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just I want to know what kind of acid spoil golden becaus golden is precious metal.

One Response to “What kind of acid spoil golden?”

1. Maverick on May 6th, 2009 6:36 pm

   Gold is attacked by and dissolves in alkaline solutions of potassium or sodium cyanide, and gold cyanide is the electrolyte used in commercial electroplating of gold onto base metals and electroforming.

   Gold chloride (chloroauric acid) solutions are used to make colloidal gold by reduction with citrate or ascorbate ions.

   Gold chloride and gold oxide are used to make highly-valued cranberry or red-colored glass, which, like colloidal gold sols, contains evenly-sized spherical gold nanoparticles.

   Aqua regia (Latin for royal water) is a highly corrosive, fuming yellow or red solution.

   The mixture is formed by freshly mixing concentrated nitric acid and concentrated hydrochloric acid, usually in a volumetric ratio of one to three respectively.

   It is one of the few reagents that dissolves gold and platinum. It was so named because it can dissolve the so-called royal, or noble metals, although tantalum, iridium, and a few other metals are able to withstand it.

   Aqua regia dissolves gold, even though neither constituent acid will do so alone, because, in combination, each acid performs a different task.

   Nitric acid is a powerful oxidizer, which will actually dissolve a virtually undetectable amount of gold, forming gold ions (Au3+).

   The hydrochloric acid provides a ready supply of chloride ions (Cl-), which react with the gold to produce chloraurate anions, also in solution.

   The reaction with hydrochloric acid is an equilibrium reaction which favors formation of chloraurate anions (AuCl4-).

   This results in a removal of gold ions from solution and allows further oxidation of gold to take place, and so the gold is dissolved.

   In addition, gold may be oxidized by the free chlorine present in aqua regia.

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