Amatol
Encyclopedia
- Not to be confused with the barbiturate Amytal.
Amatol is a highly explosive material
Explosive material
An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure...
made from a mixture of TNT and ammonium nitrate. Its name originates from the words ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
and toluene
Toluene
Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...
(a raw material of TNT). Amatol was used extensively during World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
and World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, typically as an explosive in military weapons such as aircraft bomb
Bomb
A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
s, shells
Shell (projectile)
A shell is a payload-carrying projectile, which, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot . Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used...
, depth charge
Depth charge
A depth charge is an anti-submarine warfare weapon intended to destroy or cripple a target submarine by the shock of exploding near it. Most use explosives and a fuze set to go off at a preselected depth in the ocean. Depth charges can be dropped by either surface ships, patrol aircraft, or from...
s and naval mine
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...
s.It was eventually replaced with alternative explosives such as Composition B
Composition B
Composition B, colloquially "comp B", is an explosive consisting of castable mixtures of RDX and TNT. It is used as the main explosive filling in artillery projectiles, rockets, land mines, hand grenades, sticky bombs and various other munitions...
, torpex
Torpex
Torpex is a secondary explosive 50% more powerful than TNT by mass. Torpex is composed of 42% RDX, 40% TNT and 18% powdered aluminium. It was used in the Second World War from late 1942. The name is short for Torpedo Explosive', having been originally developed for use in torpedoes...
and tritonal
Tritonal
Tritonal is a mixture of 80% TNT and 20% aluminium powder, used in several types of ordnance such as air-dropped bombs. The aluminium improves the total heat output and hence impulse of the TNT - the length of time during which the blast wave is positive...
.
Manufacture and use
Amatol exploits the synergySynergy
Synergy may be defined as two or more things functioning together to produce a result not independently obtainable.The term synergy comes from the Greek word from , , meaning "working together".-Definitions and usages:...
between TNT and ammonium nitrate: TNT has a high explosive velocity
Explosive velocity
Explosive velocity, also known as detonation velocity or velocity of detonation , is the velocity at which the shock wave front travels through a detonated explosive. The data listed for a specific substance is usually a rough prediction based upon gas behavior theory , as in practice it is...
and good brisance
Brisance
Brisance is the shattering capability of an explosive. It is a measure of the rapidity with which an explosive develops its maximum pressure. The term originates from the French verb "briser", which means to break or shatter...
, but is comparatively expensive and complex to manufacture and is also deficient in oxygen. This oxygen deficiency can be seen from the black smoke residue from a pure TNT explosion. When compared to TNT, ammonium nitrate has a fairly low detonation velocity and correspondingly low brisance
Brisance
Brisance is the shattering capability of an explosive. It is a measure of the rapidity with which an explosive develops its maximum pressure. The term originates from the French verb "briser", which means to break or shatter...
, but is extremely cheap and easy to manufacture. More important, it contains a surplus of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
which TNT can use during detonation
Detonation
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...
. Depending on the ratio of ingredients used, amatol leaves a residue of white or grey smoke after detonation.
Amatol allowed existing supplies of TNT to be expanded considerably, with little reduction in the destructive power of the final product, so long as the amount of TNT in the mixture did not fall below 60%. These were highly attractive features during major wars, when there was an insatiable demand for high explosives.
The amatol production process is very simple, another reason why it was so popular during major conflicts: TNT is gently heated until it melts, acquiring the physical characteristics of a syrup. Then the correct weight ratio of powdered ammonium nitrate is added and mixed in. Whilst this mixture is still in a molten
Melting
Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...
state, it is poured into empty bomb casings and allowed to cool and solidify. However, the lowest grades of amatol could not be produced by casting molten TNT. Instead, flaked TNT was thoroughly mixed with powdered ammonium nitrate and then compressed or extruded.
The colour of amatol ranges from off-white to slightly yellow or pinkish brown, depending on the mixture used, and remains soft for long periods of storage. It is also hygroscopic, which complicates long-term storage. To prevent moisture problems, amatol charges were coated with a thin layer of pure molten TNT or alternatively bitumen. Long-term storage issues were rarely a problem during major conflicts because munitions charged with amatol were generally used soon after manufacture.
