Sulfur mustard

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Sulfur mustard (HD)
Sulfur Mustard

Sulfur Mustard
General
Systematic name Bis (2-chloroethyl) sulfide
Other names Iprit
Kampfstoff "Lost"
Lost
Mustard gas
Senfgas
Yellow Cross Liquid
Yperite
Distilled Mustard
Mustard T- mixture
Molecular formula C4H8Cl2S
Molar mass 159 g/mol
Appearance Colorless if pure.
Normally ranges from
pale yellow to dark brown.
Slight garlic or horseradish type odor[1].

.
CAS numbers [505-60-2]
[39472-40-7]
[68157-62-0]
Properties
Density and phase 1.27 g/ml, liquid
Solubility in water Negligible
Melting point 14.4 °C
Boiling point 217 °C (decomposes)
Vapor pressure 0.11 mmHg @ 25 °C
Hazards
MSDS External MSDS
Main hazards Vesicant
NFPA 704

1
4
1
 
0.003 mg/m3
Flash point 105 °C
Related compounds
Related compounds Nitrogen mustard
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

The sulfur mustards, of which mustard gas is a member, are a class of related cytotoxic, vesicant chemical warfare agents with the ability to form large blisters on exposed skin. In their pure form most sulfur mustards are colorless, odorless, viscous liquids at room temperature. When used as warfare agents they are usually yellow-brown in color and have an odor resembling mustard plants, garlic or horseradish, which is how they got their name. However, these compounds are not related to culinary mustard.

Sulfur mustards are variations of "mustard gas" (bis-(2-chloroethyl) sulfide), which was first synthesised by Frederick Guthrie in 1860, though it is possible that it was developed as early as 1822 by M. Depretz. In 1886 V. Meyer published a paper describing a synthesis which produced good yields. Mustard gas is referred to by numerous other names, including HD, senfgas, sulfur mustard, blister gas, s-lost, lost, Kampfstoff LOST, yellow cross liquid, and yperite. The abbreviation LOST comes from the names Lommel and Steinkopf, who developed a process for mass producing the gas for war use at the German company Bayer AG. This involved reacting thiodiglycol with hydrochloric acid.

Mustard agents, including sulfur mustard, are regulated under the 1993 Chemical Weapons Convention (CWC). Three classes of chemicals are monitored under this Convention, with sulfur and nitrogen mustard grouped in the highest risk class, "schedule 1".

In its history, several varieties and mixtures of sulfur mustard have been employed. Some of those varieties are listed below:

  • H – Also known as HS or Levinstein mustard. Manufactured by reacting dry ethylene with sulfur monochloride under controlled conditions. Undistilled sulfur mustard contains 20–30% impurities, for which reason it does not store as well as HD. Also, as it decomposes, it increases in vapor pressure, making the munition it is contained in likely to split, especially along a seam, thus releasing the agent to the atmosphere[1]
  • HD – Codenamed Pyro by the British, and Distilled Mustard by the US[1]. Distilled sulfur mustard (bis-(2-chloroethyl) sulfide); approximately 96% pure. The term "mustard gas" usually refers to this variety of sulfur mustard.
  • HT – Codenamed Runcol by the British, and Mustard T- mixture by the US[1]

. A mixture of 60% sulfur mustard (HD) and 40% T ([[bis[2-(2-chloroethylthio)ethyl]ether]], a related vesicant with lower freezing point lower volatility and similar vesicant characteristics)

  • HL – A blend of distilled mustard (HD) and lewisite (L)
  • HQ – A blend of distilled mustard (HD) and sesquimustard (Q) (Gates and Moore 1946)

Contents

[edit] Chemistry

Chemically, it is a β-chloro thioether with the formula C4H8Cl2S. Its structure can be described as 1,1-thio-bis-[2-chloroethane], (ClCH2CH2)2S, 2,2′-dichlorodiethyl sulfide or bis-(2-chloroethyl)-sulfide. Mustard gas can be synthesized by reacting sulfur dichloride (SCl2) with two equivalents of ethylene (C2H4).

Although the compound is commonly known as "mustard gas", it is a viscous liquid at normal temperatures. The pure compound has a melting point of 14°C (57°F) and decomposes before boiling at 218°C (423°F).

