Nitroglycerin | Medical use of Nitroglycerin

Nitroglycerin (NG), (US spelling) also known as nitroglycerine, (UK Spelling), trinitroglycerin, trinitroglycerine and glyceryl trinitrate, is a chemical compound. It is a heavy, colorless, oily, explosive liquid obtained by nitrating glycerol. Since the 1860s, it has been used as an active ingredient in the manufacture of explosives, specifically dynamite, and as such is employed in the construction and demolition industries. Similarly, since the 1880s, it has been used by the military as an active ingredient, and a gellatinizer for nitrocellulose, in some solid propellants, such as Cordite and Ballistite. Nitroglycerin is also used medically as a vasodilator to treat heart conditions, such as angina and chronic heart failure.

Chemical formula
C3H5(NO3)3

Molar mass
227.0872 g/mol

Shock sensitivity
Very High

Friction sensitivity
Very high

Density
1.6 g/cm³ at 15 °C

Explosive velocity
7700 m/s

RE factor
1.50

Melting point
13.2 °C (55.76 °F)

Autoignition temperature
Decomposes at 50 to 60 °C (122 to 140 °F)

Appearance
Clear yellow/colorless oily liquid

History

Nitroglycerin was discovered by chemist Ascanio Sobrero in 1846, working under TJ Pelouze at the University of Turin. The best manufacturing process was developed by Alfred Nobel in the 1860s. His company exported a liquid combination of nitroglycerin and gunpowder as 'Swedish Blasting Oil', but it was extremely dangerous as a result of its extreme instability, as shown in numerous "appalling catastrophes," such as the explosion that destroyed a Wells Fargo office in San Francisco in 1866.

Liquid nitroglycerin was widely banned, and this led to the development of dynamite (and similar mixtures, such as blasting gelatine, dualine and lithofracteur), made by mixing the nitroglycerin with inert absorbents; for example, Nobel used kieselguhr. Other nitrated materials, such nitrocellulose gel, were also used.

Instability and desensitization

In its pure form, it is a contact explosive (physical shock can cause it to explode) and degrades over time to even more unstable forms. This makes it highly dangerous to transport or use. In this undiluted form, it is one of the most powerful high explosives, comparable to the newer military explosives RDX and PETN (which are not used in munitions at full concentration because of their sensitivity); as well as the plastic explosive C-4—which contains over 90% RDX, as its active ingredient.

Early in the history of this explosive it was discovered that liquid nitroglycerin can be "desensitized" by cooling to 5 to 10 °C (40 to 50 °F), at which temperature it freezes, contracting upon solidification. However, later thawing can be extremely sensitizing, especially if impurities are present or if warming is too rapid. It is possible to chemically "desensitize" nitroglycerin to a point where it can be considered approximately as "safe" as modern high explosive formulations, by the addition of approximately 10-30% ethanol, acetone, or dinitrotoluene (percentage varies with the desensitizing agent used).

Desensitization requires extra effort to reconstitute the "pure" product. Failing this, it must be assumed that desensitized nitroglycerin is substantially more difficult to detonate, possibly rendering it useless as an explosive for practical application.

A serious problem in the use of nitroglycerin results from its high freezing point 13 °C (55 °F). Solid nitroglycerin is much less sensitive to shock than the liquid, a feature common in explosives; in the past it was often shipped in the frozen state, but this resulted in a high number of accidents during the thawing process by the end user just prior to use. This disadvantage is overcome by using mixtures of nitroglycerin with other polynitrates; for example, a mixture of nitroglycerin and ethylene glycol dinitrate freezes at -29 °C (-20 °F).[1]

Detonation

Nitroglycerin and any or all of the dilutents used can certainly deflagrate or burn. However, the explosive power of nitroglycerin is derived from detonation: energy from the initial decomposition causes a pressure gradient that detonates the surrounding fuel. This can generate a self-sustained shock-wave that propagates through the fuel-rich medium at or above the speed of sound as a cascade of near-instantaneous pressure-induced decomposition of the fuel into gas. This is quite unlike deflagration, which depends solely upon available fuel, regardless of pressure or shock.

