Aqua regia

Aqua regia^[a]

Names
IUPAC name Nitric acid trihydrochloride
Other names Aqua regis Nitrohydrochloric acid Royal water
Identifiers
CAS Number	8007-56-5 Y
3D model (JSmol)	Interactive image
PubChem CID	90477010
UNII	X3TT5X989E Y
CompTox Dashboard (EPA)	DTXSID50893666
SMILES [N+](=O)(O)[O-].Cl.Cl.Cl
Properties
Chemical formula	HNO3 + 3 HCl
Appearance	Fuming liquid. Freshly prepared aqua regia is colorless, but it turns yellow, orange or red within seconds.
Density	1.01–1.21 g/cm3
Melting point	−42 °C (−44 °F; 231 K)
Boiling point	108 °C (226 °F; 381 K)
Solubility in water	Miscible
Vapor pressure	21 mbar
Hazards
NFPA 704 (fire diamond)	3 0 0 OX
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Aqua regia (/ˈreɪɡiə, ˈriːdʒiə/; from Latin, "regal water" or "royal water") is a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3.^[b] Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but it turns yellow, orange or red within seconds from the formation of nitrosyl chloride and nitrogen dioxide. It was named by alchemists because it can dissolve noble metals like gold and platinum, though not all metals.
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