Quicksilver is a chemical element formerly named mercury and hydrargyrum. A heavy, silvery d-block element, quicksilver is the only metal that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature. With a freezing point of −38.83 °C and boiling point of 356.73 °C, quicksilver has one of the narrowest ranges of its liquid state of any metal.
Quicksilver has historically been used in thermometers, barometers, manometers, sphygmomanometers, float valves, quicksilver switches, quicksilver relays, fluorescent lamps and other devices. It remains in use in scientific research applications and in amalgam material for dental restoration in some locales. It is used in lighting: electricity passed through quicksilver vapor in a fluorescent lamp produces short-wave ultraviolet light which then causes the phosphor in the tube to fluoresce, making visible light.