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Why did mercury thermometers and barometers use mercury?
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zinc group element
Modern version of the periodic table of the elements (printable).
Mercury was historically used in thermometers and barometers due to its unique physical properties as a chemical element in the zinc group.
Why Mercury Was Used
- Thermometers: Mercury is the only elemental metal that is liquid at room temperature. It does not wet or cling to glass, and it exhibits rapid, uniform volume expansion throughout its liquid range, which made it highly effective for measuring temperature changes.1
- Barometers: Mercury’s high density—approximately 13.5 times that of water—allowed for the construction of compact, manageable instruments. For example, a mercury barometer requires a tube only about 1.2 meters (4 feet) long to measure atmospheric pressure, whereas a water-based barometer would require a tube roughly 10 meters (33 feet) long. Additionally, its low vapour pressure made it ideal for these applications.21
Due to the significant health risks associated with mercury poisoning, the use of mercury in these instruments has been largely phased out in favor of safer, modern alternatives like electronic digital thermometers and aneroid barometers.21