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 extraction of an acid to a mixture of an organic base and acid will result in the acid remaining uncharged, while the base will be protonated to form a salt. If the organic acid, such as a carboxylic acid, is sufficiently strong, its self-ionization can be suppressed by the added acid. Conversely, the addition of a base to a mixture of an organic acid and base will result in the base remaining uncharged, while the acid is deprotonated to give the corresponding salt. Once again, the self-ionization of a strong base is suppressed by the added base. The acid-base extraction procedure