Mercury is a very poisonous metal that should never be handled. It is especially dangerous because of its attractive look as a shiny liquid that moves quickly, which makes humans touch it.
In the chemical table, mercury has the symbol Hg. This comes from hydrargyrum, the metal's name in Greek, meaning liquid silver due to mercury's shiny appearance. Quicksilver is another alternative name, also caused by the mobility of this liquid metal. Mercury has been discovered and used by humans since ancient times. Traces were detected in Egyptian tombs built 3500 years ago and there is evidence it was also used in ancient India and China.
This element is extremely poisonous and can enter the body by ingestion, inhalation or direct contact with an open wound. It causes many serious symptoms, in particular kidney and liver damage as well as the destruction of nerves.
Mercury has a number of industrial uses, despite its well-known toxicity. It is most commonly found today in the production of new types of compact fluorescent light bulbs. These modern light sources are based on a mixture of chemical compounds, including mercury vapours. It is also included in some doze alarm clocks, as well as the switches of thermostats, because it conducts electricity well.
In the periodic table, mercury is listed as the third element of the twelfth column, part of the group of so-called transition metals. The most common isotope of mercury has 122 neutrons, 80 electrons and 80 protons.
Of all known metals, mercury is the only that is always liquid in normal temperature and pressure conditions. Bromine is also liquid in such and environment, but it is not a metal but a halogen. Three other metals, gallium, rubidium and cesium, melt at a slightly higher temperature. Mercury forms spherical liquid drops, due to the very high tension on its surface.
Mercury has been considered for a long time to provide health benefits and it was used in various treatments. It is known today that both the pure metal and all of its compounds are extremely dangerous.
Even if it has been discovered early, this element is rarely found on Earth. Only 0.08 parts per million of the Earth’s crust consist of mercury. The best source is cinnabar, which is a mercury sulphide mineral that is also used to produce vermillion, a red pigment.
Mercury reacts with aluminum, so it is not allowed on airplanes because it could alter their metallic structure. When combined with aluminum, mercury forms an amalgam. As a result, it destroys the oxide layer that prevents aluminum from reacting with air. Aluminum then starts to oxidize, a similar process to the rust that develops on iron. However, most acids are unable to dissolve mercury.
Even if most other metals are good heat conductors, mercury is pretty poor at this task. It is also an average conductor of electricity. It has an interesting property: the difference between the freezing point (-38.8 degrees Celsius) and boiling point (356 degrees Celsius) is the smallest of any metal.
The normal oxidation state of mercury is either +1 or +2. However, a state of +4 is also possible in some cases. Mercury resembles the so-called noble gases because of its particular electron configuration. This makes reactions with other elements difficult and the chemical bonds formed tend to be very weak. When combined with most metals, with the exception of iron, it forms amalgams. As a result, the containers used to transport mercury are made of iron.
The common name of mercury dates from the era of alchemists and comes from the ancient Roman god Mercury. While all other names lost their alchemical names, mercury still retains it.
High levels of toxic mercury can accumulate in the tissues of some species of predator fish like the shark and swordfish. It is banned in industry in some countries in Scandinavia, due to the dangerous toxic effects.
Hat makers inhaled mercury vapours from the mix of chemicals used in their trade. As a result, they often became insane, which explains the expression "mad as a hatter". Mercury can poison you by permeating the skin, so never handle it. It can also evaporate and produce toxic fumes, so it should never be left in the open, in order to avoid air contamination.
Humans can absorb this toxic metal by eating food that contains it, as well as through skin absorption or inhalation. Mercury is very dangerous and large doses are fatal.
Mercury dissolves other metals when it comes in contact with them; the result is a substance with different chemical properties known as an amalgam. Iron is the only metal that resists this reaction.
The most common isotope of mercury, about 30% of the total amount found on Earth, is Mercury-202. However, there are six other stable isotopes that occur naturally.
In the Earth's crust mercury is very rare but can still be found sometimes in pure form. However, it is most abundant as part of cinnabar, livingstonite, corderoite and other ores. Cinnabar, known since ancient times for its vivid red color, is the mercury ore commonly used to produce it.
Italy and Spain are the traditional countries that extract and refine mercury. Spain operated major silver mines in South America, which needed important amounts of mercury. However, China and Kyrgyzstan are today the main exporters of this metal.
Mercury has been discovered since ancient times. The ancient Egyptians and Chinese, as well as other civilizations, were able to extract and use it. Qin Shi Huang, the emperor who united China, was killed after he ingested this very toxic metal. It was one of the ingredients of an Elixir of Life that he believed it could grant him immortality.
Alchemists were convinced that mercury could be used to produce gold. In alchemy, mercury was thought to be the "prima materia" that could be transmuted into all other metals, including precious ones.
Mercury has many possible uses but it is being replaced with alternative materials due to its toxicity. It has been used for a long time in thermometers, barometers and other instruments of measure, because it expands with temperature and has a very high density. Mercury vapour lamps, fluorescent lamps and other light sources are today the main items that include mercury. It's also found in various other applications, such as telescopes, dental materials and even vaccines or cosmetics.
Even if it is a metal, mercury is liquid at normal room temperature. It is not only very toxic but it also builds up in the body, causing long-term damage. The symptoms of mercury poisoning appear after minor exposure, while larger doses cause serious kidney, lung and brain damage. It is still used in industry, despite the risks.
Blood pressure monitors and thermometers have been traditionally made using mercury. It is being phased out today, as safer technologies based on non-toxic materials are being developed. The amalgam fillings used by dentists to patch cavities still have a content of about 50% mercury.
One compound of mercury, known as Thiomersal or Thimerosal, is a preservative widely used in the pharmaceutical industry. It is mainly found in vaccines but also in the composition of antiseptic and diaper rash ointments, nasal sprays and eye drops. It is also common in various brands of mascara, as well as tattoo inks.
An alternative to the widespread neon lights can be produced using mercury and used for advertising purposes. Modern fluorescent lamps include this metal in their structure. Mercury is needed for the chemical processes that result in caustic soda and chlorine.
This metal has many other uses, for example the manufacturing of liquid mirrors, medical devices or float valves, as well as the production of other elements. For a long time, mercury fulminate has been one of the most common explosives.