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
Methanesulfonic acid Methanesulfonic acid Methanesulfonic acid (MsOH) is a colorless liquid with the chemical formula CHSOH. It is the simplest of the alkylsulfonic acids. Salts and esters of methanesulfonic acid are known as mesylates (or methanesulfonates, as in ethyl methanesulfonate). It is hygroscopic in its concentrated form. Methanesulfonic acid may be considered an intermediate compound between sulfuric acid (HSO), and methylsulfonylmethane ((CH)SO), effectively replacing an –OH group with a –CH group at each step. This pattern can extend no further in either direction without breaking down the –SO– group. Methanesulfonic acid can dissolve a wide range of metal salts, many of them