Explosive material

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This article is about chemical explosives. For album by Bond, see Explosive: The Best of Bond.

A number of 1.25lb M112 Demolition Charges, consisting of a C-4 compound, sit atop degraded weaponry scheduled for destruction

An explosive material is a substance that contains a great amount of stored energy that can produce a sudden expansion of the material after initiation, usually accompanied by the production of light, heat, and pressure. This event is called the explosion. An explosive charge is a measured quantity of explosive material.

The energy stored in an explosive material may be

chemical energy, such as nitroglycerine or grain dust
pressurized compressed gas, such as a gas cylinder or aerosol can
nuclear, such as fissile isotopes of uranium-235 and plutonium-239

[edit] Type of Reaction

There are different reasons and conditions that make a material explosive. Explosive material is often classified by the type of reaction that takes place.

[edit] Chemical

Chemical explosives are substances that contain a large amount of energy stored in chemical bonds.

Explosives are classified as low or high explosives according to their rates of burn: low explosives burn rapidly (or deflagrate), while high explosives detonate. While these definitions are distinct, the problem of precisely measuring rapid decomposition makes practical classification of explosives difficult.

[edit] Decomposition

The chemical decomposition of an explosive may take years, days, hours, or a fraction of a second. The slower processes of decomposition take place in storage and are of interest only from a stability standpoint. Of more interest are the two rapid forms of decomposition, deflagration and detonation.

[edit] Deflagration

Main article: Deflagration

In deflagration, the decomposition of the explosive material is propagated by a flame front, which moves slowly through the explosive material in contrast to detonation. Deflagration is acharacteristic of low explosive material.

[edit] Detonation

Main article: Detonation

The latter term is used to describe an explosive phenomenon whereby the decomposition is propagated by the explosive shockwave traversing the explosive material. The shockwave front is capable of passing through the high explosive material at great speeds, typically thousands of meters per second.

[edit] Mechanical

[edit] Exotic

In addition to chemical explosives, there exist varieties of more exotic explosive material, and theoretical methods of causing explosions. Examples include nuclear explosives, antimatter, and abruptly heating a substance to a plasma state with a high-intensity laser or electric arc.

[edit] Properties of Explosive Materials

To determine the suitability of an explosive substance for a particular use, its physical properties must first be investigated. The usefulness of an explosive can only be appreciated when the properties and the factors affecting them are fully understood. Some of the more important characteristics are discussed below:

[edit] Availability and Cost

Availability and cost of explosives is determined by the availability of the raw materials and the cost, complexity, and safety of the manufacturing operations.

[edit] Sensitivity

Main article: Sensitivity (explosives)

Regarding an explosive, this refers to the ease with which it can be ignited or detonated—i.e., the amount and intensity of shock, friction, or heat that is required. When the term sensitivity is used, care must be taken to clarify what kind of sensitivity is under discussion. The relative sensitivity of a given explosive to impact may vary greatly from its sensitivity to friction or heat. Some of the test methods used to determine sensitivity are as follows:

Impact Sensitivity is expressed in terms of the distance through which a standard weight must be dropped to cause the material to explode.
Friction Sensitivity is expressed in terms of what occurs when a weighted pendulum scrapes across the material (snaps, crackles, ignites, and/or explodes).
Heat Sensitivity is expressed in terms of the temperature at which flashing or explosion of the material occurs.

Sensitivity is an important consideration in selecting an explosive for a particular purpose. The explosive in an armor-piercing projectile must be relatively insensitive, or the shock of impact would cause it to detonate before it penetrated to the point desired. The explosive lenses around nuclear charges are also designed to be highly insensitive, to minimize the risk of accidental detonation.

[edit] Sensitivity to initiation

Is the index of the capacity of the explosive to be initiated into detonation in a sustained manner. It is defined by the power of the detonator which is certain to prime the explosive to a sustained and continuous detonation. Reference is made to the Sellier-Bellot scale that consists of a series of 10 detonators, from n. 1 to n. 10, each of which corresponds to an increasing charge weight. In practice most of the explosives on the market today are sensitive to the n. 8 detonator, where the charge corresponds to 2 grams of fulminate of mercury.

