Gold refining secret from karat jewelry

[SilverNitrate]

Ok this noob is telling his secret. But I will be brief and explain more later on.

Say you have a lot of jewelry gold, teeth, and even electronic teeth.

And you use AR (aqua regia).

My method is dissolve everything in AR, generally its diluted to 50% of the concentrated acids to keep down on the fumes. Leave it in the acids for at least 2 days. make sure nothing you use in your lab is made of metal--- only use plastic and glass.

filter the solution thru a buchner funnel into a bucket.

add in sodium hydroxide solution making sure all is dissolved (the solution should look purplish brownish, with no green. then let this set up for a day or two. Test by dipping in a piece of copper if it forms a layer, you need more hydroxide. other wise your pH meter should be well over 10.

Mix up some Caustic Syurp (aldose solution) this will make a dark fluff on the bottom (this is gold) there will still be gold dissolved in the solution.
stir this and wait another day

Titrate by pouring in conc. HNO3, the acid will immediately drop out the gold. The resulting copper and other metals will relain dissolved in the solution.

You sould get at least 99% of your gold processed with a purity I have consistently got it over 99% purity.

After you seperated and rinsed off your gold, that solution should be set aside in a bucket with an ingot of copper and closed up for at least a week. any other gold will be dropped out and collected later.

If you did this from karat jewelry, the sludge containing silver chloride and stones can be handled this way.---

Take that then mix it in a beaker with NaOH and heat for some hours (depending on how much) as to make the silver into oxide. until this a nearly dry mass.
Take outside and pour into a metal pot along with about 1/4 vol of dry sugar mix it then set it a fire with a match! after this burns you'll have pure silver!
Now take all the contents and dissolve in HNO3 to seperate the stones. now you have a silver nitrate solution which you can turn back into silver at a later time (see one of my other posts on processing that silver using the caustic syurp)
The stones can now be placed into a poly-propylene beaker of HF ---(yes the very deadly hydro-fluoric acid) this will dissolve the glass and lab made stones leaving behind only the pristene diamonds. anything else left will be small white worthless stones.



Disclaimer to anyone. This is for informational use only as this my method as from experience. I am well versed in the chemicals I use and know that some items can cause death if not properly handled. Other chemicals can permanently damage items. some process can potentially be a fire or explosion hazard.

 

[Harold_V]

My method is dissolve everything in AR, generally its diluted to 50% of the concentrated acids to keep down on the fumes. Leave it in the acids for at least 2 days. make sure nothing you use in your lab is made of metal--- only use plastic and glass.

While that can be effective on gold alloys that are low in silver, it will not dissolve gold that has excessive silver in its makeup. Green or yellow gold would likely resist fully dissolving due to the layer of silver chloride that forms on the solid pieces. If they're thin enough, that isn't the case, but if you attempt to dissolve jewelry in its original form, it would most certainly be a problem for heavy cross sections. How are you addressing the porting that won't dissolve?

You sould get at least 99% of your gold processed with a purity I have consistently got it over 99% purity.

Could you please tell us how you are assaying your yields to ascertain the purity?

some process can potentially be a fire or explosion hazard.

Yes, I agree, you are providing instructions that have the potential to be unnecessarily hazardous.

Would you please advise us why your method would be used in lieu of accepted practice, which is normally free of the majority of the hazards one may be exposed to with your system?

A good example that should be avoided when possible is working with concentrated basic solutions. They have the potential to instantly blind a person should some get in one's eyes. I survived exposure to tech grade nitric in that fashion, with no further consequences than a few days of discomfort. That's a far cry from being blinded.

Harold

 

[SilverNitrate]

While that can be effective on gold alloys that are low in silver, it will not dissolve gold that has excessive silver in its makeup. Green or yellow gold would likely resist fully dissolving due to the layer of silver chloride that forms on the solid pieces. If they're thin enough, that isn't the case, but if you attempt to dissolve jewelry in its original form, it would most certainly be a problem for heavy cross sections. How are you addressing the porting that won't dissolve?

silver chloride that is formed is semi-permeable meaning that with ample time the acids will leach out the gold... hence why it should be done over a period of days

Could you please tell us how you are assaying your yields to ascertain the purity?

I do this mainly as a hobby, refining the jewelry gold, though I am a PM broker as well, I likes to make high karat metals either to sell on market or into other chemicals.
When I sell gold I have to have it independently assayed and the lowest number I got is 99.19% and as high as 99.8% metal basis.

Would you please advise us why your method would be used in lieu of accepted practice, which is normally free of the majority of the hazards one may be exposed to with your system?

Refining gold is a more so a skill where as one's technique may differ from another to attain similar results. I find that the way I perform the method has less enviromental impact than other methods using AR. True there are the hazards but its the least hazardous way I have found thus far. One should always wear resistant gloves, face shield, lab-coat, work under a fume hood, and work close to a source of running water. Never take safety for granted.

