Royal water, or better known for its Latin name Aqua regia, is a fuming, corrosive liquid solution first invented by an Arab alchemist back in the 8th century.
It is a mixture of one part of nitric acid and three part of hydrochloric acid. The name comes from its yellow-orange hue and its ability to dissolve noble metals like gold and platinum, though not all metals.
These days, royal water is primarily used to produce chloroauric acid, the electrolyte used in the gold-refining chemical process.
During World War II, Hungarian chemist George de Hevesy famously dissolved two gold Nobel medals, which belong to German physicists Max von Laue and James Franck, in royal water to evade the confiscation by German Nazis.
Source: ACSReaction via Youtube