Mercury — named after a Roman god known for speed and agility — is a chemical element that has fascinated humans for thousands of years. Mercury is the only metallic element that is liquid under standard conditions. It flows easily and has very high surface tension, so it forms shiny rounded beads.
Its atomic number is 80, which means that a mercury atom has 80 protons in its nucleus. Mercury is rarely found in its elemental form. It is most often found in cinnabar, a form of mercury sulfide. Mercury is one of the seven metals of antiquity — metals that humans identified and used in ancient times. The other metals of antiquity are gold , silver, copper, iron, tin and lead. The alchemists thought that mercury was very special — the matter from which all metals were formed.
It represented solid and liquid, heaven and Earth, and life and death. It is the only metal of antiquity that is still referred to by its planetary name. Humans had uses for mercury long before the alchemists tried to use it to turn base metals into gold. Egyptian tombs dating from BC held vials of liquid mercury. Its use in China and India dates before BC. Mercury and other precious items were found in the depths of an year-old pyramid in Mexico. The metal is condensed and washed with nitric acid to purify it, and then distilled.
Mercury can form alloys with gold, silver, zinc and cadmium, which are called amalgams. Through those amalgams, mercury can be used to extract gold from rocks. When mercury comes into contact with gold, the gold dissolves into the mercury and then the two are separated, with the mercury being distilled off.
Mercury also forms compounds with other elements. Interestingly, one of such compounds — mercury nitrate — played a role in the coining of the term "mad as a hatter. In the 18th century people used the mercury nitrate compound to clean the pelts before they turned them into hats.
Other common mercury compounds include mercuric chloride HgCl 2 — a highly poisonous salt and that was once used as a wound disinfectant. Another example is mercurous chloride Hg 2 Cl 2 , also known as calomel — an antiseptic used to kill bacteria, according to the Jefferson Lab. Mercuric sulfide HgS is used to make a red paint pigment called vermilion, and mercuric oxide HgO is used to make mercury batteries. Due to mercury's toxic potential, researchers keep stumbling upon ways in which the element may be harmful to humans and the environment.
For example, scientists have argued about the potential toxicity of amalgam used in dental fillings that contains about 50 percent mercury. In a review of literature published in in the journal Gesundheitswesen, researchers found that exposure to mercury in dental fillings could lead to kidney and autoimmunity problems, neurobehavioral changes and even autism.
What's in a name? Named after the planet Mercury. Mercury's chemical symbol comes from the Greek word hydrargyrum , which means "liquid silver. Say what? Mercury is pronounced as MER-kyoo-ree. Mercury was known to the ancient Chinese and Hindus and has been found in year old Egyptian tombs. Mercury is not usually found free in nature and is primarily obtained from the mineral cinnabar HgS. Spain and Italy produce about half of the world's supply of Mercury. Mercury can be used to make thermometers, barometers and other scientific instruments.
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