Manufacturing of Nitroglycerin

The industrial manufacturing process often uses a nearly 50:50 mixture of sulfuric acid and nitric acid. This can be produced by mixing white fuming nitric acid (quite costly pure nitric acid in which oxides of nitrogen have been removed, as opposed to red fuming nitric acid) and concentrated sulfuric acid. More often, this mixture is attained by the cheaper method of mixing fuming sulfuric acid (sulfuric acid containing excess sulfur trioxide) and azeotropic nitric acid (consisting of around 70% nitric acid, the rest being water).

The sulfuric acid produces protonated nitric acid species, which are attacked by glycerin's nucleophilic oxygen atoms. The nitro group is thus added as an ester C-O-NO2 and water is produced. This is different from an aromatic nitration reaction in which nitronium ions are the active species in an electrophilic attack of the molecules ring system.

The addition of glycerin results in an exothermic reaction (i.e., heat is produced), as usual for mixed acid nitrations. However, if the mixture becomes too hot, it results in runaway, a state of accelerated nitration accompanied by the destructive oxidizing of organic materials of nitric acid and the release of very poisonous brown nitrogen dioxide gas at high risk of an explosion. Thus, the glycerin mixture is added slowly to the reaction vessel containing the mixed acid (not acid to glycerin). The nitrator is cooled with cold water or some other coolant mixture and maintained throughout the glycerin addition at about 22 °C, much below which the esterification occurs too slowly to be useful. The nitrator vessel, often constructed of iron or lead and generally stirred with compressed air, has an emergency trap door at its base, which hangs over a large pool of very cold water and into which the whole reaction mixture (called the charge) can be dumped to prevent an explosion, a process referred to as drowning. If the temperature of the charge exceeds about 10 °C (actual value varying by country) or brown fumes are seen in the nitrators vent, then it is immediately drowned.

Because of the great dangers associated with its production, most nitroglycerin production facilities are in offshore rigs or very remote locations.

Use as an explosive and a propellant

The main use of Nitroglycerin, by tonnage, is in explosives such as dynamite and in propellants.

Alfred Nobel developed the use of nitroglycerin as a blasting explosive by mixing the nitroglycerine with inert absorbents particularly kieselguhr. He named this explosive Dynamite and patented it in 1867. It was supplied ready for use in the form of sticks, individually wrapped in grease proof paper. Dynamite and similar explosives were widely adopted for civil engineering tasks, such as building railway tunnels and cuttings; and for quarrying.
Nitroglycerin was also adapted as a military propellant, for use in guns and rifles. Poudre B, invented in France in 1886, was one of the first military propellants to replace gunpowder; but it was based on nitrocellulose, not nitroglycerin. It was later found to be unstable.

Alfred Nobel then developed Ballistite, by combining nitroglycerin and guncotton. He patented it in 1887. Ballistite was adopted by a number of European governments, as a military propellant. Italy was the first to adopt it. However, it was not adopted by the British Government. They, together with the British Commonwealth countries, adopted Cordite, which had been developed by Sir Frederick Abel and Sir James Dewar, in 1889. The original

Cordite Mk I consisting of 58% nitroglycerine, 37% guncotton and 5%

Petroleum jelly. Ballistite and Cordite were both manufactured in the forms of cords.

Smokeless powders were originally developed using nitrocellulose as the sole explosive ingredient; and were therefore known as single base propellants. A range of smokeless powders that contain both nitrocellulose and nitroglycerin, known as double base propellants, were also developed. Smokeless powders were originally supplied only for military use; however they were also soon developed for civilian use and were quickly adopted for sport. Some are known as sporting powders.

War time production rates

Large quantities of nitroglycerin were manufactured in both World Wars for use in military propellants.

World War I

In World War I HM Factory, Gretna, the largest propellant factory in the United Kingdom was producing 800 tons (812 tonne) of Cordite RDB per week. This required 336 tons of nitroglycerin per week (assuming no losses in production). The Royal Navy had its own factory at Royal Navy Cordite Factory, Holton Heath.

A large cordite factory was also built in Canada in World War I. The Canadian Explosives Limited Cordite factory at Nobel, Ontario was designed to produce 1,500,000 lb (681 tonne) of Cordite per month. It required 286 tonnes of nitroglycerin per month.

