mercur

Mercur, also sometimes spelled mercur in historical or regional usage, refers to the chemical element mercury (Hg), atomic number 80. Mercury is the only metal that is liquid at standard room temperature, appearing as a dense, silvery liquid with a high surface tension. It occurs naturally in the Earth’s crust, predominantly in the mineral cinnabar (mercury sulfide). Commercial mercury is produced by roasting cinnabar ore to release mercury vapor, which is then condensed into liquid metal.

Physical and chemical properties: Mercury has a density of about 13.5 g/cm3 at 20°C, a melting point of −38.83°C, and a boiling point of 356.73°C. It forms amalgams with many metals and can exist in elemental form or in various oxidation states, including mercurous (Hg2^2+) and mercuric (Hg2+) compounds. In the environment, certain bacteria convert inorganic mercury to methylmercury, a highly toxic organic form that bioaccumulates in the food chain.

Uses and history: Mercury has been used in thermometers, barometers, and electrical switches; dental amalgams contain mercury alloy. It played a historical role in gold extraction and various scientific instruments. Because of its toxicity, many traditional applications have been reduced or strictly regulated.

Name and etymology: The element is named after the Roman god Mercury; its chemical symbol Hg derives from hydrargyrum, from Greek hydr- meaning “water” and argyros meaning “silver.”