Gold element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term "acid test". Gold also dissolves in alkaline solutions of cyanide,
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