Non-Chemical Over boiled AR

[Phoebe]

Hi all, I’m new here. I need some help and clarification.
Previously I had refined 20 karat of gold using AR. During the AR process, I have over boiled the solution without notice and become almost dry up. Will I lost most of the gold from the brown fumes?
Kindly advice and thanks in advance.

 

[butcher]

Boiling you will lose some gold by spiting of the solution, if Gold chloride salts are heated strongly some of your gold can go up in a cloud of smoke,

You do not want to boil a solution of gold, you just need some heat to get more volatile of the solution to turn into a gas and evaporate.

In Hoke's book, she used the term to boil or boiling the solution.
She did use the wrong term in her book to describe the process when she was actually describing evaporating.
She used a steam bath (to do what she described as boil" the solution).
A steam bath will not get the aqua regia hot enough to "boil" and thus lose gold, the steam bath will only get warm enough to evaporate the solution, and not letting it get hotter and actually boil the solution.

You should be able to wet your salts in HCl to get them to dissolve, if you cooked the gold salts hard you may find that you also need to add a little oxidizer to get the gold back into solution.

Do not heat the solution enough to make it boil.
Use only enough heat to get the evaporation process started.

 

[Phoebe]

Thanks for your reply butcher,
But if I didn't heat it up long enough, it seems like the gold hardly can be 'eaten' by the solution.
I can still see the silver chloride layering on the karat gold. Any idea on how to rectify this situation?

 

[butcher]

If silver of the alloy is a problem for aqua regia, we normally add silver to lower the gold content of the alloy, then use nitric to separate the gold and silver before moving on to aqua regia with the gold.

Heating the solution is not a problem as long as you do not "boil the solution where the popping bubbles of gases escaping the solution so fast that it carries gold along with it. We often use heat to speed a reaction or to help dissolve hard to dissolve metals like platinum, we just do not need to actually boil the solution.

The silver crust can sometimes be broken mechanically with a glass stir rod or another method.

The silver chloride can be dissolved in another solution, but this normally causes other problems to deal with.

 

[Phoebe]

Thanks for the advice. Will keep that in mind. :wink: