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
Metal Gear Acid vecuronium bromide, the chemical used by Elsie and Frances to hijack Flight 326. The third is stated to be an acronym for Active Command Intelligence Duel, a reference to the game's mixture of turn-based tactics with card-based gameplay. The game's soundtrack was composed by Nobuko Toda, Shuichi Kobori and Akihiro Honda. The soundtrack was released on December 21, 2005, packaged with the "Metal Gear Acid 2" soundtrack. The album's title is "Metal Gear Acid 1 and 2 Original Soundtrack". "Metal Gear Acid" received generally positive reviews from critics. "Acid" was followed by a sequel for the PSP, "Metal Gear Acid