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tetrachloroethylene

 
Dictionary: tet·ra·chlo·ro·eth·yl·ene   (tĕt'rə-klôr'ō-ĕth'ə-lēn', -klōr'-) pronunciation also tet·ra·chlor·eth·yl·ene
 
(-klôr-ĕth'-, -klōr-)
n.

Perchloroethylene.


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Encyclopedia of Public Health: Tetrachloroethylene
 

Tetrachloroethylene is a dry-cleaning agent and industrial degreaser that often goes under the name perchloroethylene (PERC). The National Institute of Occupational Safety and Health estimates that 650,000 U.S. workers are exposed to PERC annually. PERC enters the environment through evaporation or through transport into groundwater and drinking water supplies. Through widespread use it has become a frequent drinking water contaminant, and it is present in approximately half of the nation's Superfund sites.

PERC has a low odor threshold and its smell is that associated with a dry-cleaning establishment. High levels of PERC released in workplace accidents can produce loss of consciousness and death. There is some evidence that longer-term exposures to lower levels at the workplace can lead to kidney and liver damage, cancer, neurological impairment, including changes in memory and learning, and to problems with visual perception. Reproductive and developmental effects have been suggested.

Whether any of these effects occur at the much lower levels present in the general environment is controversial. There is increased pressure to regulate PERC because of particular concern for children living in apartment buildings above dry-cleaning establishments, and because as a chlorinated compound it can be a precursor of dioxins.

(SEE ALSO: Dioxins; Toxicology)

Bibliography

New York State Department of Health (1997). Tetrachloroethylene (PERC) in Indoor and Outdoor Air: Fact Sheet. Albany, NY: Author.

U.S. Health Department of Health and Human Services (1997). Toxicological Profile for Tetrachloroethylene. Washington, DC: Public Health Service, Agency for Toxic Substances and Disease Registry.

— BERNARD D. GOLDSTEIN



 
Veterinary Dictionary: tetrachloroethylene
Top

A clear, colorless liquid used extensively at one time as an anthelmintic but now superseded in all species by safer and more effective drugs. Overdosing causes incoordination immediately, hepatic insufficiency later.

 
WordNet: tetrachloroethylene
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Note: click on a word meaning below to see its connections and related words.

The noun has one meaning:

Meaning #1: anthelmintic agent used against hookworm and other nematodes
  Synonyms: tetrachlorethylene, ethylene tetrachloride, carbon dichloride


 
Wikipedia: Tetrachloroethylene
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Tetrachloroethylene
Tetrachloroethylene
Tetrachloroethylene
IUPAC name
Other names perchloroethene
perchloroethylene
perc, PCE
Identifiers
CAS number [127-18-4]
EC number 204-825-9
RTECS number KX3850000
SMILES
Properties
Molecular formula C2Cl4
Molar mass 165.8 g/mol
Appearance Clear, colorless liquid
Density 1.622 g/cm3, liquid
Melting point

−19 °C (254 K)

Boiling point

121.1 °C (394 K)

Solubility in water 0.015 g/100 ml (20 °C)
Viscosity 0.89 cP at 25 °C
Hazards
MSDS External MSDS
R-phrases 40-51/53
S-phrases 23-36/37-61
Flash point Not flammable
Related compounds
Related Related Haloforms tetrabromoethylene
tetraiodoethylene
Related compounds trichloroethylene
dichloroethene
tetrachloroethane
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox references

Tetrachloroethylene, also known under its systematic name tetrachloroethene and as perchloroethylene, perchloroethene, perc, and PCE, is a chlorocarbon with the formula Cl2C=CCl2. It is a colourless liquid widely used for dry cleaning of fabrics, hence it is sometimes called "dry-cleaning fluid." It has a sweet odor detectable by most people at a concentration of 1 part per million (1 ppm). Worldwide production was about 1 megaton in 1985.[1]

Contents

Production

Michael Faraday first synthesized tetrachloroethene in 1821 by thermal decomposition of hexachloroethane into tetrachloroethene and chlorine.

C2Cl6 → C2Cl4 + Cl2

Most tetrachloroethene is produced by high temperature chlorinolysis of light hydrocarbons. The method is related to Faraday's discovery since hexachloroethane is generated and thermally decomposes.[1] Side products include carbon tetrachloride, hydrogen chloride, and hexachlorobutadiene.

