The Chemistry of War: Non Lethal Weapons Tear Gas

an entry by Mika Thomas, Helen Sakharova, Ko Cheng Chan

navy gas.jpg

Figure 1: A Us soldier wearing a gas mask while traveling through a field filled with tear gas during a training drill

The human body is wonderfully capable of quickly responding to its environment.  Different substances trigger different reaction in the human body.  Tear gas, or a lachrymator, is a substance that interacts violently with the mucosal membranes such as the eyes, mouth, nose and lungs.  Tear gas is actually not a gas, but a colloid, more specifically, an aerosol.  The chemical structure of tear gas is what causes it to affect us differently than other substances.

    Pepper spray also applies to the definition of a tear gas however, unlike CN gas, it is considered an inflammatory agent.  Pepper spray causes painful swelling of capillaries in the eyes and caused temporary blindness.   Pepper spray is relatively simple compared to CN and CS gases.  As the name would suggest, it is derived from peppers.  Peppers contain a group of chemicals called capsaicin.  Pepper spray is also referred to as OC spray, Oleoresin Capsicum spray.  A capsaicin is a colorless irritating phenolic amide C18H27NO3  and is responsible for giving peppers their pungent spicy flavor.  Capsaicins’ molecular structure enable them to bind directly with proteins found in the membranes of pain sensing neurons.   This causes a victim to feel an intense burning sensation, excess salivation, excess mucous production, and even vomiting.  Therefore, pepper spray should be used wisely.   The difference between sweet peppers and the infamously painful ghost pepper is the concentration of capsaicin that they both contain.

This concept of concentration also plays strongly into the potency of pepper sprays and tear gases.  Different states have different laws on the limit of capsaicin that can be used for personal protection.  Even so, for almost all pepper sprays, a 1 second blast can render a person incapacitated for fifteen minutes to an hour. Different brands of pepper spray contain different amounts of solvents such as alcohols, and water.   The more dilute the concentration of capsaicin, the less potent the spray will be.  Like other forms of tear gas, pepper spray is canned under extremely high pressures and this results in an average can of pepper spray having a shooting range of about 10 feet.  More application differences between CN gas and pepper spray can be read about here.chem chem.png

Figure 2 : an image of a molecule of capsaicin.  The black balls represent carbon atoms, the white balls represent hydrogen atoms, the blue ball represents an atom of nitrogen and the red balls represent oxygen atoms.

    Tear gas is qualified as a nonlethal weapon, but there are serious risks involved.  Tear gases qualify as a type of chemical warfare and are prohibited in war by many international warfare treaties.  However, tear gases are allowed to be used by branches of the military for training.  Tear gases are use used normally for domestic riot control or personal protection.    CN (chloroacetophenone) gas, CS (chlorobenzylidenemalononitrile)) gas and bromoacetone are the types of tear gases used by law enforcement.  A familiar form of CN gas is Mace, a popular trademark brand of CN gas sold for personal protection.

    CS gas is normally composed of a white powder mixed in a dispersal agent like methylene chloride. At standard temperature and pressure, CS forms a white crystal with a low vapour pressure and poor solubility.  CS crystals are converted into microparticulate clouds by pyrotechnic devices.  CS gas may seem to be a continuous solution or a gas, but it is also a colloid.

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Figure 3: An image of a Us soldier wearing a gas mask to avoid the painful, yet temporary effects of CS gas. CS gas appears to be a white gas, but it is composed of small particles of white solid.

    As a result, CS gas is usually stored in cans at high pressures. A can of CS contains a gas and skin irritating solvents. When this can is used, highly pressurized gas escapes a can and the gas carries ultra-fine particles of CS.  The powdered CS becomes attached to the mucous membranes of organisms. The physical effects of CS gas is felt almost immediately.  A person’s breathing rate slows and excessive use of CS gas can lead to death. The poor solubility of CS makes it that it can exist on a mucous membrane for a long period of time if not physically removed.  Luckily, wind and fresh air can removed CS particles from the skin.  Gas masks work by protecting ones mucous membranes.

