1930

Chlorofluorocarbons

Charles Franklin Kettering (1876–1958), Thomas Midgley Jr. (1889–1944), Albert Leon Henne (1901–1967)

Few remember it now, but refrigerators used to be able to kill you. Virtually all commercial refrigeration units run on the cooling and heating cycle provided by the expanding and compressing of some working gas, but back in the 1920s, the choices for gases were a bit rough. Ammonia was widely used, as was sulfur dioxide, but both of those are quite toxic, not to mention corrosive to the refrigeration equipment itself. Propane was found in some models, but it is, of course, extremely flammable in the case of a leak. Something nonpoisonous and non-explosive was needed, and a General Motors research team under Charles Kettering was one of several looking at the possibilities.

American chemist Thomas Midgley Jr., the respected discoverer of tetraethyl lead, and his colleague, Albert Leon Henne, were put on the problem. They realized that halogenated carbon compounds had a lot to recommend them, since they were very hard to ignite. Even better, the smaller ones had convenient boiling points for refrigerant gases and were very compressible. The best properties were to be found in the compounds that mixed chloro- and fluoro-substituents, such as the nontoxic and noncorrosive dichlorodifluoromethane, which they first prepared in 1930. The company gave it the trade name Freon (later their base name for a whole series of similar compounds), and it was a hit. Soon it was being used as an inert propellant in spray cans and later in asthma medicine inhalers.

Midgley received many honors for his invention of chlorofluorocarbons (CFCs), including the distinguished awards named after English chemists Sir William Henry Perkin and Joseph Priestley, along with election to the National Academy of Sciences. No one realized yet the havoc CFCs were causing in the upper atmosphere, or the human costs tetraethyl lead was exacting closer to the ground. So although Midgley was an extremely successful and inventive research chemist, he may well have been the cause of more damage to the Earth’s atmosphere than any single human being in history. The extent of that damage was apparent only decades after his own death.

A young couple standing next to a refrigerator that must have looked quite modern at the time. With the round compressor on top, this refrigerator used either sulfur dioxide or methyl formate—both quite toxic—for cooling, but it would soon be replaced by a new breed using Freon.