Hello everybody. I apologize if you have surely already talked about the subject over and over again but I can't find a post that gives me the answers I'm looking for. I am a jeweler and have tried several times to get pure gold with AR from 18kt gold jewelry but with poor results, sometimes losing a lot of gold. as I said I would like to use both yellow and white 18 kt gold to obtain pure gold without loss of material. I had followed the classic patterns of AR, ice and then SMB. I tried to use both whole objects and sheets of a few mm thick. what am I wrong? is it necessary, using 18 kt gold, to quarter the gold? I'm here to ask for your help. thank you and sorry for my school english
I need help to refining gold
- Thread starter Luca.83r
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Start with the book in my signature line below. It was written for jewelers who wanted to refine their own scrap.
Depending on the alloy you start with, you may need to inquart.
You say that you have lost gold. Remember that you never really lose gold unless you throw it away. It's there somewhere, either in the solutions or the undissolved material. You'll need to give us more details about your process for us to help figure out what you've done wrong.
Dave
Depending on the alloy you start with, you may need to inquart.
You say that you have lost gold. Remember that you never really lose gold unless you throw it away. It's there somewhere, either in the solutions or the undissolved material. You'll need to give us more details about your process for us to help figure out what you've done wrong.
Dave
thanks for now.
I will definitely read your book! as I said I use jewelry and jewelry parts in 18kt yellow or white gold, I can't say exactly the composition of the alloy.
the procedure I used was: create a 2mm thick sheet, put it in the container, add 1 part of nitric acid and 3 parts of hydrochloric acid, heat, when almost all the material was dissolved (I had some silver-colored residues at times) I filtered , I rinsed the filter, I added ice, I added SMB, I eliminated the excess liquid and I heated the gold dust until all the liquid part was eliminated. Then I melted.
unfortunately, I am talking about 1 year ago, I threw out all the excess liquid
I will definitely read your book! as I said I use jewelry and jewelry parts in 18kt yellow or white gold, I can't say exactly the composition of the alloy.
the procedure I used was: create a 2mm thick sheet, put it in the container, add 1 part of nitric acid and 3 parts of hydrochloric acid, heat, when almost all the material was dissolved (I had some silver-colored residues at times) I filtered , I rinsed the filter, I added ice, I added SMB, I eliminated the excess liquid and I heated the gold dust until all the liquid part was eliminated. Then I melted.
unfortunately, I am talking about 1 year ago, I threw out all the excess liquid
I expect the missing gold was in the material that did not dissolve since you said "almost all the material was dissolved". We inquart gold alloys because silver in the alloy can cause problems. When it exceeds around 10% it can form an impenetrable crust of silver chloride. There can be undissolved gold alloy within that crust.
Before you threw the excess liquid away, did you test it with stannous chloride?
Dave
Before you threw the excess liquid away, did you test it with stannous chloride?
Dave
Most 18k alloys have low silver content , but white alloys can have palladium , so going straight to AR should work but you need to dissolve all the metal . Once you have precipitated your gold do a stannous test on the remaining solution for palladium , as you are in italy I think your alloys will be spot on so you shouldn’t have any losses .
If you use 3:1 premixed AR, you are probably using excess of nitric. And that is a problem, when you do not eliminate it before.
You need to add de-noxing step before gold precipitation with SMB. Hoke in book used old fashioned but bulletproof evaporation technique. But this is lengthy and very hard on equipment, as lots of acid vapor goes to the fume hood.
Now, we use sulfamic acid to accomplish this. You add sulfamic acid to at least 75°C hot solution very slowly and observe the fizzing - fizzing means you have excess nitric acid in solution. Add slow, or it will foam over. Use at least 3 times bigger beaker than needed - to be sure that it wont foam over. As it stop fizzing by last addition, let it heat for 15 minutes at same temperature and then add another bit of sulfamic acid. If it fizz, add until it stops. If it does not fizz after that 15 minute heating, you are done and you can let it cool down and proceed with filtration and SMB gold drop.
There was excellent thread where Harold and I think GSP (??) exchanged their overwhelming experience on refining karat gold to 99,9+. But unfortunately, I cannot find it. Maybe someone help to give a link to this.
You need to add de-noxing step before gold precipitation with SMB. Hoke in book used old fashioned but bulletproof evaporation technique. But this is lengthy and very hard on equipment, as lots of acid vapor goes to the fume hood.
Now, we use sulfamic acid to accomplish this. You add sulfamic acid to at least 75°C hot solution very slowly and observe the fizzing - fizzing means you have excess nitric acid in solution. Add slow, or it will foam over. Use at least 3 times bigger beaker than needed - to be sure that it wont foam over. As it stop fizzing by last addition, let it heat for 15 minutes at same temperature and then add another bit of sulfamic acid. If it fizz, add until it stops. If it does not fizz after that 15 minute heating, you are done and you can let it cool down and proceed with filtration and SMB gold drop.
There was excellent thread where Harold and I think GSP (??) exchanged their overwhelming experience on refining karat gold to 99,9+. But unfortunately, I cannot find it. Maybe someone help to give a link to this.
no, before I was not aware of the stannous chloride test and this was definitely my huge mistake. So do you think I shouldn't quarter gold?
Thank you, i will try
What do you plan on. using the gold for? Are you a jeweler and intending to make it into new jewelry?
