How can I successfully precipitate gold from ore using aqua regia?

[happyprince]

Hi,
I can precipitate gold dissolved in aqua regia if the gold is just pure.I use sodium metabisulfite.However,if I dissolve the gold from ore in aqua regia,I cannot precipitate the gold.What's wrong?Might other metals or mud in the soil spoil it?Does anything prevent precipitating?Any help will be highly appreciated.Thanks a lot in advance.

 

[1bird9stones]

Try liquid-liquid extraction. You need an extracting solvent that has a high partition coefficient with gold (low partition coefficient with all others), but also doesn't irreversibly react with gold. The extracting solvent also can't mix with aqua regia. Hope this helped.

 

[JohnRC]

Hi,
I can precipitate gold dissolved in aqua regia if the gold is just pure.I use sodium metabisulfite.However,if I dissolve the gold from ore in aqua regia,I cannot precipitate the gold.What's wrong?Might other metals or mud in the soil spoil it?Does anything prevent precipitating?Any help will be highly appreciated.Thanks a lot in advance.

What are you meaning by gold ore? Usually "ore" means a crude compound of the metal you are seeking. Are you simply talking about soil or crushed rock with a decent content of elemental gold? Or are you in a region where the gold is obtained as telluride? (the only gold compound that is present in nature at a significant level).

I do not know much about the chemistry of telluride, and cannot help you further if that is the case.

If you are simply talking native elemental gold, then I think the most likely explanation is that most of the "gold" in your material is pyrite or similar material (marcasite, arsenopyrite, chalcopyrite) which occurs in conjunction with gold deposits, which can have very similar appearance to native gold, and which can make gold-bearing rock look much richer than it really is. These materials also dissolve in aqua regia, but do not precipitate anything when treated with bisulfite. However, there is one tell-tale sign -- a smell of rotten egg gas when you first apply the aqua regia.