Global Stratospheric Ozone Reduction - Air Pollution and Global Warming: History, Science, and Solutions - page 247

by replacing two chlorine atoms in carbon tetrachloride
with two fluorine atoms. CFCs can also be obtained by
replacing all hydrogen atoms in methane [CH 4 (g)] or
ethane [C 2 H 6 (g)] with chlorine and/or fluorine atoms.

used for military personnel to spray insecticide to kill
malaria-containing bugs. In 1943, two researchers in
the U.S. Department of Agriculture responding to the
call, Lyle Goodhue and William Sullivan ,developed
amethod of propelling the insecticide as an aerosol
through the nozzle of a small can by liquefying CFC-
11 and -12. CFCs flowed out of the spray can's nozzle,
evaporating in the process and carrying with them a
mist containing other ingredients.
Spray cans were subsequently used as propellants
not only of insecticide, but also of hair spray, paint,
deodorant, disinfectant, and polish. In 1949, Robert
Abplanalp invented a method to discharge liquids from
aspray can under high pressure of a CFC gas. This
led to the widespread use of spray cans ejecting liquid
foams, powders, and creams together with the emission
of the CFC gas. When CFC use in spray cans was even-
tually banned, the replacement compound was com-
monly a mixture of volatile organic compounds selected
among propane, n-butane, isobutene, dimethyl ether,
and methyl ethyl ether, which are all more flammable
than CFCs.
CFC-11 and -12 have also been used as blowing
agents in foam production. A blowing agent is a volatile
compound added in small quantities as a liquid to
a chemical mixture containing polyurethane. As the
blowing agent evaporates, it causes the polyurethane
to expand, producing foam bubbles containing the gas.
Foam is used in insulation, disposable cups and cartons,
and fire extinguishers. CFCs are released to the air dur-
ing foam production; however, CFCs in the air spaces of
foam are usually confined and not an important source
of atmospheric CFCs.
Figure 11.12 shows the reported sales of CFC-11 and
-12 between 1976 and 2003. In 1976, almost 58 percent
of CFC-11 and -12 were sold for use as propellants in
spray cans. Secondary use of CFC-11 was as a blowing
agent and of CFC-12 was as a refrigerant. The large
decreases in the sales of CFC-11 and -12 in Figure 11.12
are due to regulation (Section 11.10). Black market
sales, though, continue to this day.
Table 11.2 lists additional CFCs. Of note, CFC-113
wasfirst produced in 1934 and used in air conditioning
units. It was subsequently used as a solvent in the micro-
electronics industry and in the dry cleaning industry, as
well as a spray can propellant and a blowing agent in
foam production.

11.5.1.1. Invention of Chlorofluorocarbons
The first CFCs were synthesized during the 1890s by
the Belgian scientist, Frederic Swartz (1866-1940). He
developed a method to produce CFCl 3 (g) and CF 2 Cl 2 (g)
by replacing one or two chlorine atoms with a fluorine
atom in CCl 4 (g). However, these compounds were not
used for practical purposes for several decades.
On a Saturday in 1928, a representative of General
Motors' Frigidaire division asked Thomas Midgley to
find a nontoxic, nonflammable substitute for an exist-
ing refrigerant, ammonia, a flammable and toxic gas.
The same afternoon, Midgley and his assistants, Albert
L. Henne (1901-1967) and Robert R. McNary (1903-
1988), working at the Thomas and Hochwalt Labora-
tory, 127 North Ludlow Street, Dayton, Ohio, hypoth-
esized that CF 2 Cl 2 (g) had the necessary qualities to
replace ammonia. They subsequently developed a more
efficient method of synthesizing it than did Swartz.
CFC-12 and subsequent CFCs were inexpensive,
nontoxic, nonflammable, nonexplosive, insoluble, and
chemically unreactive under tropospheric conditions.
As a result, they became popular. Midgley demonstrated
the nontoxic and nonflammable properties of CFC-12
to the American Chemical Society in April 1930, by
inhaling CFC-12 and then blowing it over a candle
flame, extinguishing the flame. The use of CFC-12 for
refrigeration was not disclosed previously because the
Frigidaire department of General Motors needed time
to file patents on the family of CFC compounds that
would be used for refrigeration (Bhatti, 1999). Midgley
is the same scientist who invented tetraethyl lead (ethyl)
as an additive to gasoline (Section 3.6.9). Some argue
that Midgley's chemical products led to the two greatest
environmental disasters of the twentieth century.
In 1931, CFC-12 wasproduced by the DuPont chem-
ical manufacturer under the trade name Freon ,aname
chosen by Midgley and his assistants. Its first use was
in small ice cream cabinets. In 1934, it was used in
refrigerators and whole-room coolers. Soon after, it
wasused in household and automotive air condition-
ing systems. In 1932, CFC-11 [CFCl 3 (g), trichloroflu-
oromethane] was first produced. Its first use was in
large air conditioning units. CFCs became airborne only
when coolants leaked or were drained.
During World War II, the U.S. government funded
research to develop a portable device that could be

11.5.1.2. Other Chlorine Compounds
CFCs are a subset of chlorocarbons ,wh ch

are compounds containing carbon and chlorine.