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Essay/Term paper: Chloroflourocarbons

Essay, term paper, research paper:  Science Research Papers

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Chloroflourocarbons


Chloroflourocarbons were discovered in the 1920's by Thomas Midgley, an
organic chemist at General Motors Corporation. He was looking for inert, non-
toxic, non-flammable compounds with low boiling points that could be used as
refrigerants. He found what he was looking for in the form of two compounds:
dichlorodifluoromethane (CFC-12) and trichloromonoflouromethane (CFC-11). In
both compounds, different amounts of chlorine and fluorine are combined with
methane, which is a combination of carbon and hydrogen. These two CFCs were
eventually manufactured by E.I. du Pont de Nemours and company, and, under the
trade name "freon," constituted 15% of the market for refrigerator gases.
CFCs were the perfect answer for cooling refrigerators and air
conditioners. They were easily turned into liquid at room temperature with
application of just a small amount of pressure, and they could easily then be
turned back into gas. CFCs were completely inert and not poisonous to humans.
They became ideal solvents for industrial solutions and hospital sterilants.
Another use found for them was to blow liquid plastic into various kinds of
foams.
In the 1930's, household insecticides were bulky and hard to use, so CFCs
were created because they could be kept in liquid form and in an only slightly
pressurized can. Thus, in 1947, the spray can was born, selling millions of
cans each year. Insecticides were only the first application for CFC spray cans.
They soon employed a number of products from deodorant to hair spray. In 1954,
188 million cans were sold in the U.S. alone, and four years later, the number
jumped to 500 million. CFC filled cans were so popular that, by 1968, 2.3
billion spray cans were sold in America.
The hopes of a seemingly perfect refrigerant were diminished in the late
1960's when scientists studied the decomposition of CFCs in the atmosphere.
What they found was startling. Chlorine atoms are released as the CFCs
decompose, thus destroying the Ozone (O3) atoms in the high stratosphere. It
became clear that human usage of CF2Cl2 and CFCl3, and similar chemicals were
causing a negative impact on the chemistry of the high altitude air.
When CFCs and other ozone-degrading chemicals are emitted, they mix with
the atmosphere and eventually rise to the stratosphere. CFCs themselves do not
actually effect the ozone, but their decay products do. After they photolyzed,
the chlorine eventually ends up as "reservoir species" - they do not themselves
react with ozone- such as Hydrogen Chloride, HCL, or Chlorine Nitrate, ClONO2.
These than further decompose into ozone hurting substances. The simplest is as
follows: (How do CFCs Destroy the Ozone) Cl + O3 -----> ClO + O2 ClO + O
------> Cl + O2 O3 + O -------> 2 O2
The depletion of the ozone layer leads to higher levels of ultraviolet
radiation reaching Earth's surface. Therefore, this can lead to a greater
number of cases of skin cancer, cataracts, and impaired immune systems, and is
expected to reduce crop yields, diminish the productivity of the oceans, and
possibly contribute to the decline of amphibious populations that is occurring
in the world. Besides CFCs, carbon tetrachloride methyl bromide, methyl
chloroform, and halons also destroy the ozone.
In 1985, the degradation of the ozone layer was confirmed when a large hole
in the layer over Antarctica was reported. The hole's existence is due to
industrial chemicals which were manufactured there. During September/October of
1985, up to 60 percent of the ozone had been destroyed. Since then, smaller yet
significant stratospheric decreases have been seen over more populated regions
of the Earth.
Worldwide monitoring has shown that stratospheric ozone has been
decreasing for more than 20 years. The average loss across the globe totaled
about five percent since the mid-1960's with cumulative losses of about ten
percent in the winter and spring. A five percent loss occurs in the summer and
autumn over North America, Europe, and Australia.
The world has been forced to address this issue. Thus, the major powers
of the world created a global treaty, the Vienna Convention for the Protection
of the Ozone Layer. The agreement was put into affect in 1988 and the
subsequent Montreal Protocol on Substances that Deplete the Ozone layer went
into effect in 1989. To date, 140 countries are acknowledging the Montreal
Treaty. The countries decided on a timetable for countries to reduce and to end
their production and consumption of eight major halocarbons. The timetable was
accelerated in 1990 and 1992. Various amendments were adopted in response to
scientific evidence that stratospheric ozone is depleting at a much faster rate
than was predicted.
On the home front, the U.S. Environmental Protection Agency (EPA), under
authority of the U.S. Clean Air Act, have issued regulations for the phase out
of production and importation of ozone depleting chemicals. The EPA established
various policies such as refrigerant recycling in both cars and stationary units,
a ban on nonessential products, labeling requirements, and a requirement to
revise federal procurement specifications.
One of the largest single uses of CFCs is as a refrigerant (CFC-12) used
in automobile air conditioners. Since a big source of this CFC-12 is leaking
automobile air conditioners, many new environmental rules have an impact on the
auto service and repair industry. (1) Anyone repairing or servicing motor
vehicle air conditioners must recover and/or recycle CFCs on-site or recover
CFCs and send them off-site for recycling. (2) Everyone dealing with A/C must
be certified to use CFC recovery and recycling equipment. The shop must own EPA-
approved recovery and recycling equipment. (3) Retailers can only sell cans of
automotive refrigerant (less than 20 pounds) to certified technicians. This
discourages do-it-yourselfers from topping off their own A/C.
The fines for violating any of these rules can run as much as $25,000
per violation.
If someone wants to keep working on A/C, they will have to make an
investment in equipment. Is it worth it? Recovery-only units cost about $500 and
recovery/recycling units run from $1,800 to $5,000. People working on air
conditioning units must pass an EPA-approved CFC recycling course. CFC-12 used
in motor vehicles was phased out of production at the end of 1995. No more will
be made.
CFCs, when first developed, were thought to be a miracle compound. They
made excellent refrigerants, pesticides, deodorants, packaging foam, and had
many other uses. Unfortunately, a hole in the stratosphere was found over
Antarctica in 1985, and CFCs were to blame. Since 1989, numerous laws and
restrictions have been made to stop production of CFCs and allow the ozone in
the stratosphere to replenish itself. Fortunately, the laws and restrictions
have been effective and the ozone layer is slowly but surely filling in. The
future of the ozone layer looks good indeed.

Bibliography

Atmospheric Civic Homepage [on-line] http://www.epa.gov/Ozone/defns.html#cfc

Dolan, Edward. Our Poisoned Sky. Cobblehill books, New York: 1991

EPA's Stratospheric Ozone Protection Program World Wide Web Site [on-line]
http://www.epa.gov/docs/ozone/index.html, March 8, 1997.

Gay, Kathylyn. Ozone. Impact, New York: 1989.

Hoff, Mary and Mary Rodgers. Our endangered Planet Atmosphere. Lener Publication
Company, Minneapolis: 1995.

Preston, James. Air Conditioning and Refrigeration Technician's EPA
Certification Guide, Quality Books, New York: 1994.

Roan, Sharon. Ozone Crisis. Wiley science editions, New York: 1989.

 

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