Amatol should not be stored in containers made from copper or brass, as it can form dangerous compounds. Pressed, it is relatively insensitive, but may be detonated by severe impact, whereas when cast, it is extremely insensitive. Primary explosives such as mercury fulminate
Mercury(II) fulminate
Mercury fulminate, or Hg2, is a primary explosive. It is highly sensitive to friction and shock. It is mainly used as a trigger for other explosives in percussion caps and blasting caps...
were often used as a detonator
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....
, in combination with an explosive booster
Explosive booster
An explosive booster acts as a bridge between a low energy explosive and a low sensitivity explosive such as TNT. It increases the explosive shockwave from an initiating explosive to the degree sufficient to detonate the secondary charge.Unlike C4 plastic explosive, not all explosives can be...
charge such as tetryl
Tetryl
2,4,6-Trinitrophenylmethylnitramine commonly referred to as tetryl is a sensitive explosive compound used to make detonators and explosive booster charges....
.
The explosive charges hidden in HMS Campbeltown
HMS Campbeltown (I42)
HMS Campbeltown was a "Town"-class destroyer of the Royal Navy during the Second World War. She was originally an American destroyer , and, like many other obsolescent U.S. Navy destroyers, she was transferred to the Royal Navy in 1940 as part of the Destroyers for Bases Agreement. Campbeltown...
during the St. Nazaire Raid
St. Nazaire Raid
The St Nazaire Raid or Operation Chariot was a successful British amphibious attack on the heavily defended Normandie dry dock at St Nazaire in German-occupied France during the Second World War. The operation was undertaken by the Royal Navy and British Commandos under the auspices of Combined...
of 1942 contained amatol. Additionally, the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
X class
X class submarine
The X class was a World War II midget submarine class built for the Royal Navy during 1943–44.Known individually as X-Craft, the vessels were designed to be towed to their intended area of operations by a full-size 'mother' submarine - - with a passage crew on board, the operational crew...
midget submarine
Midget submarine
A midget submarine is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to 6 or 8, with little or no on-board living accommodation...
s which planted explosive charges beneath the German battleship Tirpitz
German battleship Tirpitz
Tirpitz was the second of two s built for the German Kriegsmarine during World War II. Named after Grand Admiral Alfred von Tirpitz, the architect of the Imperial Navy, the ship was laid down at the Kriegsmarinewerft in Wilhelmshaven in November 1936 and launched two and a half years later in April...
in September 1943 used two "saddle charges" containing a total weight of four tons
Long ton
Long ton is the name for the unit called the "ton" in the avoirdupois or Imperial system of measurements, as used in the United Kingdom and several other Commonwealth countries. It has been mostly replaced by the tonne, and in the United States by the short ton...
of amatol. Warheads for the German V-1 flying bomb
V-1 flying bomb
The V-1 flying bomb, also known as the Buzz Bomb or Doodlebug, was an early pulse-jet-powered predecessor of the cruise missile....
and V-2 rocket
V-2 rocket
The V-2 rocket , technical name Aggregat-4 , was a ballistic missile that was developed at the beginning of the Second World War in Germany, specifically targeted at London and later Antwerp. The liquid-propellant rocket was the world's first long-range combat-ballistic missile and first known...
s also contained amatol.
A derivative of amatol is amatex
Amatex
Amatex is a military explosive consisting of 51% ammonium nitrate, 40% TNT, and 9% RDX....
, consisting of 51% ammonium nitrate, 40% TNT, and 9% RDX.
Ammonite
Amatol is rarely encountered today, except in legacy munitions or unexploded ordnanceUnexploded ordnance
Unexploded ordnance are explosive weapons that did not explode when they were employed and still pose a risk of detonation, potentially many decades after they were used or discarded.While "UXO" is widely and informally used, munitions and explosives of...
. However, a form of amatol still exists under a different name — ammonite. Ammonite is a civilian explosive, generally comprising a 20/80 mixture of TNT and ammonium nitrate. Typically, it is used for quarrying or mining
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
purposes. It is a popular civilian explosive in Eastern Europe
Eastern Europe
Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...
and China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
.
Because the proportion of TNT is significantly lower than in its military counterpart, ammonite has much less destructive power. However, given the particular purposes for which ammonite is used, this is not a problem. In general, a 30 kilogram charge of ammonite is roughly equivalent to 20 kilograms of TNT.