Medical use of Nitroglycerin

Nitroglycerin in medicine, where it is generally called glyceryl trinitrate, is used as a heart medication (under the trade names Nitrospan®, Nitrostat®, and Tridil®, amongst others). It is used as a medicine for angina pectoris (ischaemic heart disease) in tablets, ointment, solution for intravenous use, transdermal patches (Transderm Nitro®, Nitro-Dur®), or sprays administered sublingually (Nitrolingual Pump Spray®, Natispray®).

The principal action of nitroglycerin is vasodilation—widening of the blood vessels. Nitroglycerin will dilate veins more than arteries, decreasing cardiac preload and leading to the following therapeutic effects during episodes of angina pectoris:
subsiding of chest pain
decrease of blood pressure
increase of heart rate.
orthostatic hypotension

These effects arise because nitroglycerin is converted to nitric oxide in the body (by a mechanism that is not completely understood), and nitric oxide is a natural vasodilator. Recently, it has also become popular in an off-label use at reduced (0.2%) concentration in ointment form as an effective treatment for anal fissure.

Industrial exposure

Infrequent exposure to high doses of nitroglycerin can cause severe headaches known as "NG head". These headaches can be severe enough to incapacitate some people; however, humans develop a tolerance and dependence to nitroglycerin after long-term exposure. Withdrawal can (rarely) be fatal; withdrawal symptoms include headaches and heart problems; with re-exposure to nitroglycerin, these symptoms may disappear.

For workers in nitroglycerin manufacturing facilities, this can result in a "Monday morning headache" phenomenon for those who experience regular nitroglycerin exposure in the workplace; over the weekend they develop symptoms of withdrawal, which are then countered by re-exposure on the next work day.

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Ballistite | Smokeless Powder | Vielle's powder | Nitrocellulose deteriorate

Smokeless powder is the general name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older (Gunpowder) black powder which they replaced.

Types of smokeless powder include Cordite, Ballistite and, historically, Poudre B. They are classified as single-base, double-base or triple-base powders.

Smokeless powder consists of nitrocellulose (single-base powders), frequently combined with up to 50 percent nitroglycerin (double-base powders), and sometimes nitroglycerin and nitroguanidine (triple-base), corned into small spherical balls or extruded into cylinders or flakes using solvents such as ether. Other minor ingredients, such as stabilizers and ballistic modifiers, are also added. Double-base propellants are common in handgun and rifle ammunition. Triple-base propellants are more common in artillery guns.

The reason that they are smokeless is that the combustion products are mainly gaseous, compared to around 55% solid products for black powder (potassium carbonate, potassium sulfate etc).

Smokeless powder burns only on the surfaces of the granules, flakes or cylinders - described as granules for short. Larger granules burn more slowly, and the burn rate is further controlled by flame-deterrent coatings which retard burning slightly. The intent is to regulate the burn rate so that a more or less constant pressure is exerted on the propelled projectile as long as it is in the barrel so as to obtain the highest velocity. Cannon powder has the largest granules, up to thumb-sized cylinders with seven perforations (one central and the other six in a circle halfway to the outside of the cylinder's end faces). The perforations stabilize the burn rate because as the outside burns inward (thus shrinking the burning surface area) the inside is burning outward (thus increasing the burning surface area, but faster, so as to fill up the increasing volume of barrel presented by the departing projectile). Fast-burning pistol powders are made by extruding shapes with more area such as flakes or by flattening the spherical granules. Drying is usually performed under a vacuum.

The solvents are condensed and recycled. The granules are also coated with graphite to prevent static electricity sparks from causing undesired ignitions.



History

Military commanders had been complaining since the Napoleonic Wars about the problems of giving orders on a battlefield that was covered in thick smoke from the gunpowder used by the guns. A major step forward was introduced when guncotton, a nitrocellulose-based material, was first introduced by Christian Friedrich Schönbein in 1846. He also promoted its use as a blasting explosive.


