Cupelling Karat Gold

[gbrideau]

Hi forum members,

I can't seem to be able to find much information about cupelling karat gold, as in 10k rings, for example. At what temperature should I cupel a 10k gold ring? I've noticed a few posts mentioning that gold should be cupelled at a temperature between 1700f to 1850f but since this is below the melting point of gold, wouldn't the button freeze in the cupel as the gold gets more pure before all the lead has been removed? Any help would be greatly appreciated. Thanks!

 

[Yggdrasil]

Why are you wanting to cupel 10k Gold?
Cupelling is almost exclusively used for assaying ores and such to determine if it has Gold in it.
10k Gold will most likely have both Silver and Copper in it, Silver will stay in there and Copper is very hard to get out, it needs a lot higher temperature than Lead.
So what are you planning to do?

 

[gbrideau]

This is mostly to remove base metals and to be left with precious metals. I've seen it done on youtube where the person cupelled 5+ grams of 14k gold along with 30 grams of lead and all copper was virtually removed as per the XRF results before and after. I'm just wondering how the temperature works.

 

[Yggdrasil]

This is mostly to remove base metals and to be left with precious metals. I've seen it done on youtube where the person cupelled 5+ grams of 14k gold along with 30 grams of lead and all copper was virtually removed as per the XRF results before and after. I'm just wondering how the temperature works.

It is doable, but it is not sure it is economic or environmentally viable.
If your plan is to get the Gold and Silver out. The easiest is to add a bit of preferably Silver or Copper to bring the karat to 6. Then part it with Nitric and collect the Gold and Silver separately. Slightly more than this but basically it. Cupelling is also slightly more involved and after you need to part it anyway.
Youtube is not a very reliable source of information. There are good videos, but few and far between them.

 

[gbrideau]

Thanks for getting back,

Yes, I'm very familiar with inquartation and the aqua regia method. However, nitric acid is not readily available here in Canada and is quite expensive. It is something I will look into in the future once I'm able to build a proper lab with a fume hood, etc. Thanks!