In response to a growing need for such chemicals, the Du Pont Corporation introduced a class of nontoxic, nonflammable chemicals called chlorofluorocarbons for use as refrigerants, which they trademarked under the name Freon. Despite the advance in health and safety that Freon seemed to represent, it later was shown to harm the earth’s ozone shield, potentially creating a greater long-term hazard than did the more toxic chemicals it replaced.

The history of mechanical refrigerators can be traced to the late eighteenth century, but the earliest devices relied on steam power and were large and cumbersome. Nevertheless, some refrigerators were used for ice-making and for industrial cooling in the nineteenth century. The source of the cooling effect was the evaporation of a volatile substance (the “refrigerant”) in a closed system. The evaporation cooled saltwater or air that circulated around the outside of the closed system. In order to achieve continuous cooling, the refrigerant would be reliquefied by a compressor, with the accompanying heat being rejected to the outside through air cooling. In effect, the refrigerator acted to pump heat from the interior of the unit to the outside, causing its surroundings to become warmer and creating a cold zone inside. [kw]Du Pont Introduces Freon (Dec., 1930)
[kw]Freon, Du Pont Introduces (Dec., 1930)
Inventions;Freon
Freon
Du Pont Corporation[Dupont Corporation];Freon
Chlorofluorocarbons
Refrigeration
[g]United States;Dec., 1930: Du Pont Introduces Freon[07700]
[c]Environmental issues;Dec., 1930: Du Pont Introduces Freon[07700]
[c]Inventions;Dec., 1930: Du Pont Introduces Freon[07700]
[c]Science and technology;Dec., 1930: Du Pont Introduces Freon[07700]
[c]Earth science;Dec., 1930: Du Pont Introduces Freon[07700]
Midgley, Thomas, Jr.
Kettering, Charles Franklin
Henne, Albert Leon
Rowland, F. Sherwood
Stolarski, Richard

Household refrigerators became practical after electricity and small electrical motors became available, eliminating the need for steam power. In 1913, the first home refrigerator went on sale in the United States. Household appliances;refrigerators It used sulfur dioxide as a refrigerant, but it required the owner to keep a compressor in the cellar; the compressor would be connected by tubes to an icebox upstairs in the kitchen. This arrangement was considered necessary because of the possibility of leakage of obnoxious fumes from the compressor. In the 1920’s, some household refrigerators appeared in which ammonia—a toxic, flammable substance—was used as a refrigerant. These appliances were successful enough to show that an enormous potential market existed, but it was necessary for manufacturers to achieve greater safety and reliability before refrigerators could become commonplace.

In response to this need, Charles Franklin Kettering, an executive at General Motors Corporation, asked Thomas Midgley, Jr., an engineer, to look into the development of a safe, effective refrigerant for use in consumer products. After talking to Lester Keilholtz, the chief engineer at the Frigidaire Corporation, Midgley went to work in the library, along with coworkers Albert Leon Henne and Robert MacNary. MacNary, Robert They became familiar with the physical and chemical properties of the known useful refrigerants described in chemical and engineering literature. All such materials contained one or more of the elements carbon, hydrogen, oxygen, or nitrogen, elements that occur in the first part of the chemist’s periodic table. The element fluorine, adjacent to oxygen in the periodic table, was known to form many compounds with low boiling points that might be suitable refrigerants. The possible toxicity of such compounds was of concern, however, as several fluorine compounds, such as hydrogen fluoride, are hazardous to breathe.

At the time of Midgley’s work, organic fluorine compounds were not yet available commercially, but they could be made in the laboratory by fluorination procedures worked out by the Belgian fluorine pioneer Frédéric Swarts. Swarts, Frédéric Swarts’s methods depended on the replacement of chlorine atoms in carbon-chlorine compounds by fluorine through the use of metal fluorides, such as antimony trifluoride, as fluorine carriers. Midgley obtained several bottles of antimony trifluoride, which he later described as probably the entire U.S. supply of the compound. He did not know that only one of the samples was pure and free of water. Fortunately, and quite by accident, the pure sample was used in the first fluorocarbon preparation and afforded a pure, nontoxic fluorocarbon, harmless to experimental animals. The less-pure antimony fluoride released toxic gases in addition to the desired fluorocarbon.