Guncotton was more powerful than gunpowder, but at the same time was somewhat more unstable. This made it unsuitable as a propellant for small firearms: not only was it dangerous under field conditions, but guns that could fire thousands of rounds using gunpowder would be "used up" after only a few hundred with the more powerful guncotton. It did find wide use with artillery. However, within a short time there were a number of massive explosions and fatalities in guncotton factories due to lack of appreciation of its sensitivity and the means of stabilization. Guncotton then went out of use for some twenty years or more until it could be tamed; it was not until the 1880s that it became a viable propellant.

In 1884 Paul Vieille invented a smokeless gunpowder called Poudre B, made from gelatinized guncotton mixed with ether and alcohol. It was passed through rollers to form thin sheets, which were cut into flakes of the desired size. The resulting propellant, today known as pyrocellulose, contains somewhat less nitrogen than guncotton and is less volatile. A particularly good feature of the propellant is that it will not burn unless it is compressed, making it very safe to handle under normal conditions.

Vieille's powder revolutionized the effectiveness of small guns, for several reasons. First, it gave off almost no smoke. After a few shots, a soldier with black powder ammunition would have his view obscured by a huge pall of smoke unless there was a strong wind. Conversely, a sniper or other hidden shooter would not be given away by a cloud of smoke over the firing position. Further, it was three times more powerful than black powder, which gave more power from less powder. The higher muzzle velocity meant a flatter trajectory and therefore more accurate long range fire, out to perhaps 1000 metres in the first smokeless powder rifles. Since less powder was needed to propel a bullet, the cartridge could be made smaller and lighter. This allowed troops to carry more ammunition for the same weight. Also, it would burn even when wet. Black powder ammunition had to be kept dry and was almost always stored and transported in watertight cartridges.

Vielle's powder was used in the Lebel rifle that was immediately introduced by the French Army to exploit its huge benefits over black powder. Other European countries swiftly followed and started using their own versions of Poudre B, the first being Germany and Austria which introduced new weapons in 1888.

Meanwhile, in Great Britain, in 1887, Alfred Nobel developed a smokeless gunpowder called Ballistite. A modified form of this was devised by Sir Frederick Abel and James Dewar which eventually became known as Cordite, leading to a lengthy court battle between Nobel and the other two inventors over alleged British patent infringement. In the USA, in 1890, a patent for smokeless powder was obtained by Hudson Maxim.

These newer propellants were more stable and thus safer to handle than Poudre B, and also more powerful. Today, propellants based on nitrocellulose alone are known as single-base, whereas cordite-like mixtures are known as double-base. A triple-base flashless cordite was also developed, primarily for large naval guns, but also used in battle tank ammunition.

Smokeless powder allowed the development of modern semi- and fully automatic firearms. Burnt blackpowder leaves a thick, heavy fouling which is both hygroscopic and corrosive. Smokeless powder fouling exhibits none of these properties. This makes an autoloading firearm with many moving parts feasible (which would jam or seize under heavy blackpowder fouling).

Single and double-base smokeless powders now make up the vast majority of propellants used in firearms. They are so common that most modern references to "gunpowder" refer to a smokeless powder, particularly when referring to small arms ammunition.


Instability and stabilization

Nitrocellulose deteriorates with time, yielding acidic byproducts. Those byproducts catalyze the further deterioration, increasing its rate. The released heat, in case of bulk storage of the powder, or too large blocks of solid propellant, can cause self-ignition of the material. Single-base nitrocellulose propellants are most susceptible to degradation; double-base and triple-base propellants tend to deteriorate more slowly. To neutralize the decomposition products, which could otherwise cause corrosion of metals of the cartridges and gun barrels, calcium carbonate is added to some formulations.
To prevent buildup of the deterioration products, stabilizers are added. 2-Nitrodiphenylamine is one of the most common stabilizers used. Others are 4-nitrodiphenylamine, N-nitrosodiphenylamine, N-methyl-p-nitroaniline, and diphenylamine. The stabilizers are added in the amount of 0.5-2% of the total amount of the formulation; higher amounts tend to degrade its ballistic properties. The amount of the stabilizer is depleted with time. Propellants in storage should be periodically tested on the remaining amount of stabilizer, as its depletion may lead to autoignition of the propellant.

