I'm not convinced the problems are equivalent. Iron ore grades are ~60% where as 2ozs of gold grades at ~0.006% in percentage terms (find me the concentrate grades from Nevada). But even if you are right how much copper is required per oz and is it reusable or does it need some form of purification before reuse?
You also didn't respond to my other question about nitric acid.
This from a previous BBX (14/3) update.
"Each bar was divided into four equal parts, one of which was dissolved in nitric acid and metals precipitated from the solution. The resultant precipitate was fused to form metallic buttons which were analysed by fire assay using a gravimetric finish"
From what I've read about dissolving gold it can't be done with nitric acid alone. How do you address this?
https://en.wikipedia.org/wiki/Aqua_regia
Dissolving gold[edit]
Aqua regia dissolves gold, 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 ions to produce tetrachloroaurate(III) anions, also in solution. The reaction with hydrochloric acid is an equilibrium reaction that favors formation of chloroaurate anions (AuCl4−). This results in a removal of gold ions from solution and allows further oxidation of gold to take place. The gold dissolves to become chloroauric acid. In addition, gold may be dissolved by the free chlorine present in aqua regia. Appropriate equations are:
Au + 3 HNO+ 4 HCl
3[AuCl
]
4−+ 3 [NO] + [H
2O]
3++ 2 HO
2
or
Au + HNO+ 4 HCl
3]
4−+ [NO] + [HO]
3++ HO
2
If the aqua regia solution only contains gold, solid tetrachloroauric acid may be prepared by boiling off excess aqua regia, and removing residual nitric acid by repeatedly heating with hydrochloric acid. That step reduces nitric acid (see decomposition of aqua regia). If elemental gold is desired, it may be selectively reduced with sulfur dioxide, hydrazine, oxalic acid, etc.[6] Appropriate equations are, for example:
2 AuCl−(aq) + 3 SO
4(g) + 6 H
2O (l) → 2 Au (s) + 12 H
2+(aq) + 3 SO2−(aq) + 8 Cl
4−(aq).
Evidence based speculation, page-38
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