If that is the case, the easiest path is to inquart with silver. The gold never dissolves and you can clean it up to 99.5 purity with nitric parting. Unless the gold pieces you process have platinum findings which will contaminate the gold, you can safely assume the contaminants in your semi refined gold are copper and silver. Adding additional silver and copper to make your desired karat alloy will allow you to recycle the gold back to jewelry easily.
A plus is you can re-use the same silver over and over and silver dissolves in nitric acid efficiently so there is less waste.
If that is the case, the easiest path is to inquart with silver. The gold never dissolves and you can clean it up to 99.5 purity with nitric parting. Unless the gold pieces you process have platinum findings which will contaminate the gold, you can safely assume the contaminants in your semi refined gold are copper and silver. Adding additional silver and copper to make your desired karat alloy will allow you to recycle the gold back to jewelry easily.
A plus is you can re-use the same silver over and over and silver dissolves in nitric acid efficiently so there is less waste.
no, I buy and sell, I don't create jewels and I don't repair them. I need pure gold to exchange for new jewelry from the retailer.
In the start of the thread you stated that you are a jeweller, now that you do not create or repair jewellery. I do not understand, but it does not change anything in the refining issue.
Define pure gold. How pure you need it ? 99% ? 99.9 % ? There are much simpler methods for lower purity gold - like 4metals said, simple inquartation+nitric leach can give you 995 gold. If you take this 995 gold and refine one more time with AR/SMB, you can easily get 99,9+% gold. But it is an extra step need to be done. You can go to 99.9% also by just dissolving the 18k feed in AR and then deNOxing and precipitating with SMB - altough it is sometimes tedious, when you have Ag-rich alloys (silver chloride blocking access of acid to gold).
Orvy I am a jeweler, I buy and resell jewels, I don't do repairs. I use a laboratory for these things. I need to get 99% pure gold to give to my dealer in exchange for new jewelry. so, reading what you wrote to me, I will try again with AR. how can i deNOxing easily and effectively? With sulfamic acid?
Yes sulfamic acid will do the trick, I wrote how to do it in the reply above.
A lot of us chemistry nerds here on the forum really enjoy the chemistry and all of the different forms of metal recovery. And then there are those who are in if for the business. I guess you are in it for the business Luca. So why are you choosing to watch your gold disappear and use chemistry to bring it back? You have already seen that it may not always come back if you do something wrong.
That’s why when guys are in it like you are may be better off watching everything else but the gold disappear. That is what inquarting and parting can do for you. Dissolve the base metals and silver and keep the gold in sight. Plus you recover the silver all from one place and recycle it over and over. And since you only need 99% purity it is totally do-able.
Inquarting won’t work for everybody but for you it can and it can do it effectively using only one chemical, nitric acid.
yes, you're right, I do it for business, but chemistry has always fascinated me and it's nice to see gold disappear and then return it (if everything works without problems!). so I would like to learn the method perfectly and will read the book very carefully. So you say that by quartering gold and using only nitric acid I can get 99% pure gold?
For sure. You need to melt your scrap and the required quantity of silver together so it is homogeneous and pour it into water to get small shots to dissolve. Then add a mixture of 2 parts distilled water and 1 part nitric acid with heat to dissolve out the silver and base metals. When the reaction is complete the gold will remain. Filter it, rinse it, and again add nitric and distilled water but this time 1:1, acid to water. Heat it again and allow the acid to dissolve out any remaining base metals. If the shot you made was large, you may need to use a glass rod to break up the chunks to help the dissolve. (This is in both the first and second dissolve). Filter it again, rinse and dry the gold and then melt it for sale.
This should meet your 99% Gold requirement. The second acid is just to enhance and get any remaining base metals or silver to dissolve out of the gold. It will not be exhausted and can be diluted a little bit to make it 2:1 and reused for your next lot. The first acid will contain most of the silver so you can cement it on copper to recover it for re-use.
The beauty of this method is it will work on a few ounces of gold or many ounces. This is why it has appeal with small jewelers
reworking gold scrap or, like you, reselling it.
If your fascination with the chemistry still beckons, the end result of the semi-refining by inquarting is a great feedstock for an aqua regia refine.
Ok Thank you.
where can i find the correct amount of silver to use to quarter 18kt gold?
The goal with inquartation is to make one quarter of the alloy gold and the balance silver. For small lots, under 5 ounces of alloy total, all you need do is figure out how much gold is in the lot. Whatever that number is, add 3 times the expected gold quantity as silver.
Some will say you need to take into account the base metals and silver already in the alloy and while it cannot hurt to figure that out and adjust your silver addition accordingly but for small lots like you will likely process, just add 3 times the expected gold weight as silver.
Take care to remove any platinum findings like prongs that hold stones because the platinum will remain with the gold and lower the purity.
Melt the alloy and the silver together and stir it well and pour it into water to make it into grain for digestion.
That’s all that is involved. There are plenty of threads about recovering the dissolved silver for re-use on the forum.
Good luck.
Some will say you need to take into account the base metals and silver already in the alloy and while it cannot hurt to figure that out and adjust your silver addition accordingly but for small lots like you will likely process, just add 3 times the expected gold weight as silver.
Take care to remove any platinum findings like prongs that hold stones because the platinum will remain with the gold and lower the purity.
Melt the alloy and the silver together and stir it well and pour it into water to make it into grain for digestion.
That’s all that is involved. There are plenty of threads about recovering the dissolved silver for re-use on the forum.
Good luck.
So if i have 100gr of 18kt gold i use 300gr of silver?