Smokeless propellant components

The propellant formulations may contain various energetic and auxiliary components:

Propellants:
Nitrocellulose, an energetic component of most smokeless propellants
Nitroglycerin, an energetic component of double-base and triple-base formulations
Nitroguanidine, a component of triple-base formulations
Plasticizers, to make the grains less brittle
Dibutyl phthalate
Polyester adipate
Dinitrotoluene (toxic, carcinogen, obsoleted)
Binders, to hold the grain shape
Rosin
Ethyl acetate
Stabilizers, to prevent or slow down self-decomposition
Diphenylamine
2-Nitrodiphenylamine
4-nitrodiphenylamine
N-nitrosodiphenylamine
N-methyl-p-nitroaniline
Decoppering additives, to hinder the buildup of copper residues from the gun barrel rifling
Tin metal and compounds, e.g. tin dioxide
Bismuth metal and compounds, e.g. bismuth trioxide, bismuth subcarbonate, bismuth nitrate, bismuth antimonide; the bismuth compounds are favored as copper dissolves in molten bismuth, forming brittle and easily removable alloy
Lead foil and lead compounds, phased out due to toxicity
Flash reducers, to reduce the brightness of the muzzle flash
Potassium nitrate
Potassium sulfate (both have a disadvantage - production of smoke)
Wear reduction additives, to lower the wear of the gun barrel liners USA 16"/50 (40.6 cm) Mark 7
Wax
Talc
Titanium dioxide
Polyurethane jackets over the powder bags, in large guns

Other additives
Graphite, a lubricant to cover the grains and prevent them from sticking together, and to dissipate static electricity

Calcium carbonate, to neutralize acidic decomposition products
The properties of the propellant are greatly influenced by the size and shape of its grains. The surface of the grains influences the speed of burning, and the shape influences the surface and its change during burning. By selection of the grain shape it is possible to influence the pressure vs time curve as the propellant burns.

Faster-burning propellants generate higher temperatures and higher pressures, however they also increase the wear of the gun barrels.
A Primex powder contains 0-40% nitroglycerin, 0-10% dibutyl phthalate, 0-10% polyester adipate, 0-5% rosin, 0-5% ethyl acetate, 0.3-1.5% diphenylamine, 0-1.5% N-nitrosodiphenylamine, 0-1.5% 2-nitrodiphenylamine, 0-1.5% potassium nitrate, 0-1.5% potassium sulfate, 0-1.5% tin dioxide, 0.02-1% graphite, 0-1% calcium carbonate, and nitrocellulose as the remainder to 100%

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Nitrocellulose lacquer | Nitrocellulose uses

Nitrocellulose (also: cellulose nitrate, flash paper) is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton.

Uses of Nitrocellulose

Nitrocellulose is a major component of smokeless gunpowder (also see the section on guncotton below).
Early photographic film, especially black-and-white film prior to 1948.
Nitrocellulose membrane or nitrocellulose paper is a sticky membrane used for Western blots and immobilizing DNA.
It is also used for immobilization of proteins, due to its non-specific affinity for amino acids. Nitrocellulose is widely used as support in diagnostic tests where antigen-antibody binding occur, e.g. pregnancy tests, U-Albumin tests and CRP.
When dissolved in ether or other organic solvents, the solution is called collodion, which has been used as a wound dressing and carrier of topical medications since the U.S. Civil War. To this day it is used in Compound W Wart Remover as a carrier of salicylic acid, the active ingredient.
Collodion was also used as the carrier for silver salts in some very early photographic emulsions, particularly spread in thin layers on glass plates.

Magician's "flash paper", sheets of paper or cloth made from nitrocellulose, which burn almost instantly, with a bright flash, and leave no ash.
Nail polish
Hair coloring
Radon tests for alpha track etches
Nitrocellulose lacquer was used as a finish on guitars for most of the 20th century and is still used on some current applications. Manufactured by (among others) Dupont, the paint was also used on automobiles sharing the same color codes as many guitars, primarily Fender brands of guitars.

Nitrocellulose lacquer is also used as an aircraft dope, painted onto fabric-covered aircraft to tauten and provide protection to the material.
As a transportation medium for one-time pads, thus making the disposal of the pad complete, secure, and efficient.

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