Gold not precipitating after showing with stannous chloride
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Hi Martijn , thank you for your interest. Hydrometallurgy has been my hobby since I was 10 years old ,I am now 75 . I have never had a bored day in my life.
Sodium thiosulphate is used to take Chlorine out of Tap water that is used for fish Aquariums . AuCl minus Cl gives you Au . Pardon my chemistry but I am a meat and potatoes type of Chemist.
From my observations of swimming pools in the old days HCl was used to treat pool water , but when I swam my nose and eyes always burned from the Chlorine gas on the surface of the water. When Mueric acid does not let off Chlorine gas come off pool water
but the Pool has to be drained 2 times a year to get rid of rezidual acid in the pool .
So excess Chlorine gas in your leach will redesolve your precipitated gold .
Martijn
Well-known member
Thanks for the explanation. Makes a bit more sense now.
So the sodium thiosulphate removes free chlorine out of solution and also reduces the gold chloride?
But I don't think excess Chlorine gas is an issue in this case, or with AR. It's an excess of nitric he's dealing with.
And having urinated in it.
And treating black sands with AR.
So the sodium thiosulphate removes free chlorine out of solution and also reduces the gold chloride?
But I don't think excess Chlorine gas is an issue in this case, or with AR. It's an excess of nitric he's dealing with.
And having urinated in it.
And treating black sands with AR.
Dear Martijn, Yggdrasil and all respected members
Thanks a lot ai have got my gold in hand , I have done as you advised.
1. I took 45 kg of sand and make it concentrated using Sluice box and then shaking table, it becomes 4 kg approx
2. I have added 3 litre HCl in a beaker with sand and heated it at 40C then I started using nitric acid drop by drop in the beaker and I have used 30 ml max and the reaction has stoped.
3. Then I have filtered the AR and tested for gold with stannous chloride it shows very good purple black. then I have added sulfamic acid in it till reaction stops.
4. Then I took 250ml water and added 60 gram SMB in it and pour it in AR solution slowly and stir.
5. first solution become brown, then reddish brown then black, I leave for 4 hours and found the black precipitant, I filtered it and washed it 3 times with warm water and dried.The black powder came 8.6 gram.
6.Finally gone to smelting, I have added 10 gram borax, 10 gram sodium carbonate with black powder in crucible and smelted with torch, I was mad to see that I got 3.6 gram gold button( picture attached)
Thanks a lot to all members, yggdrasil and Salute to Martijn
best regards
Thanks a lot ai have got my gold in hand , I have done as you advised.
1. I took 45 kg of sand and make it concentrated using Sluice box and then shaking table, it becomes 4 kg approx
2. I have added 3 litre HCl in a beaker with sand and heated it at 40C then I started using nitric acid drop by drop in the beaker and I have used 30 ml max and the reaction has stoped.
3. Then I have filtered the AR and tested for gold with stannous chloride it shows very good purple black. then I have added sulfamic acid in it till reaction stops.
4. Then I took 250ml water and added 60 gram SMB in it and pour it in AR solution slowly and stir.
5. first solution become brown, then reddish brown then black, I leave for 4 hours and found the black precipitant, I filtered it and washed it 3 times with warm water and dried.The black powder came 8.6 gram.
6.Finally gone to smelting, I have added 10 gram borax, 10 gram sodium carbonate with black powder in crucible and smelted with torch, I was mad to see that I got 3.6 gram gold button( picture attached)
Thanks a lot to all members, yggdrasil and Salute to Martijn
best regards
Attachments
You are welcome.
The preicipitant should have been boiled in HCl to get clean gold.
It seems like it is on the low side, I would do the whole thing again with the same concentrates.
Sometimes we have to add more HCl, but here I think you needed more nitric and heat. We mostly try to keep it as close to boiling as possible without boiling so around 90ish degrees.
For the most part at least me add the SMB as powder. Have you tested the solution after dropping the gold?
Some members prefer to drop the gold at pH 1.5
And there are no need to dilute unless to get rid of the lead and silver chlorides.
The preicipitant should have been boiled in HCl to get clean gold.
It seems like it is on the low side, I would do the whole thing again with the same concentrates.
Sometimes we have to add more HCl, but here I think you needed more nitric and heat. We mostly try to keep it as close to boiling as possible without boiling so around 90ish degrees.
For the most part at least me add the SMB as powder. Have you tested the solution after dropping the gold?
Some members prefer to drop the gold at pH 1.5
And there are no need to dilute unless to get rid of the lead and silver chlorides.
Well , try to run the cons again just to see if there is more.
Still 1g a kilo is not bad.
What do the assay say pr ton of ore?
Silver dissolves in nitric.
But it will also passivate the gold in AR if the concentration is high enough. Even worse if the gold is too high comparing to silver it can passivate the silver too.
If silver and gold is in alloy, it has to be inquarted, that means max 25% gold then nitric leach.
It can be overcome by mechanical stirring and such.
The case is: You need to know what is in there and in what form, this will decide the type of leach you can or should do.
Cynide derivatives will dissolve both silver and gold if I understand correctly.
What you need to do now. Find out where your gold is, leach the cons. Again first dilute nitric under strong heat. Then AR again.
Even better have the leached cons assayed again, if possible to see if there are values left. If so, you know where the gold is. If not you may just have been unlucky.
A side note, the precipitaded gold needs to be boiled in HCl to clean it properly. And if it is cinnamon coloured you really do not need borax to melt gold, sometimes a significant amount of gold get locked up in the borax, specially if it is not clean.
But it will also passivate the gold in AR if the concentration is high enough. Even worse if the gold is too high comparing to silver it can passivate the silver too.
If silver and gold is in alloy, it has to be inquarted, that means max 25% gold then nitric leach.
It can be overcome by mechanical stirring and such.
The case is: You need to know what is in there and in what form, this will decide the type of leach you can or should do.
Cynide derivatives will dissolve both silver and gold if I understand correctly.
What you need to do now. Find out where your gold is, leach the cons. Again first dilute nitric under strong heat. Then AR again.
Even better have the leached cons assayed again, if possible to see if there are values left. If so, you know where the gold is. If not you may just have been unlucky.
A side note, the precipitaded gold needs to be boiled in HCl to clean it properly. And if it is cinnamon coloured you really do not need borax to melt gold, sometimes a significant amount of gold get locked up in the borax, specially if it is not clean.
If you bring a clean metal to its liquid state, it is considered melting.
If you add fluxes for reduction, oxidation or other reasons its called smelting.
If the gold is clean, you just drop it in a crucible pre glazed with borax and melt it. Of course you need to take care so you don't blow your powder out of the crucible.
When the gold ball, solidifies just pick it up with a tweezer and drop it in water.
Martijn
Well-known member
Beatiful button! Looks like a nice pipe from what i can see. Especially from a dirty solution. Great result!
I must say again: AR is not the way to treat whole batches of placer concentrates.
Smelting is.
Now back to the beginning.
Did you improve on safety and equipment with this experiment? I sure hope so.
Besides silver you also have platinum in the concentrates. At 40 degrees Celsius some may have dissolved.
What did you do with the waste solution?
Did you test it with stannous?
Martijn.
I must say again: AR is not the way to treat whole batches of placer concentrates.
Smelting is.
Now back to the beginning.
Did you improve on safety and equipment with this experiment? I sure hope so.
Besides silver you also have platinum in the concentrates. At 40 degrees Celsius some may have dissolved.
What did you do with the waste solution?
Did you test it with stannous?
Martijn.