[edit] Velocity of detonation

Is the velocity with which the reaction process propagates in the mass of the explosive. Most commercial mining explosives have detonation velocities ranging from 1800 Mps to 8000 Mps. Today, velocity of detonation can be measured with accuracy. Together with density it is an important element influencing the yield of the energy transmitted (for both, atmospheric overpressure and ground acceleration).

[edit] Stability

Main article: Chemical stability

Stability is the ability of an explosive to be stored without deterioration.

The following factors affect the stability of an explosive:

Chemical constitution. The very fact that some common chemical compounds can undergo explosion when heated indicates that there is something unstable in their structures. While no precise explanation has been developed for this, it is generally recognized that certain radical groups, nitrite (–NO₂), nitrate (–NO₃), and azide (–N₃), are intrinsically in a condition of internal strain. Increasing the strain by heating can cause a sudden disruption of the molecule and consequent explosion. In some cases, this condition of molecular instability is so great that decomposition takes place at ordinary temperatures.
Temperature of storage. The rate of decomposition of explosives increases at higher temperatures. All of the standard military explosives may be considered to have a high degree of stability at temperatures of -10 to +35 °C, but each has a high temperature at which the rate of decomposition rapidly accelerates and stability is reduced.As a rule of thumb, most explosives become dangerously unstable at temperatures exceeding 70 °C.
Exposure to the sun. If exposed to the ultraviolet rays of the sun, many explosive compounds that contain nitrogen groups will rapidly decompose, affecting their stability.
Electrical discharge. Electrostatic or spark sensitivity to initiation is common to a number of explosives. Static or other electrical discharge may be sufficient to inspire detonation under some circumstances. As a result, the safe handling of explosives and pyrotechnics almost always requires electrical grounding of the operator.

[edit] Power

Main article: Power (physics)

The term power or performance as applied to an explosive refers to its ability to do work. In practice it is defined as the explosive's ability to accomplish what is intended in the way of energy delivery (i.e., fragment projection, air blast, high-velocity jets, underwater shock and bubble energy, etc.). Explosive power or performance is evaluated by a tailored series of tests to assess the material for its intended use. Of the tests listed below, cylinder expansion and air-blast tests are common to most testing programs, and the others support specific applications.

Cylinder expansion test. A standard amount of explosive is loaded into a long hollow cylinder, usually of copper, and detonated at one end. Data is collected concerning the rate of radial expansion of the cylinder and maximum cylinder wall velocity. This also establishes the Gurney energy or 2E.
Cylinder fragmentation. A standard steel cylinder is loaded with explosive and detonated in a sawdust pit. The fragments are collected and the size distribution analyzed.
Detonation pressure (Chapman-Jouguet condition). Detonation pressure data derived from measurements of shock waves transmitted into water by the detonation of cylindrical explosive charges of a standard size.
Determination of critical diameter. This test establishes the minimum physical size a charge of a specific explosive must be to sustain its own detonation wave. The procedure involves the detonation of a series of charges of different diameters until difficulty in detonation wave propagation is observed.
Infinite-diameter detonation velocity. Detonation velocity is dependent on loading density (c), charge diameter, and grain size. The hydrodynamic theory of detonation used in predicting explosive phenomena does not include diameter of the charge, and therefore a detonation velocity, for an imaginary charge of Infinite diameter. This procedure requires a series of charges of the same density and physical structure, but different diameters, to be fired and the resulting detonation velocities extrapolated to predict the detonation velocity of a charge of infinite diameter.
Pressure versus scaled distance. A charge of specific size is detonated and its pressure effects measured at a standard distance. The values obtained are compared with that for TNT.
Impulse versus scaled distance. A charge of specific size is detonated and its impulse (the area under the pressure-time curve) measured versus distance. The results are tabulated and expressed in TNT equivalent.
Relative bubble energy (RBE). A 5- to 50 kg charge is detonated in water and piezoelectric gauges measure peak pressure, time constant, impulse, and energy.

The RBE may be defined as K_x 3

RBE = K_s

where K = bubble expansion period for experimental (x) or standard (s) charge.

