The Chemical Properties of Gold
One of the best known chemical properties of gold is its non-reactivity; a major factor in its continuous usage past and present. Another useful chemical property is its resistance to mineral acids. It can only be dissolved by extremely oxidising acids such as aqua regia or selenic acid.
Dissolving gold in aqua regia results in chloroauric acid (HAuCl4), which is important in the production of gold alloys. The chemical representation of this process is as follows.
2 Au + 9HCl + 5 HNO3 → 2 HAuCl4 + 4 NO2 + 6 H2O + NOCl