The compound readily eliminates chloride ion by intramolecular nucleophilic substitution to form a cyclic sulfonium ion. This very reactive intermediate is particularly detrimental to cellular health as it has a strong tendency to bond to the guanine nucleotide in DNA strands. This leads to either immediate cellular death or, as recent research has found, cancer. Mustard gas is not very soluble in water but is very soluble in fat, contributing to its rapid absorption into the skin.

In the wider sense, compounds with the structural element BCH2CH2X, where X is any leaving group and B is a Lewis base are known as mustards. Such compounds can form cyclic onium ions (sulfonium, nitroniums, etc.) that readily react with nucleophiles. Examples are bis-(2-chloroethyl)ether or the (2-haloethyl)amines.

A variant form of mustard gas is Sesquimustard, with the molecular formula C6H12Cl2S2.

Sulfur mustard produces a sulfonium ion, which is attacked by DNA.
Sulfur mustard produces a sulfonium ion, which is attacked by DNA.

[edit] Physiological effects

A soldier with mustard gas burns sustained during World War I.
A soldier with mustard gas burns sustained during World War I.

Mustard gas is a strong vesicant (blister-causing agent). Those exposed usually suffer no immediate symptoms. Within 4 to 24 hours the exposure develops into deep, itching or burning blisters wherever the mustard contacted the skin; the eyes (if exposed) become sore and the eyelids swollen, possibly leading to conjunctivitis and blindness. According to the Medical Management of Chemical Casualties handbook, there have been experimental cases in humans where the patient has suffered miosis, or pinpointing of pupils, as a result of the cholinomimetic activity of mustard. At very high concentrations, if inhaled, it causes bleeding and blistering within the respiratory system, damaging the mucous membrane and causing pulmonary edema. Blister agent exposure over more than 50% body surface area is usually fatal.

Skin damage can be reduced if povidone iodine in a base of glycofurol is rapidly applied, but since mustard initially has no symptoms, the exposure is usually not identified until the blisters rise. The vesicant property can be neutralised by oxidation or chlorination; household bleach (sodium hypochlorite) or decontamination solution "DS2" (2% NaOH, 70% diethylenetriamine, 28% ethylene glycol monomethyl ether) can be used. Mustard gas is also carcinogenic (cancer causing) and mutagenic (causing damage to DNA of exposed cells).

[edit] History

After a failed attempt on the Eastern front, it was first used effectively in World War I by the German army against Canadian soldiers in 1917 and later also against the French – the name Yperite comes from its usage by the German army near the city of Ypres. It took the British over a year to develop their own mustard gas weapon, first using it in September 1918 during the breaking of the Hindenburg Line.

Mustard gas was dispersed as an aerosol in a mixture with other chemicals, giving it a yellow-brown color and a distinctive odor. Mustard has also been dispersed in such munitions as aerial bombs, land mines, mortar rounds, howitzer rounds, and rockets[1]. Mustard gas was lethal in only about 1% of cases. Its effectiveness was as an incapacitating agent: a wounded soldier slows an advancing army much more than a dead one. The countermeasures against the gas were quite ineffective, since a soldier wearing a gas mask was not protected against absorbing it through the skin, although today it would be most ineffective for primary military forces since protective measures have evolved to include chemical protective clothing that covers all of the skin.

Furthermore, mustard gas was a persistent agent which would remain in the environment for days and continue to cause sickness. If mustard gas contaminated a soldier's clothing and equipment, then other soldiers he came into contact with would also be poisoned. Towards the end of the war it was even used in high concentrations as an area-denial weapon, which often forced soldiers to abandon heavily contaminated positions.

Since then, mustard gas has also been reportedly used in several wars, often where the side it is used against cannot retaliate:[2]

Also, in 1943 a U.S. stockpile was bombed in Bari, Italy, accidentally exposing thousands of civilians and 628 Allied troops. It was noted by medical workers that the white cell counts of exposed soldiers were decreased, and mustard gas was investigated as a therapy for Hodgkin's lymphoma, a form of cancer. Study of the use of similar chemicals as agents for the treatment of cancers led to the discovery of mustine, and the birth of anticancer chemotherapy.

During the last months of World War II a very large number of bombs containing Mustard Gas was dropped by the Germans in the Baltic Sea north east of the Danish island Bornholm. From time to time danish fishermen still find bombs containing active Mustard Gas.

The use of poison gas, including mustard gas, during warfare, a practice known as chemical warfare, was prohibited by the Geneva Protocol of 1925 and the subsequent Chemical Weapons Convention of 1993, which also prohibits the development, production and stockpiling of such weapons.

