What is Mercury?


Mercury at room temperature

nps staff photo

Symbol: Hg
Atomic Number: 80
Melting Point:
234 °K, 37 °F, -38 °C
Boiling Point:
629 °K, 674 °F, 356 °C



Mercury is the only metal that is liquid at standard conditions for temperature and pressure. It has one of the broadest ranges of its liquid state of any metal.

Mercury was often used in thermometers, barometers, and some electrical switches. Concern about the element's toxicity has led to many of these uses being phased out. Ironically mercury's use by the world has increased because of the "green movement." Mercury is used in the manufacture of energy efficient CFL bulbs. Disposal of these bulbs has caused some concerns about environmental dangers.

Mercury occurs in deposits throughout the world mostly as cinnabar. Cinnabar deposits were mined not far from the Klondike region allowing easy access to mercury which was used by the miners to extract fine gold. Thin mercury particles formed around fine gold. Using hydraulic type mining techniques, common during the Klondike Gold Rush, heavier gold particles would sink in the flowing water. Later the gold was recovered by burning off the mercury.



Mercury has been found in both ancient Egyptian and Chinese cultures that date from 1500 BC. Its use was thought to prolong life, heal fractures, and maintain generally good health. The ancient Greeks, Romans and Egyptians were known to use mercury in cosmetics which sometimes led to disfigurement.

Many early alchemists viewed mercury as the First Matter from which all other metals were formed. They believed different metals, including gold, could be produced by varying the quantity and quality of sulfur and mercury.

From the mid-18th to the mid-19th centuries, a mercury compound, mercuric nitrate, was used in the making of felt hats. This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. The psychological symptoms associated with mercury poisoning are said by some to have inspired the phrase "mad as a hatter."


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