(Chemical symbol Hg). Atomic number 80, Atomic weight 200.59, mp -38.84C, specific gravity 13.55. A silvery white metal that is liquid at room temperature. Mercury has been found in Egyptian tombs of 1500BC and was widely known in the centuries BC in China and India. The earliest extractions were carried out by roasting cinnabar, mercury II sulphide, in an oxidising atmosphere and collecting the mercury by distillation. Also known as 'quicksilver'.