Thomas Midgley, Jr., introduced dichlorodifluoro- methane as a safe refrigerant gas for domestic refrigerators, leading to rapid growth in the acceptance of refrigerators in homes.
The growing availability of reliable refrigerators, freezers, and air conditioners had major impacts on the way Americans lived and worked as the twentieth century progressed. People could live more comfortably in hot and humid areas. Greater varieties of perishable foods could be transported and stored for extended periods. As recently as the early nineteenth century, the foods most regularly available to most Americans were salted meats and bread. Vegetables, fruits, and dairy products—items now considered essential to a balanced diet—were produced, purchased, and consumed only in small amounts. Commercial refrigeration became a necessity and a reality in the United States during the nineteenth century, when the population became concentrated in towns and cities. Through the early part of the twentieth century, the pattern of food storage and distribution evolved to make perishable foods more available. Farmers shipped dairy products and frozen meats in mechanically refrigerated railroad cars or in refrigerated ships. Wholesalers had large mechanically refrigerated warehouses. Smaller stores and most American households used iceboxes to keep perishable foods fresh. The iceman, who delivered large blocks of ice regularly, was a familiar figure on the streets of American towns.
Thomas Midgley, Jr.
In 1930, domestic mechanical refrigerators were still relatively uncommon, although they were being produced in increasing numbers. Most of them were vapor compression machines, in which a gas was compressed in a closed system of pipes outside the refrigerator by a mechanical pump and condensed to a liquid. The liquid was pumped into a sealed chamber in the refrigerator and allowed to evaporate to a gas. This evaporation cooled the interior of the refrigerator.
The major mechanical problems in designing an efficient home refrigerator had been solved by 1930; small and quite efficient electric motors had been developed to power the compression cycle, and compact and reliable automatic temperature controllers had become available. The remaining source of difficulty was the material constituting the working gas of the refrigerator. This gas had to have particular properties: It had to boil at a fairly low temperature, preferably between about –1.1 degrees Celsius and 4.4 degrees Celsius, and had to have an appropriate heat of vaporization—meaning that, in its evaporation from liquid to gas inside the sealed chamber of the refrigerator, it had to abstract a reasonable amount of heat energy from the inside of the refrigerator.
The gases in use in domestic refrigerators in 1930 included ammonia, sulfur dioxide, and methyl chloride. These gases were acceptable if the refrigerator’s gas pipes never sprang a leak. In actual operation of refrigerators, however, leaks sometimes occur; at such times, these refrigerant gases posed serious problems because all were toxic. Ammonia and sulfur dioxide both had unpleasant odors; if they leaked, at least they would be detected rapidly. Methyl chloride could form a dangerously explosive mixture with air, and it had only a very faint, and not unpleasant, odor. In a hospital in Cleveland during the 1920’s, a refrigerator with methyl chloride leaked, resulting in a disastrous explosion of the methyl chloride/air mixture. After that, methyl chloride for use in refrigerators was mixed with a small amount of a powerfully unpleasant-smelling compound to make leaks detectable. (The same method is used today with natural gas.)
General Motors, through its Frigidaire
Midgley’s chemist associates Albert Leon Henne and Robert McNary
Only a few such compounds had been reported; the Belgian chemist Frédéric Swarts had done pioneering basic research on them in the late nineteenth and early twentieth centuries, but no applications had resulted. Midgley, Henne, and McNary worked with Swarts’s data and concluded from their calculations that dichlorodifluoromethane, a compound whose molecules each contain one carbon atom, two chlorine atoms, and two fluorine atoms, should have ideal thermal properties and the right boiling point for a refrigerant gas. The great unknown was the toxicity of such a compound; they would have to prepare it in order to test it.
Preparation of the compound involved reaction between carbon tetrachloride (a common solvent used, at that time, in the dry-cleaning industry) and antimony trifluoride. The chemists prepared a few grams of dichlorodifluoromethane and put it, along with a guinea pig, into a closed chamber. They were delighted to see that the animal seemed to suffer no ill effects at all and was able to breathe and move normally. They were briefly puzzled when a second batch of the compound, made with another sample of antimony trifluoride, killed a second guinea pig almost instantly, but soon they discovered that an impurity in the antimony trifluoride had produced a potent poison in the refrigerant gas. A simple washing procedure completely removed the poisonous contaminant.