[edit] Brisance

Main article: Brisance

[edit] Density

Density of loading refers to the mass of an explosive per unit volume. Several methods of loading are available, including pellet loading, cast loading, and press loading; the one used is determined by the characteristics of the explosive. Dependent upon the method employed, an average density of the loaded charge can be obtained that is within 80-99% of the theoretical maximum density of the explosive. High load density can reduce sensitivity by making the mass more resistant to internal friction. However, if density is increased to the extent that individual crystals are crushed, the explosive may become more sensitive. Increased load density also permits the use of more explosive, thereby increasing the power of the warhead. It is possible to compress an explosive beyond a point of sensitivity, known also as "dead-pressing," in which the material is no longer capable of being reliably initiated, if at all.

[edit] Volatility

Volatility is the readiness with which a substance vaporizes. Excessive volatility often results in the development of pressure within rounds of ammunition and separation of mixtures into their constituents. Volatility affects the chemical composition of the explosive such that a marked reduction in stability may occur, which results in an increase in the danger of handling.

[edit] Hygroscopicity and Water Resistance

The introduction of water into an explosive is highly undesirable since it reduces the sensitivity, strength, and velocity of detonation of the explosive. Hygroscopicity is used as a measure of a material's moisture-absorbing tendencies. Moisture affects explosives adversely by acting as an inert material that absorbs heat when vaporized, and by acting as a solvent medium that can cause undesired chemical reactions. Sensitivity, strength, and velocity of detonation are reduced by inert materials that reduce the continuity of the explosive mass. When the moisture content evaporates during detonation, cooling occurs, which reduces the temperature of reaction. Stability is also affected by the presence of moisture since moisture promotes decomposition of the explosive and, in addition, causes corrosion of the explosive's metal container.

Explosives considerably differ from one another as to their behavior in the presence of water. Gelatin dynamites containing nitroglycerine have a degree of water resistance. Explosives based on ammonium nitrate have little or no water resistance.

[edit] Toxicity

Due to their chemical structure, most explosives are toxic to some extent. Explosive product gases can also be toxic.

[edit] Explosive Train

Main article: Explosive train

Another property of explosive material is where it exists in the explosive train of the device or system.

[edit] Volume of products of explosion

Avogadro's law states that equal volumes of all gases under the same conditions of temperature and pressure contain the same number of molecules, that is, the molar volume of one gas is equal to the molar volume of any other gas. The molar volume of any gas at 0°C and under normal atmospheric pressure is very nearly 22.4 liters. Thus, considering the nitroglycerin reaction,

C₃H₅(NO₃)₃ → 3CO₂ + 2.5H₂O + 1.5N₂ + 0.25O₂

the explosion of one mole of nitroglycerin produces 3 moles of CO₂, 2.5 moles of H₂O, 1.5 moles of N₂, and 0.25 mole of O₂, all in the gaseous state. Since a molar volume is the volume of one mole of gas, one mole of nitroglycerin produces 3 + 2.5 + 1.5 + 0.25 = 7.25 molar volumes of gas; and these molar volumes at 0°C and atmospheric pressure form an actual volume of 7.25 × 22.4 = 162.4 liters of gas.

Based upon this simple beginning, it can be seen that the volume of the products of explosion can be predicted for any quantity of the explosive. Further, by employing Charles' Law for perfect gases, the volume of the products of explosion may also be calculated for any given temperature. This law states that at a constant pressure a perfect gas expands 1/273.15 of its volume at 0 °C, for each degree Celsius of rise in temperature.

Therefore, at 15 °C (288.15 kelvin) the molar volume of an ideal gas is

V₁₅ = 22.414 (288.15/273.15) = 23.64 liters per mole

Thus, at 15 °C the volume of gas produced by the explosive decomposition of one mole of nitroglycerin becomes

V = (23.64 l/mol)(7.25 mol) = 171.4 l

[edit] Explosive strength

Main article: Strength (explosive)

The potential of an explosive is the total work that can be performed by the gas resulting from its explosion, when expanded adiabatically from its original volume, until its pressure is reduced to atmospheric pressure and its temperature to 15 °C. The potential is therefore the total quantity of heat given off at constant volume when expressed in equivalent work units and is a measure of the strength of the explosive.

