Introduction
Gold (Au) and uranium (U) are two of the most valuable and important metals mined by humankind. They have some similar and some contrasting properties, but their uses are very different. Gold has been used for millennia for its intrinsic value in coins and jewelry, but more recently it has been used for other purposes, especially medical and sensor applications. Uranium usage, on the other hand, has developed only in the mid twentieth century for energy and weapons production.
Gold is a member of Group 11 of the transition metals. It is a malleable, ductile, soft metal that can be beaten into a very fine sheet or extruded into a thin wire. It has one of the highest electrode potentials for a metal (E 0 ΒΌ ΓΎ1.691 V), which means that it does not readily corrode. These, and other properties summarized in Table 23.1, give gold certain characteristics that have made it one of the most sought-after metals for thousands of years. Because of its colour and scarcity, along with its malleability, ductility and stability, gold has long been used for coinage and jewelry. The same properties have also made gold and its alloys a commonly used material in restorative and conservative dentistry and orthodontics [1]. Gold has a long history of medical use, and in the twentieth century compounds of gold were developed for treatment of rheumatoid arthritis and cancer [2]. A property of gold that has received considerable interest recently is its ability to form nanoparticles, typically of diameter <50 nm, which has led to the use of gold as a catalyst, for
Trace Elements in Soils