Chemistry

ChemistryChemical warfare is the use of natural and man-made toxic
substances to incapacitate or kill an enemy. There are many different types
of agents used in chemical warfare, some of which are mustard gases, nerve
gases, psychotomimetic agents, tear gases, hydrogen cyanide, and arsines.
All of which are very poisonous and lethal when exposed to humans in large
amounts. Until the 20th century such warfare was primarily limited to
starting fires, poisoning wells, distributing smallpox-infected articles,
and using smoke to confuse the enemy. Today however, it is used as lethal
combative.
Mustard agents are usually classified as "blistering agents" owing
to the similarity of the wounds caused by these substances resembling burns
and blisters. However, since mustard agents also cause severe damage to the
eyes, respiratory system and internal organs, they should preferably be
described as "blistering and tissue-injuring agents". Normal mustard agent,
bis-(2-chloroethyl)sulphide, reacts with a large number of biological
molecules. The effect of mustard agent is delayed and the first symptoms do
not occur until between 2-24 hours after exposure.Mustard agent is simple
to manufacture and can therefore be a "first choice" when a country decides
to build up a capacity for chemical warfare.
Mustard agent was produced for the first time in 1822 but its
harmful effects were not discovered until 1860. Mustard agent was first
used as a CW agent during the latter part of the First World War and caused
lung and eye injuries to a very large number of soldiers. Many of them
still suffered pain 30-40 years after they had been exposed, mainly as a
result of injuries to the eyes and chronic respiratory disorders.
In its pure state, mustard agent is colorless and almost odorless.
The name was given to mustard agent as a result of an earlier production
method which yielded an impure mustard-smelling product. Mustard agent is
also claimed to have a characteristic smell similar to rotten onions.
However, the sense of smell is dulled after only a few breaths so that the
smell can no longer be distinguished. In addition, mustard agent can cause
injury to the respiratory system in concentrations which are so low that
the human sense of smell cannot distinguish them.
Symptoms of mustard agent poisoning extend over a wide range. Mild
injuries consist of aching eyes with abundant flow of tears, inflammation
of the skin, irritation of the mucous membrane, hoarseness, coughing and
sneezing. Normally, these injuries do not require medical treatment. Severe
injuries which are incapacitating and require medical care may involve eye
injuries with loss of sight, the formation of blisters on the skin, nausea,
vomiting and diarrhoea together with severe respiration difficulty.
Acute mortality arising from exposure to mustard agent is low. The
dose needed to directly kill a person upon inhalation is, e.g., about 50
times larger than the dose giving acute mortality upon poisoning with the
nerve agent soman. People who die after exposure to mustard agent usually
do so after a few days up to one or more weeks.

Arsines

Among the arsenal of chemical weapons can be found mustard agent
mixed with lewisite which is an aliphatic arsenic compound, 2-
chlorovinyldichloroarsine. Pure lewisite is a colourless liquid. Solubility
in water is approximately the same as for mustard agent but the volatility
is much higher. Hydrolysis in water is faster than for mustard agent.
Injuries caused by lewisite are similar to those caused by mustard agent.
However, the mechanism of action for lewisite is different. From
the diagnostic viewpoint, an important difference is that symptoms in
lewisite poisoning are not delayed and the irritating effect occurs
immediately. Skin damage is treated in the same way as after exposure to
mustard agent. A specific antidote (bal, British Anti Lewisite,
dimercaptopropanol) gives good protection against local injuries to skin
and mucous membrane. bal also has effect against systemic poisoning.
Hydrogen cyanide is usually included among the CW agents causing
general poisoning. There is no confirmed information on this substance
being used in chemical warfare. However, it has been reported

Chemistry 7.7 of 10 on the basis of 2563 Review.