The step involving HF acid is only used for recovering and identifying diamonds.

 

[Smitty]

For anyone that is considering using HF in their experiments, please be extra careful since a regular water wash will not cure HF exposure on skin. Exposure to HF because it contains Flourine will require an injection of Calcium done by a physician.

You may want to invest 75 dollars in a diamond/moisanite tester. It's hard to test stones if they are too small using the tester also.

It's also nice to hear that there are other options used for processing.

 

[Harold_V]

silver chloride that is formed is semi-permeable meaning that with ample time the acids will leach out the gold... hence why it should be done over a period of days

Having refined gold for well over 20 years, using the inquartation and AR process, I found that once you form a layer of silver chloride on gold, it becomes impervious. There's a delicate balance where the gold and other metals go into solution before the impervious layer can form. It could very well be that your process doesn't allow it to form, although I can't imagine it is a function of time. I've boiled in AR, for hours, gold that is high in silver as I've described, and it won't dissolve, nor will the silver chloride break down. It simply forms a thick layer and all action ceases.

I do this mainly as a hobby, refining the jewelry gold, though I am a PM broker as well, I likes to make high karat metals either to sell on market or into other chemicals.

When I sell gold I have to have it independently assayed and the lowest number I got is 99.19% and as high as 99.8% metal basis.

Thanks for that. While the numbers aren't bad, you're below the industry standard (9995), which I would not find acceptable. Depending on the contaminants, and the use of the gold, it could prove to be troublesome, and in some cases, costly, for the user. There are far better techniques that more or less insure quality. Proper handling in those cases is essential as well.. Anyone can produce inferior quality from the best of procedures if they aren't vigilant in following good practice.

I'm more than familiar with precipitating gold from dirty solutions. I processed bench filings by dissolving them directly in AR, although they received a hot nitric/water wash prior to dissolution. The quality of the gold that came from that process was never good. You can't expect clean gold when it's precipitated from dirty solutions. If for no other reason, drag down will contaminate it beyond an acceptable level, and often even prolonged washing in hot HCl won't improve it to an acceptable level.

Refining gold is a more so a skill where as one's technique may differ from another to attain similar results. I find that the way I perform the method has less enviromental impact than other methods using AR. True there are the hazards but its the least hazardous way I have found thus far. One should always wear resistant gloves, face shield, lab-coat, work under a fume hood, and work close to a source of running water. Never take safety for granted.

I certainly agree with your recommendations to wear protective gear, and to work in a fume hood. Still, some of the process you recommend are more trouble than using more commonly applied methods. None of them present any more hazards for the environment that those you propose, and are certainly much faster. Quality would be better, too.

For example, starting with a few ounces of gold, I can inquart, dissolve base metals and have gold dissolved and evaporating in less than two hours. I did that routinely. When pressed, a small amount of gold (a few ounces) can be processed totally in less than 24 hours.

When you have a large volume of material to handle, which I did, the idea if giving any of it the luxury of sitting for days while they quietly worked simply would be unreasonable. Still, I find your process interesting.

The step involving HF acid is only used for recovering and identifying diamonds.

There are certainly better methods that don't present the risk of handling HF. Remember, many of these guys are working with less than essential equipment. It's a good idea to refrain from making recommendations to use HF-----which can get most of these guys in trouble, which they may not recognize until the damage is done. Unlike nitric, it doesn't give you much warning, does it! :wink:

Harold

 

[Irons]

For anyone that is considering using HF in their experiments, please be extra careful since a regular water wash will not cure HF exposure on skin. Exposure to HF because it contains Flourine will require an injection of Calcium done by a physician.

You may want to invest 75 dollars in a diamond/moisanite tester. It's hard to test stones if they are too small using the tester also.

It's also nice to hear that there are other options used for processing.

HF will dissolve them too.

 

[SilverNitrate]

HF will dissolve them too.

generally any sizeable ruby emeralds or pearl would be removed beforehand. those teenie tiny diamonds that cheap jewelry have can be identified more quicky using HF.
I know the dangers of using HF and do not endorse its use. The fumes given off is as deadly as H2S or cyanide. Only the most advanced should consider its use for processing diamonds.

 

[SilverNitrate]

Thanks for that. While the numbers aren't bad, you're below the industry standard (9995), which I would not find acceptable. Depending on the contaminants, and the use of the gold, it could prove to be troublesome, and in some cases, costly, for the user. There are far better techniques that more or less insure quality. Proper handling in those cases is essential as well.. Anyone can produce inferior quality from the best of procedures if they aren't vigilant in following good practice.

