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Mercury is sensitive to subtle pressure changes, so it was used in barometers and altimeters. The changes in air pressure that come with changes in weather or elevation are detectable by watching the way mercury behaves in a tube under vacuum. Evangelista Torricelli (1608 - 1647) invented the mercury barometer around 1644.
The largest manufacturer of mercury barometers in the United States stopped producing them in January 2007. Aneroid barometers and water-based barometers need no mercury.
Antique barometers often contain mercury. Old aneroid barometers have complex works that look like that of a clock. If it seems possible to gently remove the cover, look for a glass ampoule or vial part-full full of shiny liquid. Use great caution.
The greatest dangers involved with the use of mercury in barometers may be from breakage or fire. Broken barometers can cause dangerous and costly cleanups. House fires vaporize mercury, introducing it to the atmosphere. It is unknown how much atmospheric mercury is introduced this way, but heat vaporizes metallic mercury thoroughly. The mercury released this way is deposited on land and water where it can become methylmercury and enter the food chain. More information on this process is available in the section on Mercury and Its Compounds.
Washingtonians who find mercury-containing barometers in their homes should call 1-800-recycle for the location of local hazardous-waste collection sites or events. While barometers have been useful tools, we now have better, safer ways to tell the weather.
Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html.
