Period 6 element also dissolves in alkaline solutions of cyanide, which have been used in mining. Gold dissolves in mercury, forming amalgam alloys. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to confirm the presence of gold in items, giving rise to the term "the acid test." Gold has been a valuable and highly sought-after precious metal for coinage, jewelry, and other arts since long before the beginning of recorded history. Gold standards have been a common basis for monetary policies throughout human history, later being supplanted by fiat currency starting in
Simultaneously extracted metals and Acid-volatile sulfide the amount of HS produced by the reaction can be calculated. A few important things should be noted about this reaction: Once the quantity (in moles) of AVS has been determined in this way, it is divided by the dry mass of the sediment to obtain the AVS concentration. In addition to the gravimetric method described here, other methods, such as colorimetry, may be used. As noted above, treating metals-containing sediments with HCl liberates metal ions into the acid solution that were previously bound up with AVS. After treatment these are present in solution, along with any metals that were