Aqua regia is a highly corrosive and powerful mixture of concentrated nitric acid (HNO3) and concentrated hydrochloric acid (HCl). The term "aqua regia" is Latin for "royal water." The mixture is called so because it was historically known for its ability to dissolve noble metals, including gold and platinum, which were considered "royal" metals.
Aqua regia is primarily used in chemical laboratories for various purposes, including:
Metal dissolution: Aqua regia's main function is to dissolve noble metals like gold, platinum, and palladium, which are otherwise resistant to most acids. The mixture's ability to dissolve these metals is due to the presence of nitric acid, which acts as an oxidizing agent, and hydrochloric acid, which provides chloride ions that form soluble complexes with the metal ions.
Material analysis: Aqua regia is used for the preparation of samples in analytical chemistry, particularly for the determination of metal content. By dissolving a solid material in aqua regia, the resulting solution can be analyzed to determine the concentration of specific metals present.
Cleaning glassware: Due to its corrosive nature, aqua regia is used for cleaning and removing stubborn deposits from laboratory glassware. It can dissolve organic compounds, mineral residues, and other impurities, making it effective for cleaning purposes.
It is important to note that aqua regia is highly reactive and hazardous. It releases toxic gases, such as nitrogen dioxide (NO2), and should only be handled by experienced individuals in a well-ventilated fume hood. Proper safety precautions, including the use of protective equipment and adherence to appropriate handling procedures, are crucial when working with aqua regia.