Encouraged by the preliminary experiment, Midgley and Henne made a thorough study of possible organic fluorides for use as refrigerants, and they published their findings in 1930. General Motors and the Du Pont Corporation formed a new company, Kinetic Chemicals, Kinetic Chemicals to manufacture dichlorodifluoromethane Dichlorodifluoromethane (Freon 12), and production began in December, 1930. The company trademarked the term Freon, which came to refer to a category of fluorocarbons or chlorofluorocarbons used as refrigerants, rather than to a particular chemical. During 1931, more than one million pounds of Freon 12 were sold. In 1935, a U.S. patent was granted to General Motors for the use of Freon as a refrigerant.

The increasing production and use of chlorofluorocarbons (CFCs) had many and diverse effects in the United States. An enormous increase in sales of home refrigerators began in the 1930’s and escalated after World War II. According to one source, there were 35 million households with refrigerators by 1950 and 51 million by 1960. The use of CFCs in these refrigerators made them more appealing to the consumer. Later, home and automobile air conditioners were also sold in vast numbers. The convenience and portability of these appliances resulted partly from the use of CFC refrigerants.

At major chemical companies such as Du Pont, chemists began to foresee other uses for CFCs. Soon, CFC solvents were developed and became increasingly important in electronic applications, such as the removal of grease from printed circuits. Volatile fluorocarbons and chlorofluorocarbons began to be used as aerosol propellants. Aerosol sprays
Propellants;aerosol sprays In this application, their low toxicity and lack of flammability gave them an advantage over such propellants as butane or nitrous oxide. Foam plastic manufacturers began to use fluorocarbon gases as “blowing agents” to create bubbles in plastic. Bromine-containing fluorocarbons were developed for use as fire-extinguishing materials such as Halon. As the uses of fluorocarbons expanded, more corporations began to manufacture them, not only in the United States but also in Europe and Japan. By 1969, production of fluorocarbons reached 700 million pounds, of which about half was dichlorodifluoromethane. By 1974, world production of fluorocarbons was almost 2 billion pounds. This expansion was not an unmixed blessing, as events were to show. The fluorocarbons, CFCs, Freons, and their chemical cousins that were being so copiously manufactured were ultimately escaping into the atmosphere.

In June, 1974, F. Sherwood Rowland and M. Molina published a paper in the British journal Nature describing the possible fate of CFCs in the earth’s atmosphere. They theorized that, after diffusing slowly into the stratosphere, CFCs would undergo irradiation by highly energetic ultraviolet light from the Sun. This radiation, upon absorption by a CFC molecule, would produce a temperature increase and, at the same time, would cause some CFC molecules to break up, forming highly reactive chlorine atoms. Earlier in 1974, Richard S. Stolarski and Ralph J. Cicerone had shown that chlorine atoms from rocket exhaust could cause ozone decomposition in the stratosphere.

The stratosphere, an atmospheric layer of about ten to fifty kilometers in altitude, is the site of the earth’s protective ozone layer. Ozone is a form of oxygen containing three oxygen atoms rather than the two atoms present in ordinary oxygen. Ozone exists at low pressures and is continually forming and decomposing under the influence of solar radiation and through encounters with other constituents of the atmosphere. Although ozone is highly irritating and toxic and is regarded as a threat to health when it occurs near the earth’s surface, it has at least two beneficial effects when in its proper concentration and location in the stratosphere: It absorbs potentially dangerous ultraviolet radiation that might otherwise penetrate to the earth’s surface, and it helps to regulate the temperature of the stratosphere.

Health effects of ultraviolet radiation include damage to skin and eyes, damage that can lead to skin cancer and cataracts. Although these effects are well known, it is difficult or impossible to predict the increased incidence of cancer or cataracts as a function of solar ultraviolet radiation. The effects are of a statistical nature, and many other environmental and hereditary factors may be involved in the incidence of such problems. Most scientists agree that degradation of the ozone layer presents a health hazard, but estimates of the magnitude of the threat vary widely.