[edit] Oxygen balance (OB%)

Main article: Oxygen balance

Oxygen balance is an expression that is used to indicate the degree to which an explosive can be oxidized. If an explosive molecule contains just enough oxygen to convert all of its carbon to carbon dioxide, all of its hydrogen to water, and all of its metal to metal oxide with no excess, the molecule is said to have a zero oxygen balance. The molecule is said to have a positive oxygen balance if it contains more oxygen than is needed and a negative oxygen balance if it contains less oxygen than is needed. The sensitivity, strength, and brisance of an explosive are all somewhat dependent upon oxygen balance and tend to approach their maximums as oxygen balance approaches zero.

[edit] Chemical Composition

A chemical explosive may consist of either a chemically pure compound, such as nitroglycerin, or a mixture of an fuel and a oxidizer, such as black powder or grain dust and air.

[edit] Chemically pure compounds

Some chemical compounds are unstable in that, when shocked, they react, possibly to the point of detonation. Each molecule of the compound dissociates into two or more new molecules (generally gases) with the release of energy.

Nitroglycerin: A highly unstable and sensitive liquid.
Acetone peroxide: A very unstable white organic peroxide.
TNT: Yellow insensitive crystals that can be melted and cast without detonation.
Nitrocellulose: A nitrated polymer which can be a high or low explosive depending on nitration level and conditions.
RDX, PETN, HMX: Very powerful explosives which can be used pure or in plastic explosives.
- C-4 (or Composition C-4): An RDX plastic explosive plasticized to be adhesive and malleable.

The above compositions may describe the majority of the explosive material, but a practical explosive will often include small percentages of other materials. For example, dynamite is a mixture of highly sensitive nitroglycerin with sawdust, powdered silica, or most commonly diatomaceous earth, which act as stabilizers. Plastics and polymers may be added to bind powders of explosive compounds; waxes may be incorporated to make them safer to handle; aluminium powder may be introduced to increase total energy and blast effects. Explosive compounds are also often "alloyed": HMX or RDX powders may be mixed (typically by melt-casting) with TNT to form Octol or Cyclotol.

[edit] Mixture of oxidizer and fuel

An oxidizer is a pure substance (molecule) that in a chemical reaction can contribute some atoms of one or more oxidizing elements, in which the fuel component of the explosive burns. On the simplest level, the oxidizer may itself be an oxidizing element, such as gaseous or liquid oxygen.

Black powder: Potassium nitrate, charcoal and sulfur
Flash powder: Fine metal powder (usually aluminium or magnesium) and a strong oxidizer (e.g. potassium chlorate or perchlorate).
Ammonal: Ammonium nitrate and aluminium powder.
Armstrong's mixture: Potassium chlorate and red phosphorus. This is a very sensitive mixture. It is a primary high explosive in which sulfur is substituted for some or all phosphorus to slightly decrease sensitivity.
Sprengel explosives: A very general class incorporating any strong oxidizer and highly reactive fuel, although in practice the name most commonly was applied to mixtures of chlorates and nitroaromatics.
- ANFO: Ammonium nitrate and fuel oil.
- Cheddites: Chlorates or perchlorates and oil.
- Oxyliquits: Mixtures of organic materials and liquid oxygen.
- Panclastites: Mixtures of organic materials and dinitrogen tetroxide.

[edit] Classification of Explosive Materials

[edit] By Sensitivity

[edit] Primary Explosive

A primary explosive is an explosive that is extremely sensitive to stimuli such as impact, friction, heat, static electricity, or electromagnetic radiation. A relatively small amount of energy is required for initiation. As a very general rule, primary explosives are considered to be those compounds that are more sensitive than PETN. As a practical measure, primary explosives are sufficiently sensitive that they can be reliably initiated with a blow from a hammer; however, PETN can usually be initiated in this manner, so this is only a very broad guideline. Additionally, several compounds, such as nitrogen triiodide, are so sensitive that they cannot even be handled without detonating.

