Using ammonium chloride to 'remove' oxides

[Amol Gupta]

Reading across the forum I found references of using ammonium chloride to remove base metal oxides from refined gold.

The addition is always done as the gold is transitioning from the solid state to liquid or solidifying from liquid state to solid.

I was curious as to why is this done during the transition phase(solid to liquid and vis-a-vis) and not a steady state(when the gold is molten in the crucible).

Also my reading suggest this would only remove the base metal oxides, does it remove silver as well....?

 

[Yggdrasil]

Reading across the forum I found references of using ammonium chloride to remove base metal oxides from refined gold.

The addition is always done as the gold is transitioning from the solid state to liquid or solidifying from liquid state to solid.

I was curious as to why is this done during the transition phase(solid to liquid and vis-a-vis) and not a steady state(when the gold is molten in the crucible).

Also my reading suggest this would only remove the base metal oxides, does it remove silver as well....?

I think you misunderstood.
Ammonium Hydroxide can dissolve many things including Silver Chloride.
If you suspect Silver Chlorid it is essential to acidify as fast as possible after.
I have never heard that Ammonium Chloride can do this.

 

[Amol Gupta]

I think you misunderstood.
Ammonium Hydroxide can dissolve many things including Silver Chloride.
If you suspect Silver Chlorid it is essential to acidify as fast as possible after.
I have never heard that Ammonium Chloride can do this.

I'm talking of ammonium chloride being used as flux

 

[Yggdrasil]

I'm talking of ammonium chloride being used as flux

Never heard about that either.
I can’t quite see how the Chloride should be able to remove Oxides though.
Do you have a link?

 

[Amol Gupta]

Never heard about that either.
I can’t quite see how the Chloride should be able to remove Oxides though.
Do you have a link?

Post in thread 'Flux for Making a gold bar' https://goldrefiningforum.com/threads/flux-for-making-a-gold-bar.5416/post-46481

This for one along with many others.

 

[Dreamer]

A sprinkling of Ammonium Chloride will give the surface a concentrated flash of chlorine greatly improving its luster when applied during the transition from molten to solid. The large industrial refiners actually bubble chlorine through thier material capturing the chlorides in the slag (Miller Process). I don't really have any more knowledge on this but maybe it will give you a lead to pursue the answer.

 

[Yggdrasil]

Post in thread 'Flux for Making a gold bar' https://goldrefiningforum.com/threads/flux-for-making-a-gold-bar.5416/post-46481

This for one along with many others.

This thread goes around cleaning up Gold from the Miller process.
And as you see if you read further is that it is used to improve the finish of the Gold not its purity.
The Gold is covered in a blanket of Ammonium Chloride which makes it look more fabulous.

 

[Amol Gupta]

This thread goes around cleaning up Gold from the Miller process.
And as you see if you read further is that it is used to improve the finish of the Gold not its purity.
The Gold is covered in a blanket of Ammonium Chloride which makes it look more fabulous.

That is the reason for the word remove being in quotes.
I'm not really sure what is happening but I'm really fascinated as to why such an operation takes place only during the transition phase and not during the molten state.

 

[Yggdrasil]

That is the reason for the word remove being in quotes.
I'm not really sure what is happening but I'm really fascinated as to why such an operation takes place only during the transition phase and not during the molten state.

It does not.
It only polishes the surface.

Have you read the whole thread?

 

[Amol Gupta]

It does not.
It only polishes the surface.

Have you read the whole thread?

That is not the only thread mentioning this process there are quite a few more.

 

[Yggdrasil]

That is not the only thread mentioning this process there are quite a few more.

Yes but if you read the thread it is not recommended and you need some serious scrubbing of the gases.
Why du you want to use this method when you do notvrun a Miller process?
Anyway after the Miller process one usually go to a electrolytic cell.

 

[Amol Gupta]

Yes but if you read the thread it is not recommended and you need some serious scrubbing of the gases.
Why du you want to use this method when you do notvrun a Miller process?
Anyway after the Miller process one usually go to a electrolytic cell.

Of all the reading I've done this far I've never come across an instance where a reagent is added specifically during the transition phase I really don't look at it as a process I would perform but I'm curious as to the reactions involved.

 

[Yggdrasil]

Of all the reading I've done this far I've never come across an instance where a reagent is added specifically during the transition phase I really don't look at it as a process I would perform but I'm curious as to the reactions involved.

I really do not know.
It is not a process that is used much, if at all and as it is said in the thread you linked to, nor is it recommended.