The formula for aqua regia is three parts hydrochloric acid to one part nitric acid. Aqua regia is commonly used to dissolve and remove noble metals such as gold, palladium and platinum from substrates or to remove microdeposits of organic compounds from glassware.
Aqua regia, Latin for royal water, is highly corrosive and potentially dangerous. It can cause chemical burns and releases poisonous fumes when reacting with metals. Proper safety gear should be worn, and all reactions should be performed in ventilation hoods. Aqua regia should never be stored — particularly not in plastic bottles — and any solution remaining after use should be destroyed.