What is Mercury?

Mercury is a metallic element with the atomic number 80 and the symbol Hg, from the Latin hydragyrus, which means “liquid silver.” On the periodic table of elements, it is found in Group 12, just below cadmium, and in Period 6 between gold and thallium. It is referred to as a “transition metal.” It is a heavy element that is liquid at room temperature. Described as silvery-white in color, it is poisonous.

Scientists don't know who discovered mercury, but it was already recognized in ancient times. The extraction process was first described by the Greek philosopher Aristotle (384–322 B.C.). Its name, for the Roman god Mercury, reflects that time period.

This element is often obtained from cinnabar ore. The process by which the vapor is extracted from cinnabar ore is called roasting. It is then condensed in order to collect it in liquid form. Mercury is found mainly in Europe — in Spain, Italy, and the area that was formerly Yugoslavia. About 8,400 tons (7,620 metric tons) per year are produced.

Mercury has a number of uses. It is the customary liquid in thermometers as well as barometers and sphygmomanometers, and it is used in esophageal dilators, batteries, paint, plastics, and pesticides. Its vapor is also used in lamps, and the element is used in the gold mining industry.

This liquid metal is highly toxic. It is associated with birth defects in children and with neurological damage, kidney damage, and blindness upon later exposure.

Today, contaminated fish is one of the main sources of mercury exposure outside of industry. In times past, the element was used in the manufacture of felt hats. Mercury poisoning was, therefore, an occupational hazard of a hatter, leading to the phrase “mad as a hatter” and to the character of the Mad Hatter in Alice’s Adventures in Wonderland by Lewis Carroll, the pen name of Charles Lutwidge Dodgson.

Mercury does have some health uses, however. Its inorganic salts are components of some products that stem the growth of bacteria and fungi. It is also used in hospital labs in urine analysis and in fixatives.