Aquaregia is a mixture of the following in the ratio 1 : 3 by volume– (1) cone. HNO3 and cone. HCL (2) conc. HNO3 and conc. H2SO4 (3) dil. HCl and dil. HNO3 (4) cone. HCl and cone. HNO3
(3) dil. HCl and dil. HNO3 Explanation: Aqua regia or nitro-hydrochloric acid is a highly corrosive mixture of acids which is formed by freshly mixing concentrated Nitric acid (HNO3) and Hydrochloric acid (HCl), optimally in a volume ratio of 1:3. It is used in dissolving gold.