# melting gold in furnace



## Anonymous (Jun 29, 2008)

So its no way silver, aluminum, lead,or any other alloys will evaporate out of the gold if your melting at a very high temperature or extending the amount of time your melting with a high powered electric furnace? Where do I find the wikipedia?

Thanks for the info
Mike


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## jimdoc (Jun 29, 2008)

Go to wikipedia.org


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## Harold_V (Jun 30, 2008)

michaelT said:


> So its no way silver, aluminum, lead,or any other alloys will evaporate out of the gold if your melting at a very high temperature or extending the amount of time your melting with a high powered electric furnace? Where do I find the wikipedia?
> 
> Thanks for the info
> Mike


There are minor exceptions such as cupellation, but you are not relying on heat alone----you are oxidizing the lead, which is then absorbed, along with oxides of other base metals, in the cupel. One does not purify precious metals simply by heating. If you introduce chlorine to the molten metal, that's a whole different world. It's called the Miller chlorine process.

Note that you can also eliminate zinc by heating. 

Harold


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## Lou (Jun 30, 2008)

Well, actually you can distill metals from one another and separate by vapour pressure alone, but it's stupid and thermally intensive. Which means it is expensive. It has no place in refining or unless it is mercury amalgam or maybe distilling zinc from the Parks process (which frankly is better done by parting with HCl).


However, it has been said that many metals dissolve in one another, giving you alloys or intermetallics. Systems get complex at that stage and at those temperatures. You'd better not go there.


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## Harold_V (Jun 30, 2008)

Lou said:


> Well, actually you can distill metals from one another and separate by vapour pressure alone, but it's stupid and thermally intensive.


Yep, I agree. It's well beyond the capabilities of the common electric furnace, which is the case in this example. Even reading about the Miller process raises hair on the back of my neck. Not much room for error, and generally beyond the capabilities of most home shop types. 

Folks need to learn about chemical refining to avoid chasing their tail.

Harold


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## Wyndham (Jul 12, 2008)

Just a quick question on bone ash cupels Harold and others. I use bone ash in several pottery glazes and the benefit seems to come from the extra oxygen in the phosphate ca?po3 I think this is correct ), anyway. Is this where the lead and other non gold items in the melt gets the oxidation. It seems the po3 adds oxygen to my iron in my glaze firing to keep it from natural reduction and keeping the color a brighter rusty red in my glaze(which I want). Wyndham


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## Harold_V (Jul 12, 2008)

Wyndham said:


> Just a quick question on bone ash cupels Harold and others. I use bone ash in several pottery glazes and the benefit seems to come from the extra oxygen in the phosphate ca?po3 I think this is correct ), anyway. Is this where the lead and other non gold items in the melt gets the oxidation. It seems the po3 adds oxygen to my iron in my glaze firing to keep it from natural reduction and keeping the color a brighter rusty red in my glaze(which I want). Wyndham


Cupelling is normally accomplished in a cupel furnace, where there is a constant supply of fresh air. Cupel furnaces are quite different from melting furnaces. It's been years, but I think they refer to them as muffle furnaces. Could be wrong. I never got involved in assaying, and cupelled only a few times, using a torch, not even in a cupel. It's an amazing process!

Harold


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