what is aqua regia

Aqua regia is a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3. It is a fuming liquid that turns yellow, orange, or red within seconds from the formation of nitrosyl chloride and nitrogen dioxide. Aqua regia was named by alchemists because it can dissolve the noble metals gold and platinum, though not all metals. Upon mixing of concentrated hydrochloric acid and concentrated nitric acid, chemical reactions occur, resulting in the volatile products nitrosyl chloride and chlorine gas. Aqua regia is frequently used to dissolve gold and platinum, and it is also used in etching and in specific analytic procedures. It is also used in some laboratories to clean glassware of organic compounds and metal particles. Aqua regia is a powerful tool for chemical research that has been used for centuries, but it is also a dangerous liquid that requires appropriate precautions when handling.