Ethylene glycol (ETH-uh-leen GLYE-kol) is clear, colorless,
syrupy liquid with a sweet taste. One should not attempt
to confirm the compound’s taste, however, as it is toxic. In
recent years, more than 4 billion kilograms (9 billion pounds)
of ethylene glycol has been produced in the United States
annually. The compound is used primarily as an antifreeze
and in the manufacture of a number of important chemical
compounds, including polyester fibers, films, bottles, resins,
and other materials.
Ethylene glycol was first prepared in 1859 by the
French chemist Charles Adolphe Wurtz (1817–1884).
Wurtz’s discovery did not find an application, however,
until the early twentieth century, when the compound was
manufactured for use in World War I (1914–1918) in the
manufacture of explosives and as a coolant. By the 1930s,
a number of uses for the compound had been found, and the
chemical industry began producing ethylene glycol in large
quantities.
The primary method of producing ethylene glycol
involves the hydration of ethylene oxide, a ring compound
consisting of two methylene (-CH2) groups and one oxygen
atom. Hydration is the process by which water is added to a
compound. The hydration of ethylene oxide is conducted at a
temperature of about 383F (195C) without a catalyst, or at
about 50C to 70C (122F to 158F) with a catalyst, usually a
strong acid, either process resulting in a yield of at least 90
percent of ethylene glycol.
Other methods of preparation are also available. For
example, the compound can be produced directly from synthesis
gas, a mixture of carbon monoxide and hydrogen; or by
treating ethylene (CH2=CH2) with oxygen in an acetic acid
solution using a catalyst of tellurium oxide or bromide ion.
One of the first major uses of ethylene glycol was as a
radiator coolant in airplanes. The compound actually made
possible a change in the design of airplanes. At one time,
plain water was used as the coolant in airplane radiators. The
faster the airplane flew, the greater the risk that its radiator
would boil over. Adding ethylene glycol to the water raised
the boiling point of the coolant and allowed airplanes to fly
faster with smaller radiators. This change was especially
useful in the construction of military airplanes used in
combat.
Ethylene glycol is still used extensively as a coolant and
antifreeze in cooling systems. It is also used as a deicing
fluid for airport runways, cars, and boats. Brake fluids and
shock-absorber fluids often contain ethylene glycol as protection
against freezing. About 26 percent of all the ethylene
glycol made in the United States is used for some kind of
cooling or antifreeze application.
The largest single use of ethylene glycol today is in the
manufacture of a plastic called polyethylene terephthalate
(PET). PET’s primary application is in the manufacture of
plastic bottles, an application that accounts for about a third
of all the ethylene glycol made in the United States. Large
amounts of PET are also used in the manufacture of polyester
fibers and films. Some additional uses of the compound
include:
• As a humectant (a substance that attracts moisture) in
keeping some food, tobacco, and industrial products
dry;
• As a solvent in some paints and plastics;
• In the dyeing of leathers and textiles;
• In the manufacture of printing inks, wood stains, ink
for ball-point pens, and adhesives;
• In the production of artificial smoke and fog for theatrical
productions;
• As a stabilizer in the soybean-based foam sometimes
used to extinguish industrial fires; and
• In the manufacture of specialized types of explosives.
Ethylene glycol poses a number of potential health and
safety hazards. It is very flammable and highly toxic. Ingestion
of the compound may cause nausea, vomiting, abdominal
pain, weakness, convulsions, and cardiac problems.
Higher doses can result in severe kidney damage that leads
to death.
