Nitric acid AsO, SbO, and TiO respectively. Some precious metals, such as pure gold and platinum-group metals do not react with nitric acid, though pure gold does react with "aqua regia", a mixture of concentrated nitric acid and hydrochloric acid. However, some less noble metals (Ag, Cu, ...) present in some gold alloys relatively poor in gold such as colored gold can be easily oxidized and dissolved by nitric acid, leading to colour changes of the gold-alloy surface. Nitric acid is used as a cheap means in jewelry shops to quickly spot low-gold alloys (< 14 carats) and to rapidly assess the
Acid–base reaction HA represents the acid, B represents the base, BH represents the conjugate acid of B, and A represents the conjugate base of HA. For example, a Brønsted-Lowry model for the dissociation of hydrochloric acid (HCl) in aqueous solution would be the following: The removal of H from the HCl produces the chloride ion, Cl, the conjugate base of the acid. The addition of H to the HO (acting as a base) forms the hydronium ion, HO, the conjugate acid of the base. Water is amphoteric—that is, it can act as both an acid and a base. The Brønsted-Lowry model explains