sound is exceeded, a very high pressure of up to 500 kilobars builds up at the same time. In such a pressure wave, the entire explosive explodes in one fell swoop. Objects immediately next to it can be completely destroyed and pulverized. Detonate TNT or Nitropenta. At a implosion a sudden negative pressure arises, the destructive effect is achieved by the effect of the external air pressure on the interior with the negative pressure. An implosion can occur, for example, if a gasoline tank burns, which is extinguished with cold water and the remaining gasoline vapors in the tank quickly condense due to the cooling.
 
 

 
This sleeve was dented after an implosion.
 
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Nowhere does the ambivalence of chemical-technical inventions come into their own as with explosives. They are useful in road construction or mining, in targeted building demolition or in the airbag in motor vehicles. In weapons they are used against material targets or against people.

in the Airbag for motor vehicles, a gas is released in a fraction of a second, which then inflates a sack that provides protection for the driver in the event of an impact. Pyrotechnic gas generators use a tablet which, after ignition, presses a hot gas through a metal filter into the airbag. Sodium azide or a mixture of sodium nitrate and amorphous boron, which can be made to explode with the help of lead azide, was used in the past. Instead of boron, 5-aminotetrazole is also suitable. This creates large amounts of nitrogen that inflate the airbag in the event of an accident. The igniter tablets in newer airbags do not use lead or sodium azide; they contain, for example, gun cotton and nitroglycerin or a mixture of citric acid and a chlorate. In cold gas generators, a helium-argon mixture is kept in a small container under pressure and released with an explosive when triggered.
 
The traditional explosives are significantly surpassed by arrangements with an implosion effect: In thermobaric weapons nanoscale fuels are finely divided in the air and ignited. For example, isopropyl nitrate and magnesium powder are used. The effect corresponds to that of an aerosol bomb: the fuel is first finely distributed and then ignites together with the air. The rapid reaction with the oxygen in the air and, in some cases, with the nitrogen in the air, first creates a large ball of fire and then the sudden cooling of the reaction gas creates a negative pressure. The resulting implosion depresses buildings, bunkers and cellars. People are also killed by the extreme pressure differences. Due to their far-reaching and extremely destructive effects, thermobaric weapons represent a border area between conventional weapons and weapons of mass destruction. New, internationally valid agreements must be made here.
 
In a Railgun projectiles are accelerated to many times the speed of sound with the help of electrical energy. The effect of such a projectile unfolds on impact: the energy can considerably exceed the effect of a warhead. Ammunition with explosives then no longer has to be stored on a ship, for example, but a railgun requires large electrical battery systems to operate.