Dissolution of gold

The overall reaction for the dissolution of gold in dilute aerated, aqueous alkaline cyanide solution may be expressed by the classical Eisner equation ... 

The dissolution of gold in its native form by cyanidation involves oxidation to Au1,... 

It is believed that copper acts as the oxidant in these systems, effecting the dissolution of gold as an ammine complex,... 

Groenewald, T. The dissolution of gold in acidic solutions of thiourea. Hydrometallurgy 1976, I, 277-290. 

Conway and coworkers [372] have studied anodic dissolution of gold coupled with anodic oxide formation in HCIO4 solutions with addition of bromide ions. It was observed that gold initially dissolves in a 3e oxidation process. 

Dissolution of gold and silver from Au/Ag alloys in aerated cyanide solutions has been investigated using rotating disc electrodes [551]. Dissolution was partially controlled by transport of either oxygen or cyanide. Kinetics of anodic dissolution of gold in cyanide solutions containing different metal ions has been extensively... 

Dissolution of Gold Foil. Put a small piece (about 0.01 g) of gold foil into a small porcelain bowl, treat it with 3-5 drops of aqua regia, and evaporate on a water bath. What forms Leave a part of the product dry, dissolve the remainder in the smallest possible amount of water, and use the solution for the following experiments. 

In the dissolution of gold (or silver) by cyanidation, the milled ore is agitated with dilute alkaline cyanide solution, and the air is introduced (equation 1). 

BATH. — Symbol 1. Of the dissolution of gold and silver 2. Of the purification of these metals. 

Process of cyanide dissolution of gold (gold is not soluble in hot acids) Dissolution of gold in dilute cyanide solutions recognized as electrochemical process... 

This equation is somewhat simplified in fact there are more products formed during the process. Nitrosyl chloride, NOC1, is one of the products which can easily be identified. The oxidative action of chlorine is based on the process described in the previous section. The dissolution of gold can be expressed with the equation ... 

Gold metal will not dissolve in either concentrated nitric acid or concentrated hydrochloric acid. It will dissolve, however, in aqua regia, a mixture of the two concentrated acids. The products of the reaction are the AuC14 ion and gaseous NO. Write a balanced equation for the dissolution of gold in aqua regia. 

The mechanism of the dissolution of gold and silver by cyanide remained in dispute until 1966 when Habashi (H2) presented conclusive evidence that the overall chemical reaction representing the dissolution of gold in cyanide is... 

The presence of copper, even in concentration below 0.10% affects not only the dissolution of gold but also the precipitation of pure gold from the solution by zinc. The copper minerals increase cyanide consumption by going into solution and forming the copper cyanogen complex. Zinc in the ore reacts in the same way as copper. 

Corrosion potentials of hematite, magnetite, maghemite, and roasted gold ore indicated that they can act as a cathode and could potentially or at least temporarily promote the dissolution of gold in galvanic coupling. 

Filmer, A.O. (1982). The dissolution of gold from roasted pyrite concentrates. Journal of the South African Institute of Mining and Metallurgy, 90-94. 

Kirk, D.W. Foulkes, F.R. (1980). Anodic dissolution of gold in aqueous alkaline cyanide solutions at low overpotentials. Journal of the Electrochemical Society, 127(9), 1993-1997. doi 10.1149/1.2130051... 

Chandra, I., Jeffrey, M. I. (2004).An electrochemical study of the effect of additives and electrolyte on the dissolution of gold in thiosulfate solutions. Hydrometallurgy,73(3-4), 305-312. 

Zhang, S., Nicol, M. J. (2003). An electrochemical study of the dissolution of gold in thiosulfate solutions Part I Alkaline solutions. Journal of Applied Electrochemistry, 33(9), 767-775. doi 10.1023/A 1025502303122... 

Most of the reported assays have been based on chemical dissolution of gold nanoparticle tag (in a hydrobromic acid/bro-mine mixture) followed by accumulation and stripping analysis of the resulting Au3+ solution. Due to the toxicity of the HBr/ Br2 solution, direct solid-state detection of silver precipitate on gold nanoparticle-DNA conjugates was reported by Wang et al. 

Hydrometallurgy makes use of redox and complexation reactions for the recovery of valuable metals from ores. This is exemplified by the dissolution of gold metal in ores through oxidation by air and complexation by cyanide. 

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