Mercury

Hg
Atomic No. - 80

Mercury is also called 'quicksilver.'

The History Says

Mercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500 BC. The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BC mercury was used to make amalgams with other metals.

The Present Scenario

Today, mercuric medicines and devices are generally considered hazardous. Neither are used to the extent they were in the past.

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Mercury is one of the five elements (caesium, francium, gallium and bromine) which are liquid at room temperature. It is officially classes as a mineral for historical reasons. It crystallizes at -40 degrees celsius forming hexagonal crystals.

Mercury is a rare element in the earth's crust. In nature it is usually found as small isolated drops which is associated with cinnabar, corderoite, livingstonite, and other minerals with cinnabar (HgS). Sometimes it is also found as large masses of fluid in rock cavities, mainly in active volcanic regions.

It is extracted by heating cinnabar in a current of air and condensing the vapor. Here follows the equation for the extraction:

                     HgS + O₂ = Hg + SO₂

Physical Properties of Mercury

Phase	Liquid
Density (near room temperature)	(liquid) 13.534 g/cm3
Melting point	234.32 K (-38.83°C, -37.89°F)
Boiling point	629.88 K (356.73°C, 674.11°F)
Heat of fusion	2.29 kJ/mol
Heat of vaporization	59.11 kJ/mol
Heat of capacity	(25°C) 27.983 J/(mol-K)

Atomic Properties of Mercury

Crystal structure	Rhombohedral
Oxidation states	2, 1 (mildly basic oxide)
Electronegativity	2.00 (Pauling scale)
Ionization energies	1st: 1007.1 kJ/mol 2nd: 1810 kJ/mol 3rd: 3300 kJ/mol
Atomic radius	150 pm
Atomic radius (calc.)	171 pm
Covalent radius	149 pm
Van der Waals radius	155 pm

Uses of Mercury

• For the manufacturing of industrial chemicals or for electrical and electronic applications.
• In thermometers.
• As mercury sphygmomanometers, a blood pressure meter.
• Thimerosal, an organic compound is used as preservative in vaccines and tattoo inks.
• As mercury barometers, diffusion pumps, coulometers, and many more laboratory instruments.
• In mercury arc rectifier, a type of electrical rectifier that converts alternate current into direct current.
• In mercury-vapor lamps and some neon advertising signs and fluorescent lamps.
• Once used as coolant for nuclear reactors, which has been replaced by sodium and also in the amalgamation process of refining gold and silver ores.
• As folk medicine and ceremonial purposes that involves ingestion, injection, or the sprinkling of elemental mercury around the home.
• In mercury switches, mercury cells and chlorine production, electrodes, batteries, and catalysts.
• As herbicides, insecticides, dental amalgams and liquid mirror telescopes.

Health and Mercury

Mercury poisoning is known as mercuralism. It is easily absorbed through the skin, respiratory and gastrointestinal tissues in humans. It attacks the central nervous system and endocrine system, adversely affecting the mouth, gums, and teeth. Highe exposure of mercury and over a longer period of time, it results in brain damage which can even lead to death.

Mercury also poses major health risk to the unborn fetus. Poisoned humans or animals often manifest excessive salivation. It is a condition known as mercurial ptyalism. The disease Minamata is also a form of mercury poisoning.

Precautions with Mercury

• The containers of mercury should be covered to avoid spillage and evaporation.
• Heating either mercury or its compounds should be done under a well-ventilated and filtered hood.
• Always wash hand after handling mercury.
• Never lick or ingest.
• Do not inhale vapors.

Occurrences of Mercury

• Almaden, Spain
• Idria, Slovenia
• Russia
• North America