precipitating gold from ore

[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.

[elementcollector1]

What ore are you using? Ores are notoriously rife with impurities; these may have interfered with the precipitation process somehow.

[happyprince]

thanks a lot for your reply...I do not know the chemical composition of the ore,but it can be quartz...

[elementcollector1]

thanks a lot for your reply...I do not know the chemical composition of the ore,but it can be quartz...

 

You mean quartz with gold in it?

Because if that's true, the quartz shouldn't affect anything, being similar to glass in chemical composition.

The only way I can think of gold not precipitating is if it formed a soluble complex ion with some other impurity. Try evaporating or (carefully!) boiling your solution to get it concentrated, and try again.

[John Cuthber]

I think you may be asking the wrong question. I wonder if something stopped the gold dissolving in the first place.

As a simple example, imagine the ore had lots of limestone in it. The limestone would react very quickly with the acid and there would be none left to dissolve the gold.

 

Also, how do you know there is gold in the ore?