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
Acid–base imbalance Any combination is possible, as metabolic acidosis and alkalosis can co exist together. The traditional approach to the study of acid–base physiology has been the empirical approach. The main variants are the base excess approach and the bicarbonate approach. The quantitative approach introduced by Peter A Stewart in 1978 is newer. There are numerous reasons that each of the four processes can occur (detailed in each article). Generally speaking, sources of acid gain include: Sources of acid loss include: The body's acid–base balance is tightly regulated. Several buffering agents exist which reversibly bind hydrogen ions and impede any change in