The story of the CFCs has shown the importance of considering the long-term environmental effects of each new product, particularly those that are manufactured and discarded in large quantities. The unique international cooperation shown in response to the threat to the ozone layer has been based on the recognition that, as the atmosphere has no political boundaries, the rules to protect it must also transcend such distinctions. Inventions;Freon
Freon
Du Pont Corporation[Dupont Corporation];Freon
Chlorofluorocarbons
Refrigeration

• Benedick, Richard E. Ozone Diplomacy: New Directions in Safeguarding the Planet. Cambridge, Mass.: Harvard University Press, 1991. Presents the text and a list of signers of the Montreal Protocol of 1987 and a detailed account of the negotiations that led to it. Authored by the head U.S. negotiator.
• Biddle, Wayne. A Field Guide to the Invisible. New York: Henry Holt, 1998. Discussion of the practical effects of fifty-eight unseeable entities, including Freon. Other entities discussed range from radio waves to bad breath to God. Bibliographic references and index.
• Derra, Skip. “CFC’s: No Easy Solutions.” Research and Development 32 (May, 1990): 56-66. The applications of CFCs are discussed, and attempts to find replacements are outlined. Provides a list that shows the uses of individual CFCs and their effects on the ozone layer. Includes an account of steps being taken in various countries toward compliance with the Montreal Protocol.
• Gillespie, Alexander. Climate Change, Ozone Depletion, and Air Pollution: Legal Commentaries Within the Context of Science and Policy. Boston: M. Nijhoff, 2006. Extensive legal analysis of the chemical threat to the ozone layer, synthesizing scientific knowledge on the subject with policy analysis. Bibliographic references and index.
• Gribbin, John. The Hole in the Sky. Rev. ed. New York: Bantam Books, 1993. An introduction to the ozone shield and its problems. Describes the discovery of the Antarctic ozone hole.
• Midgley, T. M., Jr. “From the Periodic Table to Production.” Industrial and Engineering Chemistry 29 (1937): 241-244. Midgley gives a vivid account of the events leading up to the development of chlorofluorocarbon refrigerants. This account is either paraphrased or quoted from in most historical works that treat the subject.
• Midgley, Thomas, and A. L. Henne. “Organic Fluorides as Refrigerants.” Industrial and Engineering Chemistry 22 (May, 1930): 542-548. Originally read as a paper at a 1930 meeting of the American Chemical Society, this paper announces the development of CFCs as refrigerants.
• Roan, Sharon. The Ozone Crisis: The Fifteen-Year Evolution of a Sudden Global Emergency. New York: John Wiley & Sons, 1989. Follows the complicated story of the ozone crisis, starting from the Rowland-Molina publication of 1974. All the political maneuverings and scientific evidence are recounted in a historical-journalistic approach.
• Rowland, F. Sherwood. “Stratospheric Ozone in the Twenty-first Century: The Chlorofluorocarbon Problem.” Environmental Science and Technology 25 (April, 1991): 622-628. Clear, well-illustrated article that discusses the Antarctic ozone hole and the role of CFCs and ozone in the greenhouse effect.
• Schwartz, A. Truman, et al. Chemistry in Context. Dubuque, Iowa: William C. Brown, 1994. The first three chapters of this college-level chemistry book deal with the earth’s atmosphere. Discusses global warming and the effects of CFCs on the ozone layer. Basic scientific background for an understanding of atmospheric chemistry. Color illustrations and list of references.
• Stolarski, Richard S. “The Antarctic Ozone Hole.” Scientific American 258 (January, 1988): 30-36. Describes how ice crystals in stratospheric clouds may facilitate the breakdown of chlorine compounds, leading to ozone destruction. Considers whether the ozone hole of 1984 was an anomaly or whether such holes might reappear in the Antarctic and perhaps elsewhere.

Birdseye Invents Quick-Frozen Foods

Midgley Introduces Dichlorodifluoromethane as a Refrigerant Gas