Experiments confirmed their calculations: Dichlorodifluoromethane was ideally suited to be a refrigerant gas, being nontoxic, nonflammable, and possessing excellent thermal properties. Its boiling point of –5.6 degrees Celsius was in the required range. This astonishingly successful research project was completed in three days. A few months later, Midgley announced the discovery at a meeting of the American Chemical Society held in Atlanta, Georgia, in April, 1930. When Midgley was awarded the Perkin Medal for industrial chemistry in 1937, he gave the audience a graphic demonstration of the properties of dichlorodifluoromethane. He inhaled deeply of its vapors and exhaled gently into a jar containing a burning candle. The candle flame promptly went out. This provided visual evidence that dichlorodifluoromethane was not poisonous and would not burn.
In order to produce the new refrigerant in commercial quantities, General Motors arranged to form a new company with Du Pont, which was the established supplier of sulfur dioxide to Frigidaire. The new product, dichlorodifluoromethane, was given the shorter trademarked name of Freon. The Du Pont laboratories undertook extensive toxicity testing, the results of which confirmed the safety of Freon, and Kinetic Chemicals arranged with the Interstate Commerce Commission to allow interstate transport of Freon and anhydrous hydrogen fluoride, which was needed to make Freon in large quantities. Within a year of the original discovery by Midgley and his associates, Freon was being manufactured and shipped not only to Frigidaire but also to most other major manufacturers of refrigeration and air-conditioning equipment.
Because of its desirable properties, Freon quickly became the preferred refrigerant gas for refrigerators and air conditioners. The availability of this safe refrigerant gas gave a major impetus to the production and sale of small and medium-sized refrigerators and freezers; it led to the patterns of food production, distribution, and consumption that became standard in the late twentieth century.
Air-conditioning
Dichlorodifluoromethane was later designated “Freon 12” to distinguish it from other chlorofluorocarbons.
In 1974, scientists began to ask whether there might be a serious effect on the environment from the release of chlorofluorocarbons into the air. They speculated that, because these compounds were so unreactive, they would persist and slowly migrate into the stratosphere, where they might be decomposed by the intense ultraviolet light from the Sun, which does not reach Earth’s surface because it is absorbed by a thin, but vital, layer of ozone
Impressed by the plausibility of these arguments, the Environmental Protection Agency banned the use of chlorofluorocarbons as aerosol propellants in the United States in 1978. They are being used still as refrigerant gases and as blowing agents for foamed plastics. International conferences on the environmental effects of chlorofluorocarbons have been held, and the major industrial nations have agreed to stop producing chlorofluorocarbons that are believed to affect the ozone layer. Chemical manufacturers have worked to develop alternative refrigerant gases that are slightly broken down by sunlight in the lower portions of the atmosphere so that they will not survive to interfere with ozone in the stratosphere.
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Anderson, Oscar Edward. Refrigeration in America. Princeton, N.J.: Princeton University Press, 1953. Valuable survey of the history of refrigeration in the United States devotes eight chapters to changes between the pre- and post-Freon eras. -
Benarde, Melvin A. Our Precarious Habitat: Fifteen Years Later. New York: John Wiley & Sons, 1989. Assesses environmental risk factors, including chlorofluorocarbons, and their potential impact on human health. Presents a reasonably balanced, nontechnical discussion. -
Christie, Maureen. The Ozone Layer: A Philosophy of Science Perspective. New York: Cambridge University Press, 2001. Presents the history of human knowledge about stratospheric ozone in a manner accessible to lay readers. Includes brief discussion of the impact of refrigerants on the ozone layer. -
Haynes, Williams. “Thomas Midgley, Jr.” In Great Chemists, edited by Eduard Farber. New York: Interscience, 1961. Detailed biography of Midgley by a major contributor to the history of industrial chemistry in the United States. Includes accounts of Midgley’s life and of his major discoveries. -
Parson, Edward A. Protecting the Ozone Layer: Science and Strategy. New York: Oxford University Press, 2003. Comprehensive technical discussion of efforts to protect the ozone layer undertaken through international cooperation. Includes information about refrigerants. -
Schufle, Joseph A. “Thomas Midgley, Jr.” In American Chemists and Chemical Engineers, edited by Wyndham D. Miles. Washington, D.C.: American Chemical Society, 1976. Brief biography of Midgley focuses on his chemical discoveries and training. -
Spiro, Thomas G., and William M. Stigliani. Environmental Issues in Chemical Perspective. Albany: State University of New York Press, 1980. Presents a moderately technical, balanced view of the chlorofluorocarbon problem. -
Thevenot, Roger. A History of Refrigeration Throughout the World. Translated by J. C. Fidler. Paris: International Institute of Refrigeration, 1979. Broad overview of refrigeration worldwide, with major sections on the changes brought about by the introduction of Freons.
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