Quicker refining of 375 9 carat gold

[Deceitful_Frank]

Hey fam I've done a quick search here and can't see this brought up before. What do you guys think are the real world downsides to simply treating 375 gold with nitric acid? I have a steady supply of 9 carat at a good price and would happily forgo adding silver or copper to inquart my gold. I know dilute nitric acid readily attacks 375 gold and clearly after treatment it will hold together nicely for washing but will the nitric not penetrate through and cause a low yield? Do you guys think this can be countered with extra treatments or hammering the gold thin or lots of heating?

I'm aware that presence of silver in the mix when you add the HCl and the HNO3 with cause problematic AgCl but UK 375 gold is about 15% silver to start I believe. I welcome your thoughts.

 

[FrugalRefiner]

I know dilute nitric acid readily attacks 375 gold and clearly after treatment it will hold together nicely for washing but will the nitric not penetrate through and cause a low yield? Do you guys think this can be countered with extra treatments or hammering the gold thin or lots of heating?

You've hit on one of the keys to your answer. The more massive the piece, the more likely a nitric leach might not reach the center. The thinner the piece, the more likely it will penetrate all the way through. When in doubt, hammer it out. Then give it a twist so it doesn't lie flat on the bottom of the beaker and the acid can reach it from all sides. In assaying, it's called creating cornets.

Dave

 

[Deceitful_Frank]

Thanks for the reply dave and yeah I really like the idea of giving it a twist. I often incinerate paper in my garden to save space in the recycling and have noticed that flat piles just tossed in to the flames hardly want to burn and can even put the fire out. Screw it all up into balls and it disappears in a flash!

Either way I would incinerate first to red heat to clean it up so may as wel treat al that relaxed annealed metal to a good hammering.

Great video by cody...
https://www.youtube.com/watch?v=aX4Iq11j2dI

Also I just read that once gold is over about 80% purity and has less than 10% silver, aqua regis will readily dissolve it. Just hoping that any AgCl formed will stay out of solution.

 

[FrugalRefiner]

In a strong chloride solution, there will always be a bit of silver in solution, as AgCl₂. You can eliminate most of it by diluting the solution, then filtering it, before you precipitate your gold. Proper washing will eliminate the rest. Plenty of information here about it.

Dave

 

[nickvc]

It all depends on the source of the 9 carat, if it’s British it needs inquarting, if it’s Italian straight to AR as there is no silver to worry about.

 

[goldenchild]

I sometimes thought about this when refining lower karat gold but just going straight to AR instead of nitric. If you could get a roller and roll the gold super thin you could probably go straight to AR no matter what you were dealing with. The plan would be to melt the scrap and pour it into a rectangular mold. Then create gold ribbon out of it. How much work it would be IDK but in my head I thought it would work.