Non-Chemical Stirring molten gold advice (XRF)

[davewilson24]

hello, I have recovered some gold today from some old bits of scrap i have collected, rolled and plated. I used nitric acid and was left with honeycome shells of gold,which was nice. I then melted my bits of dried out gold and made a little button of 11 grams. Here is where i got stuck, I went to the local gold buyers and they performed an XRF test and it came out at 40% gold on the one side of the button and 20% on the other. they did buy it of me but a 30% gold content. which i felt was fair as its the 1st time iv tryed it. is there any advice you can share for getting it mixed up equaly, ie a quench after heating? any help will be nice as im about to melt a kilo of 9ct and want the drill assay to be correct. many thanks in advance.

 

[qst42know]

I can't say for certain but a nitric digest properly washed, digested in AR or HCL/Cl dropped and then rinsed as prescribed should have been in well in the high nineties, 99.5% plus. If you follow known operations accurately there's not going to be any doubt.

You may have got stuck alright, buy an assay. It's better than getting bent over. Not getting raped on a kilo the cost is worth it. Clean gold you can heat as long as it takes to get it mixed, and GSP's rates are very fair. Cheap insurance to be treated right.

 

[Buzz]

Dave,

Did you refine the Gold after your Nitric bath or just melt the bits of scrap that were left?

Buzz

 

[qst42know]

Sorry, I jumped to the conclusion that you had finished the refining. I am assuming that you did not?

 

[eeTHr]

If there were no lumps in the honeycomb, shouldn't it still be way more than 30% average though?

 

[Buzz]

The Nitric took away the base metals, leaving behind karat Gold of whatever alloy percent it is.
In the UK, most of our karat Gold is 9ct (37.5%).
If we assume the Nitric didn't get all of the base metal, 30% would be about right.

 

[Oz]

If you started with .375 gold as you are assuming and added nitric are you saying that the gold purity dropped to .300?

That would mean that either base metal was added or gold removed.

I don't get it.

 

[qst42know]

hello, I have recovered some gold today from some old bits of scrap i have collected, rolled and plated. I used nitric acid and was left with honeycome shells of gold,which was nice.

 

[LeftyTheBandit]

May I suggest that if you ever process 9ct jewelry that you in-quart your jewelry with either copper or silver to bring it to 6k (25% gold). This way the nitric will leave you with extremely high 90% + gold.

If gold is 25% of the alloy, nitric will work exceptionally well on the other 75% base metal. At 30% its hit/miss get it to 25% it will be worth your time and money.

 

[LeftyTheBandit]

any help will be nice as im about to melt a kilo of 9ct and want the drill assay to be correct. many thanks in advance.

If you do not in-quart this lot you will have a bad experience. Preferably use silver or sterling silver to add as your added metal to bring your percentage gold from 37.5% (9ct) to 25% (6ct) gold content. If your in a pinch, use copper.

Download Hoke's book, and look up inquartation. Follow the procedure exactly. It is simple and effective.

 

[eeTHr]

Hmmmm. If the gold left after the nitric was originally 9K, 37.5%, then honeycombed 9K would be greater than 37.5%. Possibly much greater.

And wouldn't the plated portions be even more likely to have been penetrated by the nitric?

:?:

 

[Buzz]

If you started with .375 gold as you are assuming and added nitric are you saying that the gold purity dropped to .300?

That would mean that either base metal was added or gold removed.

I don't get it.

When i did my first batch of rolled gold, i used hot Nitric to get rid of the base metals.
When the reaction stopped, i assumed that all the base metal had gone.
What had happened though was that the Nitric had been used up and some base metal remained.
It wasn't until i came to refining the Gold that i realised what had happened.

I now use lazersteves equation plus a little extra to be sure when calcalating how much Nitric to use.

When Davewilson24 posted the question, it suggested he had melted the gold shells without refining them.
I was thinking that if any base metal remained and he then alloyed his 9ct with the remaining base metal, he would get a low reading, lower than .375 anyway.

A lot of assumptions here, so i may be way off the mark!

Buzz

 

[lazersteve]

I agree with Buzz.

The nitric process was not driven to completion and the gold was not properly washed and refined after the nitric process.

These two errors would result in gold of lesser purity than the starting material due to contamination carried over into the melt.

The major culprits for the source metal of contamination were likely copper or silver. I would guess some silver was cemented by copper remaining from the incomplete nitric dissolution. This silver was then melted in with the unrefined gold, lowering it's karat further.

If the nitric reaction was actually completed, then silver chloride (from using tap water) mixed with the gold may have contributed to the lowering of the karat.

Steve

 

[eeTHr]

This is very interesting. I'm trying to visualize the honeycomb shells.

I used nitric acid and was left with honeycome shells of gold,which was nice.

If there were no lumps in the honeycomb, shouldn't it still be way more than 30% average though?

Buzz, did you happen to notice if there were lumps within yours?

I'm thinking that, to arrive at 30% Au altogether, you would need to have more than twice as much silver and/or base metal(s) than gold in the resulting button. If that was all intertwined within the honeycomb itself, wouldn't that show visually? I mean, if there was now 70% "other" metal(s) within the honeycomb, either not dissolved or cememted into the spaces provided by any dissolved "other" metals, there would only be enough room within those spaces to bring it back down to 9K, or 37.5% Au total. The remaining 62.5% "other" metal(s) which ended up in the button would need to have come from outside of the honeycomb.

It seems like if it somehow cemented to the Au, it would more than cover the honeycombed Au shapes with a very non-golden-brown color.

Of course, if the "other" metals totally filled any spaces left after they dissolved, then the remaining jewelry shapes would no longer be "honeycomb," either. If the remaining shapes actually were honeycomed, wouldn't that mean even less "other" metals? Or the other metals could have been in powder form in the bottom of the container.

Hmmmmm. :?:

Unless there were some solid lumps of other metals left inside the outer shapes, from when the nitric stopped working.

davewilson24: A powder and lump report would be good here.

Of course, my line of thinking could be totally off track. 8)