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 the Brønsted-Lowry model, the solvent does not necessarily have to be water that is required by the Arrhenius Acid-Base model. For example, consider what happens when acetic acid, CHCOOH, dissolves in liquid ammonia. An H ion is removed from acetic acid, forming its conjugate base, the acetate ion, CHCOO. The addition of an H ion to an ammonia molecule of the solvent creates its conjugate acid, the ammonium ion, . The Brønsted–Lowry model calls hydrogen-containing substances (like HCl) acids. Thus, some substances, which many chemists considered to be acids, such as SO or BCl, are excluded from this classification due