Chlorofluorocarbon: Chlorofluorocarbon (CFC), any of several organic compounds composed of carbon, fluorine, and chlorine. When CFCs also contain hydrogen in place of one or more chlorines, they are called hydrochlorofluorocarbons, or HCFCs. CFCs are also called Freons, a trademark of the E.I. du Pont de Nemours & Company in Wilmington, Del. CFCs were originally developed as refrigerants during the 1930s. Some of these compounds, especially trichlorofluoromethane (CFC-11) and dichlorodifluoromethane (CFC-12), found use as aerosol-spray propellants, solvents, and foam-blowing agents.
The Egyptians started building the Great Pyramid of Giza on August 23, 2470 B.C., according to controversial new research that attempts to place an exact date on the start of the ancient construction project. Enlarge Photo. Printer Friendly. Email to a Friend.
Egyptian pyramid of Khufu. The largest Pyramid, King Khufu s, is often called the Great Pyramid. It lies in the desert west of Giza, accompanied by the pyramids of Khafre and Menkaure (Khufu s son and grandson). The Great Pyramid was built during Khufu s reign (2551 bc-2528 BC).ncient Egyptian Pyramids in Giza. Egyptian pyramids are great monument of a great civilization that was born seven thousand years ago. The ancient Egyptians built more than 90 royal pyramids, from about 2630 BC until about 1530 BC.