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,
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