    Because it has been dubbed a nonlethal weapon there is fear that authoritative forces use it too liberally.    Tear gas is technically a “less-than-lethal” weapon because it can, in some cases, lead to death.  There is controversy over allowing authoritative forces to use tear gas.  Often, law enforcers must be exposed to tear gas themselves before they gain the right to use it.  While the memory f the pain of peppery spray might stop a young officer from using it too much, an older officer might not remember the pain and use it too often.  CN gas is excruciatingly painful and is often used on protesters as shown below.  The use of tear gas has raised social controversy that has even inspired for scientific research to be conducted on tear gases.  chem riot.jpg

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The Chemistry of War: Nuclear Bombs

By Helen Sakharova, Mika Thomas, and Ko Cheng Chan

In modern warfare, explosives are used all the time. They destroy bridges and barricades, stop armored vehicles in their tracks, and bury enemies in their own tunnels. But the most terrifying weapon ever invented by humans, the nuclear bomb, is on a different level entirely. Here is a weapon that can level a city with a single strike. Enough of them could even destroy the world. Yet a nuclear bomb, from a blinding explosion to a billowing mushroom cloud, is just a particularly deadly manifestation of chemistry. Lets start with the basics.

Fission

The first nuclear bombs, including the ones detonated over Hiroshima and Nagasaki, were fission bombs. They utilized uranium or plutonium, large, heavy elements that can undergo chain fission reactions. Fission is when a large nucleus falls apart into smaller nuclei, releasing neutrons and gamma rays in the process. In a chain reaction, the newly released neutrons strike the nuclei of other atoms, which then undergo fission as well, releasing even more neutrons. This cascade of fission reactions results in the huge release of energy accompanied by the explosion of an atomic bomb.

The kinetics of a chain fission reaction are particularly interesting to observe. Chain fission reactions don’t really have a “rate”, since the size of the reaction increases exponentially over time, assuming the reaction is sustained. It is necessary to note that not all of the neutrons necessarily cause further fission reactions: they may simply escape the system as a whole. They can also be captured without causing another fission reaction. If not enough neutrons cause secondary fission reactions, the number of reacting atoms decreases over time and the chain reaction sputters out. Thus, the number of fission reactions in progress, i.e. the size of the reaction, at a certain point in time can be determined by the formulae^{(k-1)t/\Lambda}. Here, Λ is the mean generation time, or the average time it takes for a newly released neuton to be “captured” by another nucleus and cause a fission reaction. As you can probably see, whether or not the chain reaction will be able to sustain itself or not depends on k, the effective neutron multiplication factor. If k is less than one, the system is subcritical, and any spontaneous or intentional fission reaction that occurs will quickly grow weaker and stop. If k is one, the system is critical, and any fission reactions will continue at a constant rate. Nuclear power plants operate at the critical point, since the constant fission reactions provide a steady source of energy. However, if k is greater than one, the system becomes supercritical. In this case, the reaction will get faster, and faster, and faster, accelerating exponentially until it spirals out of control and becomes a nuclear explosion.

This is the fission reaction of Uranium 235. Note how the chain reaction leads to exponentially more reactions taking place.

Fusion

The most powerful bomb ever detonated was the Tsar Bomba, a thermonuclear bomb that generated over 210 petajoules of energy, the equivalent of 50 million tons of TNT. Like all thermonuclear weapons, the Tsar Bomba utilized fusion. Nuclear fusion is the opposite of fission.  Nuclear fusion is the process where two light elements (elements with low atomic numbers) are fused together, forming a new nucleus and releasing a lot of energy.

At first glance, this seems illogical. How can forcing two atoms together possibly release energy? Wouldn’t the positive charges of the nuclei repel each other at close range? Indeed they do. However, at extremely close ranges, we encounter a force seldom mentioned in chemistry: the nuclear force. The nuclear force is the attractive force between two nucleons (neutrons or protons). By forcing two nuclei close enough together, this attractive force overcomes the repulsion between the protons and the nuclei join together. At this point, some of the mass is directly converted into photons, or energy. The exact amount of energy created strictly relates to the change in mass according to the equation E=Δmc2. Even though only tiny amounts of mass are lost, relatively large amounts of energy are produced.

Here is a video from CrashCourse explaining nuclear fusion.

The Hydrogen Bomb

Hydrogen bombs, or thermonuclear weapons, utilize both fission and fusion to cause the most powerful explosions ever created by humans. Inside the casing, a thermonuclear warhead of the typical Teller-Ulam design basically carries two bombs encased in polystyrene foam. The first is a fission bomb which releases large amounts of X-rays and gamma rays that are reflected off the inside of the casing back into the polystyrene foam. The irradiated polystyrene foam then becomes a plasma. This plasma compresses the second bomb, which consists of fusion fuel encased in uranium with a fissile spark plug inside. The compression from the plasma sets off a fission reaction in the spark plug, which pushes against the fusion fuel. Compressed from both sides and heated to extreme temperatures, the fuel, lithium-6 deuteride, produces tritium, which sets off a fusion reaction between the tritium and deuterium.

