Mercury

Uses

Mercury’s unusual combination of being liquid, dense, and a good conductor of electricity made it useful in instruments for centuries — traditional thermometers and barometers relied on how precisely and visibly a column of mercury expands and contracts with temperature or pressure. Most of those uses have been phased out over the past few decades because of mercury’s toxicity, replaced by digital sensors or safer liquids. Mercury vapor is still used inside some fluorescent and compact fluorescent light bulbs, where it’s essential to producing the light, though these bulbs require careful disposal for the same reason.

Historically, mercury played a major role in gold and silver mining through a process called amalgamation, where it was used to extract precious metal from ore — a practice that caused serious environmental contamination in many regions and is now restricted or banned in much of the world. Dental amalgam fillings, another traditional use, have also declined sharply as alternative materials have become standard.

History

Mercury has been known since antiquity, with no single discoverer — it appears in the archaeological and written record of ancient Egypt, China, and Greece, sometimes found in tombs and sometimes used, ironically, in early medicines and cosmetics despite its toxicity. Its modern name comes from the fast-moving Roman god Mercury, a nod to how quickly liquid mercury moves and beads when disturbed, while its symbol, Hg, instead reflects its older Latin name, hydrargyrum. Understanding of just how dangerous mercury exposure could be developed gradually, and it was only in the 20th century that its use in everyday products came under serious scientific and regulatory scrutiny.