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 perfusion test Acid perfusion test Acid perfusion test, also called the Bernstein test, is a test done to reproduce the pain when the lower esophagus is irrigated with an acid solution in people with GERD (gastroesophageal reflux disease). There will be a negative result in normal people, but a false positive reading may be seen in up to 15% of people. Bernstein test is obsolete nowadays. 24 hour pH monitoring is the gold standard for GERD. However, the initial management is with proton pump inhibitors. If the patient does not respond to it, and continues to have symptoms of GERD, i.e. heartburn,