In order to get gold pass 9995 fine the electrolysis will do, and still there is the time element.
Noone here has access to molten gold piped thru with chlorine gas (the commercial bulk process)

 

[Harold_V]

Thanks for that. While the numbers aren't bad, you're below the industry standard (9995), which I would not find acceptable. Depending on the contaminants, and the use of the gold, it could prove to be troublesome, and in some cases, costly, for the user. There are far better techniques that more or less insure quality. Proper handling in those cases is essential as well.. Anyone can produce inferior quality from the best of procedures if they aren't vigilant in following good practice.

In order to get gold pass 9995 fine the electrolysis will do, and still there is the time element.
Noone here has access to molten gold piped thru with chlorine gas (the commercial bulk process)

Yes, the Miller process. It should be avoided, much the same as HF-----it is, really, beyond the scope of the hobby refiner.

I routinely surpassed 9995 quality-----although I never claimed to achieve 9999. All done chemically. My gold would melt without a flux cover, showing no oxides. You may have seen this picture, which has been posted several times.

Harold

 

[Lou]

That's the Miller process if I remember correctly.

Never done it personally, but I could easily set up for it. Well, maybe not, I don't know offhand what pressure my regulator will go to for chlorine and it will have to be significant to account for the density of liquid gold.

I often thought about using it, but I deemed in impractical for my small amounts of gold. Now if I were processing 400 oz at a time instead of 4, perhaps then I'd consider it.



Personally, I'd keep away from the stuff if I were you lot and didn't have the proper gloves, respirator, and hood or nice teflonware Generally, if you work with dilute (10-20%) solutions it's fairly safe so long as you don't get any on you. The 70% and anhydrous HF are wicked nasty and fume just standing.

 

[lazersteve]

Title: Better hope there's no Emeralds, Rubies or Sapphires

Body:HF will dissolve them too.

Irons posting style is to include his title comment in his posts.

Nitrate,

Your process seems to require quite a bit of back and forth with HNO3. I see no need to increase the amount of HNO3 or my exposure to it when processing gold. As a matter of a fact, I'm all for never using nitric acid in my gold processing if at all possible. The same goes double for me and HF. There are cheaper and more easily accessible ways to dissolve your gold scrap and still achieve 'fine' gold.

Personally, I will not post any method or refining process that I can not endorse as useful to others.

Steve

 

[Irons]

I knew that. I was just giving a poke about other precious stones that would.

Separating Diamonds from gangue is another fun hobby.

I see plenty of tiny stones hereabouts. Too bad they're not worth much.

I was reading about a dead star recently that is mostly crystallized carbon. that would kill the market.

 

[Lou]

I'm going to have to read that post subject more closely from now on my friend. Sorry Irons! I goofed--I figured you knew better anyways.

 

[SilverNitrate]

I'm saying HF has nothing to do with the refining of gold. only to stain or dissolve non-diamonds after all the gold and silver has been processed.

an aquaregia made of HF / HNO3 will not work nearly as good as HCl / HNO3 ...have tried it and then had silica precititate to deal with in the end.

 

[Irons]

I'm going to have to read that post subject more closely from now on my friend. Sorry Irons! I goofed--I figured you knew better anyways.

Most of the time, I deserve it. :twisted:

 

[rockhammer53]

Hydrofloric Acid is VERY dangerous in any concentration. It burns throught the skin and seeks the calcium in the bones. We had 1 exposure in an industrial lab where a female tech was splashed with a 10% solution and recieved contact with less than 2 mL and can no longer use her right hand from the tissue and bone damage suffered. This is NASTY stuff and should be avoided at the hobby level ! This CANNOT be reversed... period ! This is a real danger to children and pets and in some states you can be held criminally liable for harming others with it ! YOU HAVE BEEN WARNED !!! :!: :!: :!:

 

[Harold_V]

I'm at a loss to understand how hydrofluoric acid relates to refining precious metals, particularly gold. None of the processes I used require it.

The warning is worth hearing, I have no quarrel with that.

Harold

 

[rockhammer53]

In the last 18 years of precious metals refining and electrowinning / electroplating the only place where HF was ever used was an etchant for Ti on a ceramic substrate in a High Tech lab.

I agree with Harold that HF has no place in this forum for any process or formula.

 

[Irons]

I'm at a loss to understand how hydrofluoric acid relates to refining precious metals, particularly gold. None of the processes I used require it.

The warning is worth hearing, I have no quarrel with that.

Harold

You cannot believe how painful a chemical burn from 70% HF is. We had a worker that used to open the bunghole on drums and take a sniff to see what was inside. He did that with a 55 Gallon Drum of 70% HF and it nearly killed him on the spot. He spent weeks in the hospital.

 

[Harold_V]

Very early in my learning curve, when I had less than an idea of the evilness of acids, I sniffed a container of HCl. Need I tell you that I learned a great deal from that experience?

As the old saying goes, when a guy picks up a horseshoe, straight from the hot coals of the forge, "it doesn't take me all day to look at a horse shoe".

Harold