Primary explosives are often used in detonators or to trigger larger charges of less sensitive secondary explosives. primary explosives are commonly used in blasting caps to translate a signal (electrical, shock, or in the case of laser detonation systems, light) into an action, i.e., an explosion. A small quantity—usually milligrams—is sufficient to initiate a larger charge of explosive that is usually safer to handle.^[1]

Examples of primary high explosives are:

[edit] Secondary Explosive

A secondary explosive is less sensitive than a primary explosive and require substantially more energy to be initiated. Because they are less sensitive they are usable in a wider variety of applications and are safer to handle and store. Secondary explosives are used in larger quantities in an explosives train and are usually initiated by a smaller quanitity of a primary explosive.

Examples of secondary explosives include TNT and RDX.

[edit] By Velocity

[edit] Low explosives

Low explosives are compounds where the rate of decomposition proceeds through the material at less than the speed of sound. The decomposition is propagated by a flame front (deflagration) which travels much more slowly through the explosive material than a shock wave of a high explosive. Under normal conditions, low explosives undergo deflagration at rates that vary from a few centimeters per second to approximately 400 metres per second. It is possible for them to deflagrate very quickly, producing an effect similar to a detonation. This can happen under higher pressure or temperature, which usually occurs when ignited in a confined space.

A low explosive is usually a mixture of a combustible substance and an oxidant that decomposes rapidly (deflagration), however they burn slower than a high explosive which has an extremely fast burn rate.

Low explosives are normally employed as propellants. Included in this group are gun powders and pyrotechnics, such as flares.

[edit] High explosives

High explosives are explosives that detonate. They are normally are employed in mining, demolition, and military warheads. High explosive compounds detonate at rates ranging from 3,000 to 9,000 meters per second, and are, conventionally, subdivided into two explosives classes, differentiated by sensitivity:

[edit] By Composition

[edit] Priming Composition

Priming compositions are primary explosives mixed with other compositions to control (lessen) the sensitivity of the mixture to the desired property.

For example, primary explosives are so sensitive that they need to be stored and shipped in a wet state to prevent accidental initiation.

[edit] Shipping Label Classifications

Explosives warning sign

Shipping labels and tags will include UN and national, e.g. USDOT, hazardous material Class with Compatibility Letter, as follows:

1.1 Mass Explosion Hazard
1.2 Non-mass explosion, fragment-producing
1.3 Mass fire, minor blast or fragment hazard
1.4 Moderate fire, no blast or fragment: a consumer firework is 1.4G or 1.4S
1.5 Explosive substance, very insensitive (with a mass explosion hazard)
1.6 Explosive article, extremely insensitive

A Primary explosive substance (1.1A)

B An article containing a primary explosive substance and not containing two or more effective protective features. Some articles, such as detonator assemblies for blasting and primers, cap-type, are included. (1.1B, 1.2B, 1.4B)

C Propellant explosive substance or other deflagrating explosive substance or article containing such explosive substance (1.1C, 1.2C, 1.3C, 1.4C)

D Secondary detonating explosive substance or black powder or article containing a secondary detonating explosive substance, in each case without means of initiation and without a propelling charge, or article containing a primary explosive substance and containing two or more effective protective features. (1.1D, 1.2D, 1.4D, 1.5D)

E Article containing a secondary detonating explosive substance without means of initiation, with a propelling charge (other than one containing flammable liquid, gel or hypergolic liquid) (1.1E, 1.2E, 1.4E)

F containing a secondary detonating explosive substance with its means of initiation, with a propelling charge (other than one containing flammable liquid, gel or hypergolic liquid) or without a propelling charge (1.1F, 1.2F, 1.3F, 1.4F)

G Pyrotechnic substance or article containing a pyrotechnic substance, or article containing both an explosive substance and an illuminating, incendiary, tear-producing or smoke-producing substance (other than a water-activated article or one containing white phosphorus, phosphide or flammable liquid or gel or hypergolic liquid) (1.1G, 1.2G, 1.3G, 1.4G)

H Article containing both an explosive substance and white phosphorus (1.2H, 1.3H)

J Article containing both an explosive substance and flammable liquid or gel (1.1J, 1.2J, 1.3J)

K Article containing both an explosive substance and a toxic chemical agent (1.2K, 1.3K)

L Explosive substance or article containing an explosive substance and presenting a special risk (e.g., due to water-activation or presence of hypergolic liquids, phosphides or pyrophoric substances) needing isolation of each type (1.1L, 1.2L, 1.3L)

N Articles containing only extremely insensitive detonating substances (1.6N)

S Substance or article so packed or designed that any hazardous effects arising from accidental functioning are limited to the extent that they do not significantly hinder or prohibit fire fighting or other emergency response efforts in the immediate vicinity of the package (1.4S)

[edit] Legacy article contents

Contents below this heading have not been incorporated into the regrouped article.

