The Element: Chlorine
General Information
We researched the chemical element known as chlorine. Chlorine has
an atomic number of 17 and an atomic weight of 35.453. It has a
valence number of 3. The element has 3 energy levels. Chlorine exists
as a greenish-yellow gas at normal temperatures and pressures. Chlorine
is second in reactivity only to fluorine among the halogen elements.

Chlorine is a nonmetal. It is estimated that 0.045% of the earths
crust and 1.9% of sea water are chlorine. Chlorine combines with
metals and nonmetals and organic materials to form hundreds of
chlorine compounds. Chlorine is about 2.5 times as dense as air and
moderately soluble in water, forming a pale yellowish green solution.

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Chlorine is so reactive that it never occurs free in nature.

Chemical Properties
Chlorine is in the halogen family, and like all the other
halogen elements chlorine has a strong tendency to gain one electron
and become a chloride ion. Chlorine readily reacts with metals to form
chlorides, most of which are soluble in water. Chlorine also reacts
directly with many nonmetals such as sulfur, phosphorus, and other
halogens. Chlorine can support combustion; if a candle were to be thrown
into a vessel of chlorine, it would continue to burn, releasing dense,
black clouds of smoke, The chlorine combines with hydrogen of the
paraffin, forming hydrogen chloride, and uncombined carbon is left in
the form of soot. Soot is black residue from fuel. Chlorine replaces
iodine and bromine from their salts. Dry chlorine is somewhat inert or
not able to move, but moist chlorine unites directly with most of the

Chlorine was discovered in 1774 by Karl Scheele. Humphry Davy
proved that chlorine was an element. Extensive production began 100
years later. During the 20th Century. The amount of Chlorine used was
considered a measure of industrial growth. In, 1975 chlorine
productions ranked seventh on the list of largest-volume chemicals
produced in the United States. The importance of chlorine has changed
as new uses have been added. In 1925 paper and pulp used over one-
half . The chlorine made and chemical products only 10%. By the 1960s
paper and pulp use accounted for only 15-17% and the chemical uses
increased to 75-80%. Peoples uses have contributed to the growth of
large cities, and new textiles, plastics, paints, and miscellaneous uses
have raised mans standard of living. Many large companies are based
primarily on the manufacture of chlorine and its compounds. In 1978
17% of the United States production went into the production of vinyl
chloride monomer. Other chlorinated organics consumed 48% of United
States Production.

Toxicity and Precautions
Chlorine was used in World War I as a poison gas. In fact
most poisonous gases have chlorine in them. Chlorine is very corrosive
to moist tissue and has a very irritating effect on the lungs and
mucous membranes of the nose and throat. Inhalation of chlorine gas
can cause edema of the lungs and respiratory stoppage. When hydrogen
and chlorine gases are mixed together, the mixture is stable if kept
in a cool, dark place. If heated or exposed to sunlight, the mixture
explodes. Chlorine is easily liquefied and usually transported in its
liquid state in pressurized drums. Great care must be taken, however,
to prevent the containers from bursting and liberating large amounts
of the gas. In the United States most European countries, large
quantities of chlorine may only be transported by train. The present
trend is to limit the transport of chlorine as much as possible by
producing and using the element in the same location.

Chlorine has many great uses. Chlorine is an excellent
oxidizing agent. At first. The use of Chlorine was used as a
bleaching agent in the paper, pulp, and textile industries and as a
germicide for drinking water preparation swimming pool purification, and
hospital sanitation has made community living possible.

Chlorine is used in bleaching as said before. The bleaching
action of chlorine in aqueous solution is due to the formation of
hypochlorous acid, a powerful oxidizing agent. If a colored, oxidizable
material is present, hypochlorous acid releases its oxygen to oxidize
the material to a colorless compound. Liquid bleach is usually an
aqueous solution of sodium hypochlorite, and dry powder bleaches
contain chloride of lime. Since chlorine destroys silk and wool,
commercial hypochlorite bleaches should never be used on these fibers.

Chlorine is also used as a disinfectant. The oxidizing ability
of chloride of lime enables it to destroy bacteria; therefore large
amounts are used to treat municipal water systems. This chemical is
also used in swimming pools and for treating sewage.

Chlorine is used as rock salt. Sodium chloride, NaCl, is used
directly as mined (rock salt), or as found on the surface, or as
brine also known as salt water. It can be dissolved, purified, and
reprecipated or given in return for use in foods or when chemical
purity is required. Its main uses are in the production of soda ash
and chlorine products. The form uses it as refrigeration, dust, and
ice control, food processing, and food preservation. Calcium chloride,
CaCl2, is usually obtained from salt water or as a by product of
chemical processing. Its main uses are road treatment, coal treatment,
and concrete conditioning.

In addition to these products, for which chlorine is needed,
various other chlorine compounds play an important part in chemistry
and the chemical industry. The chlorides of most metals are easily
soluble in water, which widens their applicability. Some other
important compounds are the chlorates, the perchlorates, and the
hypochlorites. Hydrochloric acid is one of the most frequently used

The most important method for preparation of chlorine is the
electrolysis of a solution of common salt, sodium chloride. The
chlorine gas is liberated at the positive anode or positively charged
electrode, which is made of graphite since a metal anode would react
with chlorine. At the iron cathode or negatively charged electrode,
sodium ions are reduced to sodium metal, which reacts immediately with
water to form sodium hydroxide.

Another method of preparing chlorine is by the electrolysis of
molten salt. This process is used specifically to produce sodium, and
the chlorine is a commercial by product. When large quantities of
waste hydrochloric and are available. Chlorine may be recovered by
oxidation of the acid. This method has the advantage of converting
great quantities of waste acid to useful substances.

No matter what process is used to prepare chlorine, the gas
must be well dried. Dry chlorine is much less corrosive than moist
chlorine gas. In the laboratory chlorine may be prepared by heating
manganese oxide with hydrochloric acid.

In conclusion chlorine is a very wonderful element. Chlorine has
hundreds of compounds. If we did not have these compounds we would
not have clean water, we would have an insect problem, we could not
make many important compounds that are used in medicine, and some of
the battles in World War I might have been lost if it were not for
chlorine. Our world would not be the same if not for chlorine.