Refining 10kt and 14kt Gold

What is everyone using to refine old scrap 10kt and 14kt gold such as old class rings, broken chains, etc. back to 24kt (.999 fine).

The general procedure is to treat with dilute nitric acid followed by the AR method.

Steve

can it be sodiom nitrate and hydro acid

Sodium Nitrate and HCl create Aqua Regia. But if you want to get all the pure gold, you must first dissolve the most of the silver with Nitric Acid. Silver in Aqua Regia will block the gold from getting out.

Inquartation is the key to success. Yellow karat gold that's 10K or greater is difficult to dissolve. The gold protects the base metal from nitric, and the silver protects the gold from AR----so you have to either raise the gold content above 90%, or lower the gold content to about 25%----which is somewhat critical. If you go too far below, it doesn't honeycomb, but breaks down into fine powder instead. That makes the separation of solids from the liquid most difficult because the gold stays suspended to some degree. Anyway, the process is to remove all the base metal, then to dissolve the remaining mass (most of which is gold), with AR, evaporate, filter then precipitate, using a selecting reagent so you don't contaminate the gold. It's real straight forward, but there are necessary steps that must be observed if you want high quality gold.

Harold

Is it possible, if you have 14k gold or higher, to melt it with copper (to lower it to 25%) then dissolving it in nitric acid ?
Thanks

Noxx said:

Is it possible, if you have 14k gold or higher, to melt it with copper (to lower it to 25%) then dissolving it in nitric acid ?
Thanks

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Yes, that works, but copper requires something like 300% more nitric to dissolve than does silver. That's yet another reason why anyone that plays with this stuff should be involved in refining, at the least, silver, gold, platinum, palladium, and even mercury, which is a great source of silver (dental amalgam).

When you're involved fully, you save your scrap silver and use it instead of copper, which is a dead end trail because of the greater nitric consumption, and the need for the copper to recover silver from solution. The silver, which is generally either coin or sterling, needs to be dissolved in acid anyway, so you accomplish two things at the same time. That's all a part of properly refining yellow and green karat gold, which is a world apart from extracting from plated items. Unlike those two, white gold could be directly dissolved in AR, but it's far better to remove the nickel beforehand by the same method (inquartation, then nitric), so the yield is of higher quality.

If you don't know, it's a high percentage of silver that makes gold green, although there's some copper there, too.

Harold

Harold,

The more I read and try to leard about the process of gold recovery, the more I realize just how importand the refining process is as well.

As a real newbie to the realm, it was my ignorance which made me think that these were 2 different subjects alltogether. This was illustrated in my comment about the naming of the domain that Noxx was asking about, and your subsiquent comment to my post at that time.

Realizing the processes go hand in hand (duh), just makes me realize just how much there is to learn on this subject.

Thanks,

Gary

Harold,
If you dissolve silver with Nitric Acid how it is possible to get it back (precipitation method) ?
Thanks

Noxx,

You could add a more reactive metal to the solution (i.e: Copper). The Cu will displace the Ag from the solution as a solid. Here's the whole chart:

Metal Activity Series

Metal Metal Ion Reactivity

--------------------------------------------------------------------------------
Most Reactive
Lithium
Potassium
Calcium
Sodium
Magnesium
Aluminum
Manganese
Zinc
Chromium
Iron
Lead
Copper
Mercury
Silver
Platinum
Gold Li+
K+
Ca2+
Na+
Mg2+
Al3+
Mn2+
Zn2+
Cr2+, Cr3+
Fe2+, Fe3+
Pb2+
Cu2+
Hg2+
Ag+
Pt2+
Au+, Au3+
Least Reactive

Any solid metal higher up in the chart will displace a dissolved metal lower in the chart from pure homogenous solutions. This is known as a single displacement reaction. Remember to check your resultant chemical MSDS before doing this. Copper Nitrate is the compound formed from by using copper, it remains in the solution when the silver has dropped out.

This holds true for pure solutions of silver nitrate which is what nitric acid converts pure silver into. If there are other acids or metals then you will possibly have other percipitants. I think there are some other compounds that will work as well. I'm sure Harold can add more to this.

Steve

Nitrate,

That makes perfect sense seeing how Sodium (Na) is at the top of the activity series. Thanks for the tip.

Steve

lazersteve said:

I'm sure Harold can add more to this.
Steve

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Chuckle!

Thanks for the very flattering comment!

Nope-----can't add much. I know those things, but not the way Steve does. I know them from the school of hard knocks-----he appears to know them because he's educated. Not the same thing.

The only comment I'd make here is that you generally process silver as a nitrate, and recover with copper. Instead of attempting to do a stoichiometric conversion, it's common practice to use an abundance of copper pieces (NOT WIRE) to recover the silver. Old buss bar or other copper components are very good for the purpose. The silver that is recovered by this method will be quite pure, but always contaminated with some copper. It is, however, high enough in purity that it can be melted and parted in a silver cell with good success.