[edit] Disposal of Mustard Gas

Most of the mustard gas found in Germany after World War II was dumped into the Baltic Sea. Between 1966 and 2002, fishermen have found around 700 chemical weapons outside Bornholm, most of which were mustard gas bombs. When mustard gas is exposed to seawater, it forms a tar-like gel and maintains its lethality for at least five years. It is possible to mistake a piece of polymerised mustard gas for ambergris, which can lead to severe health problems. Shells containing mustard gas and other toxic ammunition from World War I (as well as conventional explosives) can still occasionally be found in France and Belgium; they used to be disposed of by explosion at sea, but current environmental regulations prohibit this and so the French government is building an automated factory to dispose of the backlog of shells.

In 1972, The United States Congress banned the practice of disposing chemical weapons into the ocean. However by this point, 64 million pounds of nerve and mustard agents had already been dumped into the ocean waters off of the United States by the U.S. Army. According to a 1998 report created by William Brankowitz, a deputy project manager in the U.S. Army Chemical Materials Agency, the Army created at least 26 chemical weapons dumpsites in the ocean off of at least 11 states on both the west and east coasts. Additionally due to poor records, they currently only know the rough whereabouts of half of them.

A significant portion of the stockpile of mustard agent in the United States was stored at the Edgewood Area of Aberdeen Proving Ground in Maryland. Approximately 1621 tons of mustard agent was stored in one-ton (900 kg) containers on the base under heavy guard. A disposal plant built on site neutralized the last of this stockpile in February, 2005. This stockpile had priority due to the potential for quick reduction of risk to the community. The closest schools were fitted with overpressurization units to protect the students and staff in the event of a catastrophic explosion and fire at the site. These projects, as well as planning, equipment, and training assistance, were provided to the surrounding community as a part of the Chemical Stockpile Emergency Preparedness Program (CSEPP), a joint US Army and Federal Emergency Management Agency program (http://www.fema.gov/government/grant/csepp1.shtm). Unexploded shells containing mustard agent and other chemical agents are still present in several test ranges in proximity to Edgewood area schools, but the smaller amounts (4–14 pounds; 2–6 kg) present considerably less risk. They are being systematically detected and excavated for disposal. There are several other sites in the United States where the remaining US stockpiles of chemical agents are awaiting destruction in compliance with international chemical weapons treaties; the largest mustard agent stockpile, approximately 6196 tons, is stored at the Deseret Chemical Depot in Utah. Destruction of this stockpile began in 2006. US mustard agent and other chemical agent storage is managed by the US Army's Chemical Materials Agency (http://www.cma.army.mil/home.aspx). The Chemical Materials Agency (CMA) manages disposal operations at five of the remaining seven stockpile sites, located in Alabama, Arkansas, Indiana, Utah, and Oregon; disposal projects at the other two sites, located in Kentucky and Colorado, are managed by the Program Manager Assembled Chemical Weapons Alternatives (ACWA) (http://www.pmacwa.army.mil/).

[edit] See also

[edit] External links

[edit] References

  1. ^ a b c d e FM 3-8 Chemical Reference handbook; US Army; 1967
  2. ^ a b c d e f g h i j k Blister Agent: Sulfur Mustard (H, HD, HS), CBWinfo.com
  3. ^ a b c Uses of CW since the First World War, Federation of American Scientists
  4. ^ After the war is over, Economist magazine, 6 March 2003
  5. ^ a b Daniel Feakes (2003). "Global society and biological and chemical weapons", Global Civil Society Yearbook 2003. Oxford University Press, 87-117. 


This article forms part of the series
Chemical warfare
Blood agents: Cyanogen chloride (CK) – Hydrogen cyanide (AC)
Blister agents: Lewisite (L) – Sulfur mustard gas (HD, H, HT, HL, HQ) – Nitrogen mustard gas (HN1, HN2, HN3)
Nerve agents: G-Agents: Tabun (GA) – Sarin (GB) – Soman (GD) – Cyclosarin (GF) – GV | V-Agents: VE – VG – VM – VX | Novichok agents
Pulmonary agents: Chlorine – Chloropicrin (PS) – Phosgene (CG) – Diphosgene (DP)
Incapacitating agents: Agent 15 (BZ) – KOLOKOL-1
Riot control agents: Pepper spray (OC) – CS gas – CN gas (mace) – CR gas
v • d • e
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