Step-by-step explosion of a hydrogen bomb. The arrows symbolize x-rays and gamma rays.

Chemistry of War: Stun Guns and Tasers

Continuing the topic of items used to incapacitate the enemy without killing them is with electricity rather than chemically. However, the proper functioning of a Taser is a direct result of the chemical properties of its materialistic components.  The word Taser and stun gun are used interchangeably. However, there are different types of stun guns or Tasers.  Some Tasers utilize properties of projectiles and therefore are more suited when an attacker is out of a victim’s arm reach. Taser is more often used for these types since it is actually an acronym for “Tomas A. Swift’s Electric Rifle”.

A typical Taser requires a 9 volt battery but the Tase Chemistry of War: Stun Guns and Tasers

The proper functioning of a Taser is a direct result of the chemical properties of its materialistic components.  The word Taser and stun gun are often used interchangeably.  However, there are different types of stun guns or Tasers.  Some Tasers utilize properties of projectiles and therefore are more suited when an attacker is out of a victim’s arm reach. Taser is the more commonly used word for these weapons. The word Taser is actually an acronym for “Thomas A. Swift’s Electric Rifle”.

A typical Taser requires a 9 volt battery but the Taser itself is still labeled as several 100kV. The increase in voltage is due to amplifiers and transformers in the Taser’s housing.  A battery is a cell that can convert stored chemical energy into useful energy. The amount of energy is calculated through two types of equations: reduction and oxidation. Reduction consists of an atom gaining electrons and oxidation is an atom losing electrons. Together the transfer of electrons produces a current. Tasers are able to have high voltages through the help of transformers to amplify the low 9 volts but voltages as high as 100kV.  However 100kV is not needed in most cases of authoritative force.

Common lithium battery is made up of -LiCO2(Lithium Cobalt Oxide) and LiC6

The reduction potential equations are:

Li+ +C6 +e– = LiC6      CoO2 + Li+ + e = LiCoO2

A high voltage does not determine how much damage a Taser can do.  Instead, it depends on the amount of current.

Tasers are effective in incapacitating the target by forcing their muscles to contract and release rapidly, causing twitching and convulsions. The human body is controlled by the brain through the use of electrical signals.  An electrical impulse can cause a muscle or group of muscles to contract or expand as necessary.  A Taser injects a foreign electrical impulse into the body and this debilitates a person temporarily (for as long as the Taser is being implemented). The act of a Taser’s current entering a human body is a result of the electron flow.  A Taser includes two parallel electrodes and two smaller test electrodes as shown in the diagram below.  When someone thinks about a Taser, the small test electrodes are probably what their minds first refer to.

As seen in the diagram, the battery offers a current that is amplified by the transformers found in the amplifier circuit.  Near the end of the Taser there are two parallel electrodes, a positively charged electrode and a negatively charged one.  These electrodes are made from a conductive metal plate.  Since these electrodes are placed along the curcuit, there is a high voltage difference between them.  Electrons want to flow between these electrodes, but they are placed too far apart, there is a gap in the circuit.  In comparison, the test electrodes are much closer together.  These smaller electrodes are used by the Taser wielder to see if the Taser is functioning.  If current is flowing through the Taser, then a small bluish, spark will jump between the test electrodes. The crackling spark is composed of air atoms that have been ionized by the electrical energy derived from the battery.  This noisy bright, crackling spark is an image that is normally associated with Tasers.  The parallel electrodes are two far apart to create a such a spark.  A Taser can inflict temporary damage on a person if their body is used to complete the circuit, or to fill the circuit gap between the two main electrodes.  Due to the potential difference in these electrodes, if a conductive object is placed between them, a large current flows.

 Additionally, there are flying Tasers that also use electrodes and a 9 volt batteries.  The main difference in the flying Taser is shown by the diagram below.  The electrodes fly out of the Taser as a projectile.  The electrodes are launched when the trigger is pulled.  The trigger opens a compressed gas cartridge and the electrodes are launched towards an attacker.