It's important to not use excessive nitric in this process. If you do, it attacks the copper until it is mostly consumed, at which time it will start precipitating your silver. It wastes both copper and nitric. Also---the solution is better slightly diluted as compared to highly concentrated. When the solution is too concentrated, it's not uncommon for the silver to plate out so solidly that it adheres to the copper as a solid sheet and is very difficult to dislodge. The silver should come down as fine particles, as I describe below.

You don't use copper wire for recovery because as it is used up, it doesn't go away uniformly, and it's virtually impossible to recover all the bits that remain when the silver is completely precipitated as what is known as "cement" silver. It very much resembles Portland cement. Once it's finished, the solution should be checked for the platinum group, especially if it has a greenish tint. Allowed to sit long enough, all the platinum group metals that may be contained within will precipitate and hitchhike with the silver. to be recovered in the silver cell.

If, by chance, the solution is very dirty, it is often better to precipitate silver as chloride, using salt. The resulting chloride can be well washed and then converted to elemental silver via the use of aluminum and a little HCL.

Harold

gb10101 said:

Harold,

The more I read and try to leard about the process of gold recovery, the more I realize just how importand the refining process is as well.

Click to expand...

Frankly, it's everything. Steve has circumvented conventional refining by using cupels to purify his gold, and is doing one hell of a good job at doing so-----but it quickly becomes cumbersome unless you have huge cupels and a furnace.

Truth is, you can extract the gold and sell it to a refiner, regardless of the degree of purity-----but if you're wise, you continue to learn, and become that refiner. It opens so many doors that otherwise remain closed that it's difficult to explain to the uninitiated. Imagine your fun hobby turning into the refining source for local jewelers. There's always room for competent refiners, especially for the small operators. Large refiners aren't too kind to the small consumer. I've had several very unappealing dealings with major refiners, as have most of the benchmen. Treat them fairly and honestly, providing high quality gold and silver and they're yours for life.

As a real newbie to the realm, it was my ignorance which made me think that these were 2 different subjects alltogether. This was illustrated in my comment about the naming of the domain that Noxx was asking about, and your subsiquent comment to my post at that time.

Click to expand...

Well, it's a little more involved than that. I started right out making a few comments that I'm sure were less then pleasing to a few of these guys. None of it was meant as it sounded-----it came from the mouth (or fingers) of a guy that had extracted gold for years, but understood all too well that extracting the gold was just the beginning of the process, it was not the end. That, however, is true only for some individuals. As I stated, some may take great pleasure in simply extracting and selling. Nothing wrong with that----especially when it's not for me to tell others how to enjoy their hobby and their lives. However, if you've anything like me, you want to go all the way----to become not only a competent refiner, but the best damned refiner there is. I practiced that and was rewarded with an incredible reputation for quality and honesty. That may not be for everyone, however. Each must (and will) dance to the music they hear, and they will be just as right for them as I was for me.

Realizing the processes go hand in hand (duh), just makes me realize just how much there is to learn on this subject.

Click to expand...

A lot to learn, indeed! I've extracted gold and silver from high grade ores, using cyanide and bromine as an oxidizer (it was a complex ore), so in the process I had to learn about titration, had to build a ball mill and an agitation tank, plus a gasketed filter press. I have learned things that I, otherwise, would have never experienced. Gold refining (actually, precious metal refining) was likely one of the best things I've ever done with my time---and it was fun almost all the way. At the end I was burned out and very eager to sell. Working long, hard days, including Christmas day, gets old. People do, too! 8)

Thanks,

Gary

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You're very welcome, Gary. I hope the things I have to say will be of benefit to you.

Harold

so if you use aqua reagia ,using sodium nitrate and hydro acid
wont that be considered the same thing

it will disole the silver

you just got to filter it

When you dissolve silver with Aqua Regia, it will «hide» your gold and you won't be able to get it back.

I use to work with some wet chemistries in an industry using Nitric acid to strip polysilicon. It's well known that Nitric by itself won't work even though it attacks polysilicion because it quickly creates an Oxide layer which stops this attack. (Sounds very similar to this gold dissolving problem mentioned in this forum.)

To get around this you add a small amount of another acid which then strips the oxide. So this mix does the job very well.

Sorry but I decided not to mention this other acid because it's very, very dangerous and I don't want anyone that's a newbie to try and find this. If you spill it on you it attacks calcium (which means it likes blood and bones and will get absorbed through the skin). Definitely not for the faint of heart or someone that is not well trained with chemical hazards, spills, toxins, safety, etc.

Just curious if the same holds true when dissolving gold and using Nitric Acid? That the correct blend using a different and possibly high toxic acid would work.

Gold Digger,

Thank you for keeping this acid's identity a secret, it is in my opinon the deadliest of all acids. I refuse to work with it.

Some things should not be disclosed here.. ever.


Steve

have you ever tride this

aqua regia sodiom nitrate and hydro

after everything has come off filter your aqua regia using a med filter

all the silver will stay on the filter then add your participant to the liquid

to get pure gold

Nitrate has been kind enough to share some information with me citing a patented electrolytic cell design to process karat gold. I just want to let everyone on the forum know that I plan on designing one of these cells and posting my work with it under the tutorials section. I will post videos of the entire process as time permits.

Steve