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Fall 2010 | Volume 25 |  Issue 3

Before 1930, refrigerators were not only bulky and expensive but extremely dangerous. Chemicals used as refrigerants—ammonia, methyl chloride, and sulfur dioxide—were not only toxic but highly combustible. In 1929 a leak in a methyl chloride refrigeration system caused an explosion that killed more than 100 people in a Cleveland hospital. It was no wonder that consumers preferred their old iceboxes. That would all change in 1930 with the invention of Freon by a General Motors researcher.

At the end of World War I, GM had bought the Frigidaire Corporation, but it had not proved a lucrative investment. It lost $2.5 million in 1921, a year when only 5,000 refrigerators were built in the United States, of which just 365 were Frigidaires. As the decade wore on, Frigidaire became modestly successful, but Charles Kettering, GM’s research chief, knew that finding an improved refrigerant would determine Frigidaire’s future success. A nontoxic and nonflammable refrigerant might also produce dividends in the nascent field of air conditioning. At the time, artificial cooling was reserved for the occupants of a few large public buildings and a handful of wealthy homeowners.

Kettering, famous for creating the automobile self-starter, the high-compression engine, and the modern diesel locomotive, had spent the past decade working with mechanical engineer Thomas Midgley Jr. at Dayton Research Laboratories, a subsidiary of GM, on trying to improve the notoriously inefficient early gasoline engine. Encouraged by Kettering, Midgley had developed tetraethyl lead gasoline (TEL), which silenced engine “putt-putt” and “ping” sounds, eliminated sputtering, and helped prevent the overheating that often occurred when a motorist accelerated or climbed a hill. Their collaboration proved a big success, although tainted by claims that leaded gasoline was poisonous.

Kettering tasked Midgley with developing a new refrigerant, although the Cornell-trained engineer had taken only two formal chemical courses in his life. Yet Kettering knew that Midgley had a quality that he called “intelligent ignorance”: an ability to think, coupled with an absence of preconception, that is the hallmark of truly innovative inventors.

“It took a whole Saturday afternoon to sell Midge on the idea that this was quite an important project,” recalled Kettering. Midgley dropped his work on synthetic rubber tires and turned to refrigerants. In the fall of 1928, at Ohio State University’s laboratories in Columbus, he started with the periodic table. A quick survey of known refrigerants revealed that all were compounds of hydrogen, carbon, nitrogen, oxygen, sulfur, and the halogens. Within this set of compounds, flammability decreased from left to right on the table, while toxicity decreased from bottom to top. The two trends pointed to fluorine as a promising candidate. These results surprised Midgley, because many of fluorine’s compounds are poisonous. Although sodium chloride is innocuous table salt, its cousins sodium fluoride and hydrofluoric acid are used as an insecticide and to dissolve glass, respectively. Yet the carbon-fluorine bond appeared to be particularly stable.

Midgley and GM chemist Albert Henne set about synthesizing compounds of carbon, fluorine, and other halogens or hydrogen. They tested each compound for boiling point, flammability, toxicity, and other physical properties. This research uncovered that dichlorodifluoromethane (CC12F2), later dubbed Freon 12 or simply Freon, had a boiling point in the middle of the desired range and was nontoxic and nonflammable. Its success led to a whole class of compounds known as chlorofluorocarbons (CFCs).

We hope you enjoyed this essay.

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