 The main risk in using a taser is found when it is used on someone who has heart complications.   Like any other muscle in the body, the heart contracts and expands due to electrical impulses, and a taser interferes with those interactions.  If someone has a weak heart, it is possible for them to die after being tased.  Tasers are weapons and, especially when used near water, can be lethal.  In 2010 a man in Hempstead died after being tased while wearing rain drenched clothing.

Due to the risk of Tasers, authoritative figures are required to use Tasers responsibly.  Here is an article describing how the some departments of the military are beginning to increase their use of Tasers. There is also a branch of authority called the Military Police.  Members of the Military police enforce the laws and regulations of the military.  In order to enforce such regulations members of the Military Police use nonlethal weaponry such as Tasers.  However, in order to encourage humane usage, military police officers are required to be hit with a Taser so they understand

Figure 5:  A picture of a military police officer being hit with a flying Taser gun.  This must be endured in order to earn the authority

r itself is still labeled as several 100kV. A battery is a cell that can convert stored chemical energy into useful energy. The amount of energy is calculated through two types of equations: reduction and oxidation. Reduction consists of an atom gaining electrons and oxidation is an atom losing electrons. Together the transfer of electrons produce a current. Tasers are able to have high voltages through the help of transformers to amplify the low 9 volts but voltages as high as 100kV are not needed in most cases.

Common lithium battery is made up of -LiCO2(Lithium Cobalt Oxide) and LiC6

The reduction potential equations are:

Li+ +C6 +e– = LiC6      CoO2 + Li+ + e = LiCoO2

Tasers function through two launching two prongs into the target. The farther apart the two prongs are, the more voltage is needed to complete the circuit. However a high voltage does not determine how much damage it does, instead it depends on the amount of current. Contact stun guns do not need a large voltage since the distance between the charge electrodes is fixed.

Tasers are effective in incapacitating the target by forcing their muscles to contract and release rapidly, causing twitching and convulsions. The human body is controlled by the brain through the use of electrical signals.  An electrical impulse can cause a muscle or group of muscles to contract or expand as necessary.  A Taser injects a foreign electrical impulses into the body and this debilitates a person temporarily (for as long as the Taser is being implemented). The act of a Taser’s current entering a human body is a result of the electron flow.  A Taser includes two electrodes and two smaller test electrodes as shown in the diagram below.  When someone thinks about a Taser, the small test electrodes are probably what their minds first refer to.

As seen in the diagram, the battery offers a current that is amplified by the transformers found in the amplifier circuit.  Near the end of the Taser there are two parallel electrodes a positively charged electrode and a negatively charged one.  These electrodes are made from a conductive metal plate.  Since these electrodes are placed along the surface, there is a high voltage difference between them.  Electrons want to flow between these electrodes, but they are placed too far apart, there is a gap in the circuit.  In comparison, the test electrodes are much closer together.  These smaller electrodes are used by the Taser wielder to see if the Taser is functioning.  If current is flowing through the Taser, then a small bluish, spark will jump between the test electrodes. The crackling spark is composed of air atoms that have been ionized by the electrical energy derived from the battery.  This crackling spark is an image that is normally associated with Tasers.  The parallel electrodes are two far apart to create a spark.  A Taser can inflict temporary damage on a person if their body is used to fill the circuit gap between the two main electrodes.  Due to the potential difference in these electrodes if a conductive object is placed between them, a large current flows.

Additionally, there are flying Tasers that also use electrodes and a 9 volt battery.  The main difference in the flying Taser is sown by the diagram below.  The electrodes fly out of the Taser as a projectile.  The electrodes are launched when the trigger is pulled.  The trigger opens a compressed gas cartridge and the electrodes are launched towards an attacker.

The main risk in using a stun gun is if the target already had heart problems and the shock is applied near the chest which can lead to cardiac arrest and/or death.

Here is an article of the military more recently starting to use stun guns. There is also a branch of authority called the Military Police.  Members of the Military police enforce the laws and regulations of the military.  In order to enforce such regulations members of the Military Police use nonlethal weaponry such as Tasers.  However, in order to encourage humane usage, military police officers are required to be hit with a Taser so they understand.

The Chemistry of War: Chemical Explosives

In the modern world, chemistry is all around us. One of the most spectacular, and most terrifying, uses of chemistry is on the battlefield. Chemistry, in the form of artillery and explosions, can turn whole cities into fields of rubble in a matter of hours, or, in the case of a nuclear bomb, in an instant. The science of military explosives is a fascinating one, so lets begin with the basics, starting with conventional chemical explosives.

