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The first chlorofluorocarbon compound they synthesized was dichlorodifluoromethane (CCl2F2), known as F12 and sold under the proprietary name Freon, whose intermediate was trichlorofluoromethane (CFCl3 known as F11), and although they did not make it, they were aware that they could also produce the overfluorinated alternative, chlorotrifluoromethane (CF3Cl), known as F13. They sniffed F12 and survived the experiment; then they organized a series of guinea pig tests proving the compound’s safety. In April 1930 Midgley introduced Freon at the American Chemical Society meeting in a surprising manner, inhaling a bit of it on stage (nontoxic!) and slowly exhaling it to distinguish a candle flame (nonflammable!). In August 1930 GM and DuPont set up a joint stock company to make and market the compound, and Freon received its US patent (under the generic title Heat transfers) in November 1931.
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