Powder explosives, or gunpowder (also known as black powder), is one of the earliest chemical explosives on record. Once widely used as a blasting agent and a propelling charge in guns, it’s now largely been replaced by more modern alternatives.
Although it’s believed gunpowder was invented by Chinese monks around the ninth century, it wasn’t until 1846 that the first explosives were made by Ascanio Sobrero. He treated glycerol with a mixture of nitric and sulphuric acid, which produced nitroglycerine.
Nitroglycerine is a liquid explosive that became one of the three primary ingredients of dynamite. The other two chemical ingredients are oxidisers and peroxide. Nitroglycerine explosives are 25 times faster and three times more energetic than gunpowder explosives, which are mainly composed of saltpetre (potassium nitrate), sulphur, and charcoal.
Read on to learn more about the chemical reactions involved in explosives, common types of explosives, and the potential dangers.
In this post:
What type of chemical reaction is an explosive?
Chemically speaking, anything that is combustible and sealed can explode if there is a sufficient amount of oxygen, an igniter, and the right temperature and pressure conditions. An explosion can either be unidirectional, such as the explosion that travels inside a gun barrel, or it can be omni-directional, like a grenade explosion.
An explosion is essentially a very rapid oxidation reaction that produces a large amount of gas, resulting in a sudden release of pressure. To build extreme pressure (and thereby rapidly form gases), an explosive must be contained in a sealed vessel. Because the gases don’t have sufficient time to expand and thus dissipate the pressure and heat, they release tremendous energy in a relatively confined space. It’s this release that creates the explosion.
What two elements can make an explosion?
Several different elements can make an explosion. Hydrogen is one example, but any element that can rapidly react with oxygen in a sealed container is capable of causing an explosion.
And then there are the alkaline earth metals and alkali metals. They’re too unstable to exist as elements, but they can violently react with water, oxygen, and halogen. If the reactions are contained in a sealed container, they can also create explosions.
Essentially, you’ll need an element with relatively low electronegativity and an oxidising element with high electronegativity, like fluorine, to create an explosive reaction. In many cases, you’ll also require a catalyst.
Common types of explosives
Chemical-based explosives have various applications. The entertainment sector, for example, relies on explosives for fireworks and to create movie pyrotechnic special effects. They’re also used to demolish old and condemned buildings. In the mining industry, explosives are used to dislodge large chunks of ore rocks for processing.
In fact, some large sculptures and national landmarks, like Mount Rushmore in the US, wouldn’t have been possible without the use of explosives. However, while there are many productive uses for explosives, they’re also obviously frequently used as weapons.
Some of the most common types of explosives are the following:
- Trinitrotoluene (TNT)
- Nitrocellulose (guncotton, pyrocotton, nitrocotton)
- Emulsion and slurry explosives
These explosives typically require some kind of trigger (a primer, blasting cap or electric spark), a catalyst, and an oxidiser to work. The explosives themselves must be packed in a certain way to maximise the blast.
Some explosives, particularly those used in controlled demolitions, have delayed triggers to enable successive explosions with microsecond precision. This allows experts to manage the collapse of dilapidated buildings in a safe manner. For example, a skyscraper that’s surrounded by other buildings can be imploded to collapse vertically instead of radially or on its sides.
Explosive devices can’t react fast enough with oxygen in the air to create a very strong blast from their container. This means they need built-in oxidisers that can rapidly combine with the combustible chemicals of an explosive.
These oxidisers are typically inorganic compounds that have oxygen or other oxidising agents. Some examples of oxidisers include:
Nitroglycerin, otherwise known as 1,2,3-trinitroxypropane, is the explosive material found in dynamite.
It’s a colourless and odourless oily liquid that’s prepared by treating glycerol with nitric acid to form nitric acid ester. Nitroglycerin has the chemical formula C3H5N3O9 and the following molecular structure:
A peroxide is a compound that contains two atoms of oxygen per molecule. It has the general formula R−O−O−R. Peroxide is relatively unstable and easily releases extra oxygen, making it an ideal oxidising agent for explosives.
The most common type of peroxide with a wide range of uses is hydrogen peroxide (H2O2). Other examples of peroxides include:
- Barium peroxide (BaO2)
- Sodium peroxide (Na2O2)
- Zinc peroxide (ZnO2)
The dangers of explosives
It goes without saying that explosives are extremely dangerous – they can kill people and destroy properties in an instant. That being said, they can be stored, handled, transported, and used safely if the correct protocols are followed and the appropriate safety gear is worn.
Some explosives are designed to be stable as long as the components aren’t assembled.
For example, C-4 explosives are highly stable under a wide range of conditions. They can’t be detonated by simply dropping it or shooting a bullet at it. It won’t even explode when exposed to fire or microwaves. The only way you can only detonate C-4 is by a shockwave, which is created by firing a detonator that’s been inserted into it.
However, many types of explosives pose hazards before and after they are detonated. Some of the dangers of explosives are explored below.
1. Hazardous dust and debris
An explosion, such as the controlled demolition of a building, produces an enormous amount of hazardous dust and debris that can harm workers and bystanders. For example, inhaling fine grains of powdered concrete can cause breathing problems and potentially damage the alveoli and mucous membranes in our lungs.
Larger debris can injure people if it’s ejected outward from the centre of the explosion. This is the reason why nets and other safety barriers are installed around the demolition site.
2. Fire or malfunctioned explosions
Explosions involve high temperatures that can ignite combustible materials such as fossil fuels, dry leaves, wooden houses, and even trees. On the other hand, if an explosive malfunctions and does not detonate, it must be forced to explode at a safe distance to avoid accidental detonation when least expected.
3. Contaminated airborne particles
There’s always the danger of contaminated airborne particles following an explosion. Many old buildings, for instance, still contain asbestos insulation. The carcinogenic asbestos particles can potentially be inhaled, which can lead to cancer or a serious lung condition known as asbestosis.
Other contaminants, such as radioactive materials and toxic chemicals, can also mix with the air within the vicinity of the explosion. Again, breathing in these particles can cause a variety of serious health problems and even death.
There are different types of explosives but they tend to follow the same chemical reaction. An explosion can happen when a large amount of pressurised gas is suddenly released. Certain types of explosives also require a trigger, a catalyst, and an oxidiser to work. Some of the dangers of powder explosives include hazardous dust, debris, fire and contaminated airborne particles. It’s therefore essential to follow the proper protocols when storing, transporting, handling, and using explosives.
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