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Nitric acid is a powerful oxidizer, which will dissolve a very small quantity of gold, forming gold(III) ions (Au 3+). The hydrochloric acid provides a ready supply of chloride ions (Cl −), which react with the gold ions to produce tetrachloroaurate(III) anions ([AuCl 4] −), also in solution. The reaction with hydrochloric acid is an ...
It is an electrolytic process using pure gold for the cathode (or titanium as a starter cathode) and chloroauric acid (gold chloride-hydrochloric acid) as the electrolyte; this is made by dissolving gold with chlorine gas in the presence of hydrochloric acid. Gold is dissolved at the anode, and pure gold, traveling through the acid by ion ...
Gold is unaffected by most acids. It does not react with hydrofluoric, hydrochloric, hydrobromic, hydriodic, sulfuric, or nitric acid. It does react with selenic acid, and is dissolved by aqua regia, a 1:3 mixture of nitric acid and hydrochloric acid. Nitric acid oxidizes the metal to +3 ions, but only in minute amounts, typically undetectable ...
Akin to its use for pickling, hydrochloric acid is used to dissolve many metals, metal oxides and metal carbonates. The conversions are often depicted in simplified equations: Zn + 2 HCl → ZnCl 2 + H 2 NiO + 2 HCl → NiCl 2 + H 2 O CaCO 3 + 2 HCl → CaCl 2 + CO 2 + H 2 O. These processes are used to produce metal chlorides for analysis or ...
Chloroauric acid is the product formed when gold dissolves in aqua regia. [15] On contact with water, AuCl 3 forms acidic hydrates and the conjugate base [AuCl 3 (OH)] −. A Fe 2+ ion may reduce it, causing elemental gold to be precipitated from the solution. [1] [16] Other chloride sources, such as KCl, also convert AuCl 3 into [AuCl 4] −.
Engineers mix the gold-cyanide solution with carbon, which bonds with the gold particles. An acidic solution — generally hydrochloric acid — is used to separate the gold from the carbon. The gold-laden liquid is poured over electrified steel, which attracts flakes of the metal. Heavy metals are a byproduct of refinement.
Ruthenium can be dissolved in aqua regia, a highly concentrated mixture of hydrochloric acid and nitric acid, only when in the presence of oxygen, while rhodium must be in a fine pulverized form. Palladium and silver are soluble in nitric acid, while silver's solubility in aqua regia is limited by the formation of silver chloride precipitate. [8]
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