Several other methods have been developed. When 1,2-dichloroethane is heated to 400 °C with chlorine, tetrachloroethene is produced by the chemical reaction:

ClCH2CH2Cl + 3 Cl2 → Cl2C=CCl2 + 4 HCl

This reaction can be catalyzed by a mixture of potassium chloride and aluminium chloride, or by activated carbon. Trichloroethylene is a major byproduct of the reaction, and since both are salable commercial chemicals, typical industrial practice is to collect both products and then separate them by distillation.

Uses

Most tetrachloroethylene is consumed as a solvent used in dry cleaning. It is desirable because it dissolves many organic materials, it is volatile, highly stable, and nonflammable. Usually as a mixture with other chlorocarbons, it is also used to degrease metal parts in the automotive and other metalworking industries. It appears in a few consumer products including paint strippers and spot removers.

It is used as a solvent for proton NMR spectroscopy.

Historical applications

Tetrachloroethene was also extensively used as an intermediate in the manufacture of HFC-134a and related refrigerants. In the early 20th century, tetrachloroethene was the most effective available treatment for hookworm.

Health and safety

Like many chlorinated hydrocarbons, tetrachloroethene is a central nervous system depressant, and inhaling its vapors (particularly in closed, poorly ventilated areas) can cause dizziness, headache, sleepiness, confusion, nausea, difficulty in speaking and walking, unconsciousness, and death.[2]

After repeated or extended skin contact, tetrachloroethene may dissolve fats from the skin, resulting in severe skin irritation in work environments where people have been exposed to high concentrations.

Tetrachloroethene is a common soil contaminant. Such contamination most often results from spillage, overfilling, sewer leakage, or the illegal disposal into UIC wells (e.g. septic systems, drywells) at commercial dry cleaning facilities. Because of the mobility of PCE in groundwater, its toxicity at low levels, and its density (which causes it to sink below the water table), cleanup activities tend to be especially problematic compared to cleanups of oil spills.

In industry, most workers are exposed to levels lower than those causing obvious nervous system effects. The health effects of tetrachloroethene at levels typically encountered in occupational or environmental exposures have not been well established.

Results from some studies suggest that women who work in dry cleaning industries where exposures to tetrachloroethene can be high may have more menstrual problems and spontaneous abortions than women who are not exposed. However, it is not known if tetrachloroethene was responsible for these problems because other possible causes were not considered.[citation needed]

Results of animal studies, conducted with amounts much higher than those that most people are exposed to, show that tetrachloroethene can cause liver and kidney damage. Exposure to very high levels of tetrachloroethene can be toxic to the unborn pups of pregnant rats and mice. Changes in behavior were observed in the offspring of rats that breathed high levels of the chemical while they were pregnant.

The International Agency for Research on Cancer has classified tetrachloroethene as a Group 2A carcinogen, which means that it is probably carcinogenic to humans.[3]

Testing for exposure

One method of testing for tetrachloroethene exposure is to measure the amount of the chemical in the breath, much the same way breath-alcohol measurements are used to determine the amount of alcohol in the blood. Because it is stored in the body's fat and slowly released into the bloodstream, tetrachloroethene can be detected in the breath for weeks following a heavy exposure.

Tetrachloroethene and trichloroacetic acid (TCA), a breakdown product of tetrachloroethene, can be detected in the blood. These tests are relatively simple to perform. These tests are not available at most doctors' offices, but can be performed at laboratories with the necessary equipment. Because exposure to other chemicals can produce the same breakdown products in the urine and blood, the tests for breakdown products cannot determine if one has been exposed to tetrachloroethene or the other chemicals.

References

  1. ^ a b M. Rossberg et al. “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06 233.pub2
  2. ^ Chemicals In The Environment: Perchloroethylene (Cas No. 127-18-4),U.S. Environmental Protection Agency, August 1994
  3. ^ IARC monograph. "Tetrachloroethylene" Vol. 63, p. 159. Last Updated May 20, 1997. Last retrieved June 22, 2007.

Further reading

  • Doherty, R.E. (2000). "A History of the Production and Use of Carbon Tetrachloride, Tetrachloroethylene, Trichloroethylene and 1,1,1-Trichloroethane in the United States: Part 1 - Historical Background; Carbon Tetrachloride and Tetrachloroethylene". Journal of Environmental Forensics 1: 69–81. doi:10.1006/enfo.2000.0010. 

External links


 
 

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Encyclopedia of Public Health. Encyclopedia of Public Health. Copyright © 2002 by The Gale Group, Inc. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Tetrachloroethylene" Read more