Gold: not so 'noble' after all
Gold is not as resistant to chemical reactions as once thought, according to a team of researchers from Germany, France and Sweden. The team reached its conclusion after having tested the metal at very high pressure at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Gold has been known and highly valued since prehistoric times. The unique role that the metal plays in the world is related in part to the fact that it is the most unreactive (noble) of all metals. Although gold can form bonds with other chemicals, it has outstanding resistance to oxidation, even at high temperatures. Because of its ability to withstand high pressures and temperatures, as well as its high isothermal compressibility, gold has been widely used as a pressure marker for experiments with pressure levels above 100 GPa (1 million atmospheres). However, the researchers have now discovered that gold reacts when it is subjected to pressures above 240GPa (two million four hundred atmospheres). They made the discovery by placing a sample of gold inside a diamond anvil cell, which was then electrically heated externally. This allowed the researchers to study the gold at pressures similar to those found at the Earth's core. 'These new experimental and theoretical results remind us that there is no 'absolute' unchangeable material, and the noblest of all metals, gold, is not an exception from this rule,' explains Leonid Dubrovinsky, the main researcher in the experiment. The researchers believe that their discovery will contribute to setting standards for high-pressure experiments.