What Is Tetrachloroethylene?
Tetrachloroethylene is a colorless liquid at room temperature.
It has a planar structure with the molecular formula C2Cl4 and a molecular weight of 165.83. The hydrogen group of ethylene is replaced by a chlorine group.
Its IUPAC nomenclature is tetrachloroethene (tetrachloroethylene), but other abbreviations include perchloroethylene (perchloroethylene), perc (perc), and PCE. It was first successfully synthesized in 1982 by Michael Faraday by heating hexachloroethane.
Properties of Tetrachloroethylene
1. Properties
Tetrachloroethylene has a melting point of -22°C, a boiling point of 121°C, and a specific gravity of 1.62 g/mL. It is miscible in many organic solvents, such as ethanol and acetone, but almost insoluble in water. Tetrachloroethylene has a viscosity of 0.84 cP (25°C) compared to water’s 0.89 cP (25°C). This heavier than water and more easily penetrated than water is the cause of deep and widespread soil and groundwater contamination.
It is nonflammable, but decomposes when exposed to hot surfaces or flames, producing toxic and corrosive gases (hydrogen chloride, phosgene, chlorine). When in contact with moisture, it gradually decomposes to produce trichloroacetic acid and hydrochloric acid.
2. Effects on the Human Body
Tetrachloroethylene evaporates easily into the air and has a sharp, sweet odor that is perceptible even at concentrations below 1 ppm. Like other halogenated hydrocarbons, it has a paralyzing effect on the central nervous system and should be handled with care. Inhalation of the vapors can cause dizziness, headache, drowsiness, and in severe cases, speech impairment, difficulty walking, unconsciousness, and even death.
Uses of Tetrachloroethylene
The primary use of tetrachloroethylene is as a solvent. Because it can dissolve most organic compounds and acts like an oil remover, it is often used for dry cleaning and for cleaning metal industrial products such as automobile parts. It is also used to clean movie films, for example. Other uses include as an intermediate in the manufacture of refrigerants such as HCFC-134a.
Tetrachloroethylene is used in a variety of locations, but poses a risk of soil contamination. It can also contaminate groundwater, so factories and other facilities must be careful when handling liquid waste.
Other Information on Tetrachloroethylene
1. Tetrachloroethylene Production Process
Tetrachloroethylene is produced from ethylene via 1,2-dichloroethane; heating 1,2-dichloroethane to 400°C in the presence of chlorine produces hydrogen chloride and tetrachloroethylene. The byproduct trichloroethylene is often separated, purified, and recovered by distillation because it is a useful compound.
Tetrachloroethylene can also be produced from partially chlorinated light hydrocarbons, which are waste products from other chemical synthesis processes. Heating these chlorohydrocarbons with excess amounts of chlorine yields a mixture of tetrachloroethylene, carbon tetrachloride, and hydrogen chloride.
Handling and Storage Precautions
Precautions for handling and storage are as follows:
- Keep containers tightly closed and store in a cool, dry and well-ventilated place.
- Use only outdoors or in well-ventilated areas.
- Do not inhale mists, vapors, or sprays.
- Wear protective gloves and eye protection when using.
- Remove gloves properly after use to avoid skin contact with this product.
- Wash hands thoroughly after handling.
- In case of skin contact, wash with soap and plenty of water.
- In case of eye contact, rinse cautiously with water for several minutes. If irritation persists, consult a physician.