Group 12 element is a common reducing agent in organic synthesis, and is also used in high-pressure sodium lamps. Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. Since the amalgam reacts with air to give aluminium oxide, small amounts of mercury corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft. Most of the chemistry has been observed only for the first three members of the group 12. The chemistry of copernicium
Amalgam tattoo from pencil leads), and is sometimes termed a "graphite tattoo", although this is less common than tattooing with amalgam. The diagnosis is clinical. Amalgam tattoo can be distinguished from other causes of localized oral pigmentation because it does not change significantly in size or color, although it may appear to slowly enlarge for several months after the initial implantation of the metal particles. Some amalgam tattoos appear radio-opaque on radiographs (i.e. they show up on x-rays), although in many cases amalgam tattoos have no radiographic features since the responsible particle(s) of amalgam are very small even though clinically the area