Aqua Regis, or REGIA (literally 'royal water'), is the common name applied to a mixture of 1 part of nitric acid, and 2, 3, or 4 parts of hydrochloric acid. The general proportion is 1 to 2. The term aqua regia was given to the mixture from the power it possesses of dissolving gold, which is the king of the metals.
Aqua Regis
Chambers's Encyclopaedia, Volume 1: A to Beaufort, p. 355
Source scan(s): p. 0374