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
Caftaric acid little to no caftaric acid. Grape reaction product (2-S glutathionyl caftaric acid) is an oxidation compound produced from caftaric acid and found in wine. Malvidin 3-glucoside alone is not oxidized in the presence of grape polyphenol oxidase (PPO), whereas it is degraded in the presence of a crude grape PPO extract and of caftaric acid, forming anthocyanidin-caftaric acid adducts. Caftaric acid Caftaric acid is a non-flavanoid phenolic compound. It is found in the juice of grapes ("Vitis vinifera") and impacts the color of white wine. It is an esterified phenolic acid, composed of caffeic acid, a hydroxycinnamate produced by plants,