Dichlorodifluoromethane and chlorodifluoromethane were widely used refrigerants. Dense gases such as xenon and dichlorodifluoromethane have low thermal conductivity. This reaction can also produce trichlorofluoromethane (CClF), dichlorodifluoromethane (CClF) and tetrafluoromethane (CF). The most common representative is dichlorodifluoromethane (R-12 or Freon-12). In 1930 Thomas Midgley, Jr. discovered dichlorodifluoromethane, a chlorinated fluorocarbon (CFC) known as freon. Dichlorodifluoromethane was one of the original propellants for Silly String. Dichlorodifluoromethane with argon can be used for protective atmosphere for melting of aluminium-lithium alloys. The team eventually synthesized dichlorodifluoromethane, the first chlorofluorocarbon (CFC), which they named "Freon". Their product was dichlorodifluoromethane and is now designated "Freon-12", "R-12", or "CFC-12".