[edit] Chemical Explosives

Explosives usually have less potential energy than petroleum fuels, but their high rate of energy release produces a great blast pressure. TNT has a detonation velocity of 6,940 m/s compared to 1,680 m/s for the detonation of a pentane-air mixture, and the 0.34-m/s stoichiometric flame speed of gasoline combustion in air.

The properties of the explosive indicate the class into which it falls. In some cases explosives can be made to fall into either class by the conditions under which they are initiated. In sufficiently large quantities, almost all low explosives can undergo a Deflagration to Detonation Transition (DDT). For convenience, low and high explosives may be differentiated by the shipping and storage classes.

[edit] Chemical explosive reaction

A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat. Many substances not ordinarily classed as explosives may do one, or even two, of these things. For example, at high temperatures (> 2000°C) a mixture of nitrogen and oxygen can be made to react with great rapidity and yield the gaseous product nitric oxide; yet the mixture is not an explosive since it does not evolve heat, but rather absorbs heat.

N₂ + O₂ → 2NO - 43,200 calories (or 180 kJ) per mole of N₂

For a chemical to be an explosive, it must exhibit all of the following:

Rapid expansion (i.e.,. rapid production of gases or rapid heating of surroundings)
Evolution of heat
Rapidity of reaction
Initiation of reaction

[edit] Sensitiser

A sensitiser is a powdered or fine particulate material that is sometimes used to create voids that aid in the initiation or propagation of the detonation wave. It may be as high-tech as glass beads or as simple as seeds.

[edit] Measurement of chemical explosive reaction

The development of new and improved types of ammunition requires a continuous program of research and development. Adoption of an explosive for a particular use is based upon both proving ground and service tests. Before these tests, however, preliminary estimates of the characteristics of the explosive are made. The principles of thermochemistry are applied for this process.

Thermochemistry is concerned with the changes in internal energy, principally as heat, in chemical reactions. An explosion consists of a series of reactions, highly exothermic, involving decomposition of the ingredients and recombination to form the products of explosion. Energy changes in explosive reactions are calculated either from known chemical laws or by analysis of the products.

For most common reactions, tables based on previous investigations permit rapid calculation of energy changes. Products of an explosive remaining in a closed calorimetric bomb (a constant-volume explosion) after cooling the bomb back to room temperature and pressure are rarely those present at the instant of maximum temperature and pressure. Since only the final products may be analyzed conveniently, indirect or theoretical methods are often used to determine the maximum temperature and pressure values.

Some of the important characteristics of an explosive that can be determined by such theoretical computations are:

Oxygen balance
Heat of explosion or reaction
Volume of products of explosion
Potential of the explosive

[edit] Balancing chemical explosion equations

In order to assist in balancing chemical equations, an order of priorities is presented in table 12-1. Explosives containing C, H, O, and N and/or a metal will form the products of reaction in the priority sequence shown. Some observation you might want to make as you balance an equation:

The progression is from top to bottom; you may skip steps that are not applicable, but you never back up.
At each separate step there are never more than two compositions and two products.
At the conclusion of the balancing, elemental nitrogen, oxygen, and hydrogen are always found in diatomic form.

Table 12-1. Order of Priorities
Priority	Composition of explosive	Products of decomposition	Phase of products
1	A metal and chlorine	Metallic chloride	Solid
2	Hydrogen and chlorine	HCl	Gas
3	A metal and oxygen	Metallic oxide	Solid
4	Carbon and oxygen	CO	Gas
5	Hydrogen and oxygen	H₂O	Gas
6	Carbon monoxide and oxygen	CO₂	Gas
7	Nitrogen	N₂	Gas
8	Excess oxygen	O₂	Gas
9	Excess hydrogen	H₂	Gas
10	Excess carbon	C	Solid

Example, TNT:

C₆H₂(NO₂)₃CH₃; → : 7C + 5H + 3N + 6O

Using the order of priorities in table 12-1, priority 4 gives the first reaction products:

7C + 6O → 6CO with one mol of carbon remaining

Next, since all the oxygen has been combined with the carbon to form CO, priority 7 results in:

3N → 1.5N₂

Finally, priority 9 results in: 5H → 2.5H₂

The balanced equation, showing the products of reaction resulting from the detonation of TNT is:

C₆H₂(NO₂)₃CH₃ → 6CO + 2.5H₂ + 1.5N₂ + C

Notice that partial moles are permitted in these calculations. The number of moles of gas formed is 10. The product carbon is a solid.

