What Is Mercury (Hg) Used for?


If your thermometer contains mercury, the Environmental Protection Agency wants you to replace it with one that doesn't. Also known by its chemical symbol, Hg, this intriguing metal, which liquefies at room temperature, has uses ranging from crop treatment to dental care. It's also a dangerous substance that can lead to health problems and even death. Three types of mercury exist: elemental, inorganic compounds and organic compounds.

Mercury that Flows

  • Elemental mercury, which also goes by the name of quicksilver, is a liquid that has a silver-white color. Heat it to 356.73 °C, and the liquid turns into a harmful gas that has no odor or color. However, when elemental mercury is enclosed inside a thermometer, it is safe-- unless the thermometer breaks, releasing the mercury. Since glass thermometers are bound to break, it's not a good idea to put them in your child's mouth to measure for fever-- use an alcohol-based thermometer instead. Thermometers containing elemental mercury find their way into laboratories, medical institutions and industries, and the home. Dental amalgams, consisting of about 50 percent mercury, along with tin, copper and silver, are still used but are being increasingly replaced by resin or porcelain filling due to concerns about toxicity.

Inorganic and Organic Mercury

  • Inorganic mercury, used frequently in chemistry experiments, is the least harmful kind of mercury. Found in useful compounds such as mercuric sulphide and mercuric nitrate, inorganic mercury is white with the exception of cinnabar, which is red. Mercuric chloride, another mercury compound, still exists in some pesticides and disinfectants, but most pharmaceutical and agricultural uses of inorganic mercury in the U.S. are discontinued. School laboratories also use inorganic mercury. Organic mercury, or methylmercury, is usually found in the environment. In the past, industrially produced methyl mercury that was released into the environment led to serious intoxication of animals and people. One of the most famous examples of "pollution diseases" is Minimata disease, the neurological syndrome that results from methyl mercury poisoning. It got its name from the severe poisoning of thousands of people from industrial release of methyl mercury into Minimata Bay in Japan. Today, it mainly forms when microorganisms cause mercury and carbon compounds to combine.

Mercury in Other Products

  • Mercury's ability to function as an electrical conductor makes it suitable for use in many devices, such as thermostats, flame sensors and switches. Some clothing irons have automatic cut-off switches that contain mercury. Mercury also provides light in the form of fluorescent lamps that contain vapor and metallic mercury. Although the U.S. has phased out the use of mercury in batteries, you'll still find it in small button batteries used in small devices.

Mercury: Its Dangers

  • A neurotoxin, elemental mercury poisoning causes symptoms such as difficulty breathing, cough, and swollen, bleeding gums. Inorganic mercury damages the nervous system and kidneys; a large overdose can lead to severe diarrhea, kidney damage, and death. Organic mercury can cause severe central nervous system damage and birth defects. People usually ingest this type of mercury by eating contaminated fish. Death can occur with extreme exposure to methylmercury. The FDA warns consumers not to use cosmetics that contain mercury. Although these products are illegal, they arrive in the U.S. from abroad as anti-aging treatments, acne treatments and similar products that treat the skin. U.S. travelers may also bring them home after purchasing them in other countries.


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