Mercury

Mercury, also known as quicksilver , is a chemical element with the symbol Hg (Latinized Greek: hydrargyrum, from "hydr-" meaning watery or runny and "argyros" meaning silver) and atomic number 80. Mercury is the only metal that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine. With a freezing point of −38.83 °C and boiling point of 356.73 °C, mercury has one of the broadest ranges of its liquid state of any metal. A heavy, silvery d-block metal, mercury is also one of the five metallic chemical elements that are liquid at or near room temperature and pressure,the others being caesium, francium, gallium, and rubidium.

Mercury was used for fire gilding and silvering of cultural heritage objects.

History
Mercury was found in Egyptian tombs that date from 1500 BC.

In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. One of China's emperors, Qín Shǐ Huáng Dì — allegedly buried in a tomb that contained rivers of flowing mercury on a model of the land he ruled, representative of the rivers of China — was killed by drinking a mercury and powdered jade mixture (causing liver failure, poisoning, and brain death) intended to give him eternal life.

The ancient Greeks used mercury in ointments; the ancient Egyptians and the Romans used it in cosmetics which sometimes deformed the face. In Lamanai, once a major city of the Maya civilization, a pool of mercury was found under a marker in a Mesoamerican ballcourt. By 500 BC mercury was used to make amalgams (Medieval Latin amalgama, "alloy of mercury") with other metals.

Alchemists thought of mercury as the First Matter from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the transmutation of base (or impure) metals into gold, which was the goal of many alchemists.

Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word Ύδραργυρος (hydrargyros), which is a compound word meaning "water-silver" (hydr- = water, argyros = silver) — since it is liquid like water and shiny like silver. The element was named after the Roman god Mercury, known for speed and mobility. It is associated with the planet Mercury; the astrological symbol for the planet is also one of the alchemical symbols for the metal; the Indian word for alchemy is Rasavātam which means "the way of mercury". Mercury is the only metal for which the alchemical planetary name became the common name.

The mines in Almadén (Spain), Monte Amiata (Italy), and Idrija (now Slovenia) dominated the mercury production from the opening of the mine in Almadén 2500 years ago until new deposits were found at the end of the 19th century.

Toxicity and safety
Mercury and most of its compounds are extremely toxic and are generally handled with care; in cases of spills involving mercury (such as from certain thermometers or fluorescent light bulbs) specific cleaning procedures are used to avoid toxic exposure. Essentially, it is recommended to physically merge smaller droplets on hard surfaces, combining them into a single larger pool for easier removal by using an eyedropper, or by pushing it into a disposable container which must then be dealt with according to local regulations. Vacuum cleaners and brooms should not be used because they cause greater dispersal of the mercury. Afterwards, sulfur powder, zinc powder, or some other element that readily forms an amalgam (alloy) with mercury (e.g. finely-divided Cu or Bi) at ordinary temperatures is sprinkled over the area and subsequently collected and properly disposed of. Cleaning porous surfaces and clothing is not effective at removing all traces of mercury and it is therefore advised to discard these kinds of items should they be exposed to a mercury spill.

Mercury can be inhaled and absorbed through the skin and mucous membranes, so containers of mercury are securely sealed to avoid spills and evaporation. Heating of mercury, or compounds of mercury that may decompose when heated, is always carried out with adequate ventilation in order to avoid exposure to mercury vapor. The most toxic forms of mercury are its organic compounds, such as dimethylmercury and methylmercury. However, inorganic compounds, such as cinnabar are also highly toxic by ingestion or inhalation of the dust. Mercury can cause both chronic and acute poisoning.