Mercury is extracted from cinnabar by roasting it in air, followed by condensation of the mercury vapour.
Most of the methods of extraction of mercury rely on the volatility of the metal and the fact that cinnabar is readily decomposed by air or by lime to yield the free metal. Over 90 percent of the world’s supply of mercury comes from China it is often a by-product of gold mining.Ĭinnabar is mined in shaft or open-pit operations and refined by flotation. Extremely rare natural alloys of mercury have also been found: moschellandsbergite (with silver), potarite (with palladium), and gold amalgam.
Native mercury occurs in isolated drops and occasionally in larger fluid masses, usually with cinnabar, near volcanoes or hot springs. The principal ore is the red sulfide, cinnabar. Mercury occurs in Earth’s crust on the average of about 0.08 gram (0.003 ounce) per ton of rock. In the early 21st century, however, mercury-cell plants for manufacturing chlorine and sodium hydroxide have mostly been phased out. In the 20th century the use of mercury in the manufacture of chlorine and sodium hydroxide by electrolysis of brine depended upon the fact that mercury employed as the negative pole, or cathode, dissolves the sodium liberated to form a liquid amalgam. Some mercury is used in the preparation of pharmaceuticals and agricultural and industrial fungicides. An electrical discharge through mercury vapour contained in a fused silica tube or bulb produces a bluish glow rich in ultraviolet light, a phenomenon exploited in ultraviolet, fluorescent, and high-pressure mercury-vapour lamps. The good electrical conductivity of mercury makes it exceptionally useful in sealed electrical switches and relays. Gold and silver dissolve readily in mercury, and in the past this property was used in the extraction of these metals from their ores. However, mercury’s toxicity has led to its replacement in these instruments. (Mercury thermometers were supplanted by more accurate electronic digital thermometers in the early 21st century.) Barometers and manometers also used its high density and low vapour pressure. Mercury does not wet glass or cling to it, and this property, coupled with its rapid and uniform volume expansion throughout its liquid range, made it useful in thermometers. An amalgam with silver is used as a filling in dentistry. It alloys with copper, tin, and zinc to form amalgams, or liquid alloys.
Liquid mercury beads and a glass container.
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