Mercury, a chemical element with the atomic number 80 is a transition metal. The most interesting fact about mercury is that though it is a heavy metal, it can exist in the liquid form at room temperature and pressure. It is a rare element found in the crust of the Earth, and it naturally occurs as cinnabar or mercuric sulfide.
Sometimes, it also occurs as livingstonite, corderoite, and other minerals, but it is rarely found as a native metal. In chemistry, it is represented by the symbol Hg, which comes from the Latin word hydrargyrum, which in turn is said to be derived from the Greek word hydrargyros, that means water and silver. True to its name, mercury occurs as a liquid with a silvery shine.
Uses of Mercury
No single scientist can be credited for discovering mercury, as it was familiar to many ancient civilizations. However, the French chemist Antoine-Laurent de Lavoisier is credited for distinguishing mercury as an element.
Mercury has been found in some Egyptian tombs, which are almost 3500 years old. For the Chinese and Tibetans, mercury was an element supposed to prolong life and heal fractures. For the ancient Greeks, it was an essential ingredient of ointments, while the ancient Egyptians and Romans used it in cosmetics. At one point, it captivated the minds of the alchemists, who considered it as the First Matter, from which all other matters could be obtained simply by varying the quality and quantity of sulfur.
Mercury is known to have seven stable isotopes. It can easily dissolve to form amalgams with many metals, including gold and zinc. However, it does not form amalgams with iron, due to which it can be stored in an iron flask. It is not a very active element in the sense that, it does not react easily, and for this reason mercury is considered as a noble metal, along with gold, silver, and platinum. But when heated, it reacts with oxygen to produce mercuric oxide.
Mercury and many of its compounds have been used traditionally for varied purposes. For example, mercury (I) chloride and mercury (II) sulfide were (and still are) used in medicine, and as vermilion (a red pigment). The traditional practice of using mercury for extracting gold and silver has however, declined substantially. Mercury (II) chloride was also used in the past to treat syphilis.
It has been used in thermometers, barometers, sphygmomanometers, manometers, and many other scientific instruments. However, because of its toxicity, some of these apparatus are now being replaced with alcohol-filled or digital instruments. Mercury is also used as an amalgam in dentistry, while mercury fulminate is used as a detonator in explosives.
Thiomersal is a mercury compound, which is used in manufacturing mascara, and as a preservative in vaccines. Merbromin is another mercury compound, which is used as an antiseptic for topical use. Mercury is also used in fluorescent lamps, mercury vapor lamps, gaseous electron tubes, batteries, liquid-mirror telescopes, etc.
Volcanoes are the source of almost half of the atmospheric mercury, while the rest comes from human activities like coal power plants, gold production, production of non-ferrous metals, caustic soda production, disposal of wastes, and production of batteries, pig iron, and steel.
Mercury is a highly toxic metal, when inhaled or ingested. Many of its compounds are also poisonous, of which dimethylmercury and methyl mercury are the most toxic of all. Methyl mercury, which is soluble in water, can accumulate in high concentrations in many fish and shellfish. Consumption of such fish can increase the level of mercury in the body, and eventually cause mercury poisoning.
Methyl mercury has the potential to cause permanent damage to the brain and the kidneys. It has been found to be harmful for fetal development. Its ingestion is supposed to weaken the immune system. Considering the health and environmental hazards associated with mercury and mercury compounds, their use has been brought under the control of various regulations in many countries, including the United States and countries of the European Union.