- •Copper subgroup physical properties
- •Copper subgroup trends
- •Preparation
- •Electronic Configurations & Oxidation States
- •Chemical Properties Free elements
- •Compounds Cu(I).
- •Compounds of Ag
- •Mendeleev's predicted elements
- •The Pourbaix diagram for copper in pure water, acid or alkali conditions. Note that copper in neutral water is more noble than hydrogen.
- •Aqua regia or aqua regis
- •Dissolving gold
- •Similar equations can be written for platinum. As with gold, the oxidation reaction can be written with either nitric oxide or nitrogen dioxide as the nitrogen oxide product.
- •Decomposition of aqua regia
- •History
- •Cuprates. High Temperature Superconductors (hts)
- •History
- •Synthesis
- •Laboratory Preparation
- •Leaching
- •Gold smelting Mercury removal
Gold smelting Mercury removal
Mercury is a health hazard, especially when in gas form. To remove this hazard, before smelting, gold precipitates from electrowinning or Merrill-Crowe processes are usually heated in a retort to recover any mercury present, that would otherwise cause health and environmental problems due to its release (volatilization) during smelting. The mercury present is not usually from the mercury amalgamation process that is no longer used by formal gold mining companies, but from mercury in the ore that has followed gold through the leaching and precipitation processes.
In the event that there are high levels of copper or silver present, leaching of the precipitate using nitric or sulfuric acids may be required.
Gravity concentration has been historically the most important way of extracting the native metal using pans or washing tables. However, froth flotation processes may also be used to concentrate the gold. In some cases, particularly when the gold is present in the ore as discrete coarse particles, a gravity concentrate can be directly smelted to form gold bars. In other cases, particularly when the gold is present in the ore as fine particles or is not sufficiently liberated from the host rock, the concentrates are treated with cyanide salts, a process known as cyanidation leaching, followed by recovery from the leach solution. Recovery from solution typically involves adsorption on activated carbon followed by solution concentration or stripping and or electrowinning.
Sometimes gold is present as a minor constituent in a base metal (e.g. copper) concentrate, and is recovered as a by-product during production of the base metal. For example, it can be recovered in the anode slime during the electrorefining process.