Chemical Explosions: The Basics

Chemical explosives are substances that, when exposed to heat or shock, rapidly decompose, releasing large amounts of gas and heat. The most important thing about an explosive reaction is that it is fast. Any combustion reaction, such as the combustion of gasoline, releases relatively large amounts of gas and heat. In fact, most fuels have a higher specific energy (energy stored per unit of volume) than explosives. Burning a kilogram of gasoline produces about 46 MJ of energy, compared to the mere 4.6 MJ produced by detonating a kilogram of TNT. Yet a small package of TNT scares us a lot more than a bottle of gasoline. The answer to this apparent paradox is basic kinetics. The rate of reaction of exploding TNT is several thousand times faster than that of burning gasoline, making it infinitely more dangerous.

Not all reactions that rapidly create large amounts of gas are termed explosions. In order to truly be considered an explosion, the reaction must also be exothermic. One classic example is the reaction of nitrogen and oxygen gas to form NO. This reaction is spontaneous at temperatures greater than 2000 degrees Celsius, and produces gaseous products, but it is endothermic, absorbing 180 kJ per mole from its surroundings. Thus, it is not classified as an explosion.

A diagram of a molecule of TNT (trinitrobenzene). The white atoms represent hydrogen atoms, the black atoms represent carbons atoms, the red atoms represent oxygen atoms, and the blue atoms represent nitrogen atoms.

Detonation vs. Deflagration

Explosives can be divided into two categories: those that work by detonation and those that work by deflagration. Deflagration is basically just the fast, but subsonic, combustion of a material such as gunpowder. Explosives that work by deflagration are usually termed the “low explosives”. Detonation, on the other hand, occurs when an exothermic reaction accelerates through the material at supersonic speeds, creating a shock wave (an advancing area of extreme pressure) in front of it. These are the “high explosives”. Low explosives are easier to control, but are far less powerful.

The power of an explosion can be measured in its explosive velocity. This is the speed at which the reaction, and thus the shock wave, progresses through the material. Deflagration explosions also have an explosive velocity, though it is generally smaller than that of detonation ones. In fact, you can even measure the explosive velocity of a burning match! However, this is usually referred to as flame speed, since few people would refer to a lit match or a burning stove as an explosion. For example, the flame speed of methane in air is 1.3 ft/s, or around 0.4 m/s. Compare that to 6,900 m/s, the explosive velocity of TNT.

Types of explosives

A chemical explosive is usually either a pure, unstable compound, such as nitroglycerin or the RDX found in C-4, or a mix of oxidizer and fuel. The difference is primarily in the sort of reaction the explosive undergoes when it reacts. Most pure compound explosives work by dissociating when shocked, with each dissociating molecule shocking the next one into dissociating (this is what the above-mentioned shock wave is on a molecular level).

A mix of oxidizer and fuel is simply a highly explosive combustion reaction. One example of a fuel-and-oxidizer explosive is gunpowder. Typically gunpowder uses saltpeter, the oxidizer, charcoal, the fuel, and sulfur. The sulfur is optional since it only changes the reaction to reduce the amount of carbon monoxide produced. Using the fuel and oxidizer together provides a stable reaction that can be controlled. In fact, one does not even necessarily need the oxidizer. A combustion-based explosive that does not have any oxidizer is called a thermobaric explosive.

This is “The Father of all Bombs”, a nickname given to the most powerful non-nuclear bomb ever detonated. It was created by Russia and was tested in 2007. It is a thermobaric weapon with destructive power equivalent to 44 tons of TNT.

Thermobaric explosives

Thermobaric explosives are, barring nuclear bombs, the most destructive explosives ever created. Not only do thermobaric explosives create a vicious fireball that incinerates everything nearby, but the blast wave they produce is both stronger and lasts longer than that of a conventional explosive. Since they are completely reliant on oxygen from the air,  they can not function underwater, at high altitudes, or in adverse weather conditions. However, they are particularly effective at destroying tunnels and caves. This is because thermobaric weapons have one terrifying property. Upon detonation, they create large quantities of extremely hot gas. This gas then begins to cool with extreme rapidity. As we all know from the ideal gas law, this leads to an immediate drop in pressure, effectively creating a vacuum. Everything surrounding the explosion is sucked towards it. The effect in a tunnel is particularly devastating: even if those inside survive the initial fireball and shockwave, the resulting vacuum will suffocate them or simply rupture their lungs. This property of thermobaric weapons has given them the nickname “vacuum bombs”.