AuCN2

AuCN2 is a chemical species that can be formed in aqueous solutions containing gold(I) cyanide complexes. When gold(I) is present in the presence of excess cyanide ions, it readily forms stable dicyanoaurate(I) complexes. The most common form is the linear [Au(CN)2]- anion. This complex is highly soluble in water and is a key species in gold cyanidation processes, which are widely used for the extraction of gold from ores.

The formation of the dicyanoaurate(I) complex is a result of gold's strong affinity for cyanide. The reaction can be represented as Au+ + 2CN- <=> [Au(CN)2]-. The stability of this complex is very high, with a large formation constant. This stability explains why cyanide is such an effective leaching agent for gold. Even very low concentrations of gold in solution can be effectively stabilized by cyanide.

In industrial gold processing, the gold ore is typically treated with an aqueous solution of sodium cyanide or potassium cyanide in the presence of oxygen. The oxygen oxidizes the gold metal to gold(I), which then immediately forms the [Au(CN)2]- complex. This dissolved complex is then separated from the solid ore. Later, the gold can be recovered from the solution through processes like precipitation with zinc (Merrill-Crowe process) or adsorption onto activated carbon (carbon-in-pulp or carbon-in-leach). The stability of AuCN2 is crucial for efficient gold recovery.