[edit] Example of thermochemical calculations

The PETN reaction will be examined as an example of thermo-chemical calculations.

PETN: C(CH₂ONO₂)₄

Molecular weight = 316.15 g/mol

Heat of formation = 119.4 kcal/mol

(1) Balance the chemical reaction equation. Using table 12-1, priority 4 gives the first reaction products:

5C + 12O → 5CO + 7O

Next, the hydrogen combines with remaining oxygen:

8H + 7O → 4H₂O + 3O

Then the remaining oxygen will combine with the CO to form CO and CO₂.

5CO + 3O → 2CO + 3CO₂

Finally the remaining nitrogen forms in its natural state (N₂).

4N → 2N₂

The balanced reaction equation is:

C(CH₂ONO₂)₄ → 2CO + 4H₂O + 3CO₂ + 2N₂

(2) Determine the number of molar volumes of gas per mole. Since the molar volume of one gas is equal to the molar volume of any other gas, and since all the products of the PETN reaction are gaseous, the resulting number of molar volumes of gas (N_m) is:

N_m = 2 + 4 + 3 + 2 = 11 V_molar/mol

(3) Determine the potential (capacity for doing work). If the total heat liberated by an explosive under constant volume conditions (Q_m) is converted to the equivalent work units, the result is the potential of that explosive.

The heat liberated at constant volume (Q_mv) is equivalent to the liberated at constant pressure (Q_mp) plus that heat converted to work in expanding the surrounding medium. Hence, Q_mv = Q_mp + work (converted).

a. Q_mp = Q_fi (products) - Q_fk (reactants)

where: Q_f = heat of formation (see table 12-1)

For the PETN reaction:

Q_mp = 2(26.343) + 4(57.81) + 3(94.39) - (119.4) = 447.87 kcal/mol

(If the compound produced a metallic oxide, that heat of formation would be included in Q_mp.)

b. Work = 0.572N_m = 0.572(11) = 6.292 kcal/mol

As previously stated, Q_mv converted to equivalent work units is taken as the potential of the explosive.

c. Potential J = Q_mv (4.185 × 10⁶ kg)(MW) = 454.16 (4.185 × 10⁶) 316.15 = 6.01 × 10⁶ J kg

This product may then be used to find the relative strength (RS) of PETN, which is

d. RS = Pot (PETN) = 6.01 × 10⁶ = 2.21 Pot (TNT) 2.72 × 10⁶

[edit] See also

Explosives used during WW II
Nuclear weapon
Weapon
Explosive velocity
Flame speed
Binary explosive
Explosives safety
Pressure pulse
Orica; largest supplier of commercial explosives
improvised explosive devices

[edit] References

Army Research Office. Elements of Armament Engineering (Part One). Washington, D.C.: U.S. Army Materiel Command, 1964.
Commander, Naval Ordnance Systems Command. Safety and Performance Tests for Qualification of Explosives. NAVORD OD 44811. Washington, D.C.: GPO, 1972.
Commander, Naval Ordnance Systems Command. Weapons Systems Fundamentals. NAVORD OP 3000, vol. 2, 1st rev. Washington, D.C.: GPO, 1971.
Departments of the Army and Air Force. Military Explosives. Washington, D.C.: 1967.
USDOT Hazardous Materials Transportation Placards
Swiss Agency for the Environment, Forests, and Landscap. 'Occurrence and relevance of organic pollutants in compost, digestate and organic residues', Research for Agriculture and Nature. 8 November 2004. p 52, 91, 182.

[edit] External links

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[1] PowerLabs Lead Picrate Synthesis

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