Hello. I have read Hoke's book. I have lost 2 batches of gold and I do not want to loose another batch so I am asking for advice to make sure I am doing the correct procedure. I have a jar of gold foils with paper from the filters. When I rinsed the filter out I thought they were clean. I put them in a jar with the gold foils inside the paper filter. When the papers dried they were blue and green. Most of the paper has crumbled. There was fine gold flakes all over the paper, There were also small pieces of plastic in the foils. I burnt the papers thinking they would burn up and leave the gold behind. Well that did not work. Now I have a jar with gold foils, burnt paper and melted plastic bits. I was going to dissolve the gold by covering it with muriatic acid. Then slowly adding nitric. When all the gold is disolved I was going to add water and then neutralize it. then drop it with SMB. What I don't know is if the papers that were blue and green will adversely affect the drop. I recovered some of the gold with nitric acid. The rest of the gold was recovered from pins with muriatic acid. Thanks
Hoping to not loose 3rd gold batch.
- Thread starter Mousey
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Well as you have spent your time since joining studying I have to say well done.
In honesty you haven't lost your gold if you didn't throw it away, if you give us some details of what you did we can probably help you get your gold back.
As to your present material you can do as you described, simply wash the foils into a beaker add Hcl and then use the oxidizer of choice, with foils you can use bleach or peroxide and save the hard and often expensive nitric. The one advantage of using bleach which creates chlorine is that after the material has dissolved you can drive the excess chlorine off by heating the solution, this takes away the need to denoxx the solution as you would with nitric if over used.
Once you solution is cool filter it if need by several times until crystal clear, use the same filter paper then use the precipitate of choice.
Good luck and as I said relate what happened with your two other batches and we can try and help get your gold back.
In honesty you haven't lost your gold if you didn't throw it away, if you give us some details of what you did we can probably help you get your gold back.
As to your present material you can do as you described, simply wash the foils into a beaker add Hcl and then use the oxidizer of choice, with foils you can use bleach or peroxide and save the hard and often expensive nitric. The one advantage of using bleach which creates chlorine is that after the material has dissolved you can drive the excess chlorine off by heating the solution, this takes away the need to denoxx the solution as you would with nitric if over used.
Once you solution is cool filter it if need by several times until crystal clear, use the same filter paper then use the precipitate of choice.
Good luck and as I said relate what happened with your two other batches and we can try and help get your gold back.
Topher_osAUrus
Well-known member
The blue green is probably just copper chloride salts that were left on the filter from the initial leach filtrate. Maybe some of the solder mask from the boards.
Since you can never lose gold, I hope you saved your solutions.
How, or why, are you neutralizing the solution before smb precipitation? It needs some free HCl for the smb to release the SO2 gas, which is what reduces the gold. That could be why you "lost 2 batches", but you really didnt say much about those.
-unless by neutralize, you meant kill of the free nitric (deNOx the solution)
How did the incineration not work well?
It looks like you just needed to burn off a little bit more carbon. Either by turning up the hotplate a lot higher (after it was dried out), or hitting it with the torch. But, i suppose i need to ask how you incinerated?
Any more details or pictures you can share are always helpful
Since you can never lose gold, I hope you saved your solutions.
How, or why, are you neutralizing the solution before smb precipitation? It needs some free HCl for the smb to release the SO2 gas, which is what reduces the gold. That could be why you "lost 2 batches", but you really didnt say much about those.
-unless by neutralize, you meant kill of the free nitric (deNOx the solution)
How did the incineration not work well?
It looks like you just needed to burn off a little bit more carbon. Either by turning up the hotplate a lot higher (after it was dried out), or hitting it with the torch. But, i suppose i need to ask how you incinerated?
Any more details or pictures you can share are always helpful
Mousey, I've sent you a couple of Personal messages (PMs). Look for a link that says "Personal messages" and click on it.
Dave
Dave
kernels
Well-known member
Very good replies above, things to note: The HCl with foils should be heated to approximately 70 degrees Celcius or so before adding the Nitric Acid, the reaction of Aqua Regia is very slow at lower temperatures which could cause you to overdo the Nitric.
Secondly, you mentioned neutralizing, when really you only want to get rid of any excess Nitric acid, Sulfamic acid works well for this, or alternatively Urea, or as Hoke suggests, evaporate down and add HCl.
Oh, and . . . Gold is pretty much impossible to lose, it was 'made' by fusion in a astronomical (literally) explosion of a giant star and has been around ever since. Don't throw anything away, all the gold is still there somewhere.
Secondly, you mentioned neutralizing, when really you only want to get rid of any excess Nitric acid, Sulfamic acid works well for this, or alternatively Urea, or as Hoke suggests, evaporate down and add HCl.
Oh, and . . . Gold is pretty much impossible to lose, it was 'made' by fusion in a astronomical (literally) explosion of a giant star and has been around ever since. Don't throw anything away, all the gold is still there somewhere.
Hello I decided to use the hydrochloric acid and bleach method. I put in 400 ml of hydrochloriic acid and 100 ml of bleach. The breaker had 300 ml of gold and black paper flakes in it. I left the beaker over night with a rubber glove on it it keep the fumes down. The next day the jar was still full of gold . So I put the beaker on hot plate hoping to dissolve more gold. No help. I added more hydrochloric acid and bleach but there was no reaction.
Now I don't know what to do. I have the breaker on the hot plate reducing the volume of the bleach and hydrochloric acid at the moment.
Now I don't know what to do. I have the breaker on the hot plate reducing the volume of the bleach and hydrochloric acid at the moment.
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Topher_osAUrus
Well-known member
What kind of bleach are you using?
The cheap, plain Jane unscented stuff is the best.
When you added it, did it effervesce?
If not, the bleach may have gone bad and decomposed.
The black stuff may or may not cause you problems, its carbon from your filter papers. It can adsorb gold, or ot may even reduce it, and it can be a pain in the rear to rinse the auric chloride out of it.
Whats the pH of your solution?
How much bleach did you add?
Too much will make it go basic, and no gold will dissolve.
If the pH is still quite low, 1 or 2
Put the beaker in a corningware pyroceram pan, put it on a hot plate.
Turn the temp to low, add 5mL of bleach and stir and stir and stir.
After 20 minutes or so, add a few more mL of bleach.
Then after 20 or 30 minutes, check the pH, if its above 2 or 3, add some more HCl, not a lot, just enough to lower the pH again before adding more bleach. Once the foils are almost all gone, dont add sny more bleach, add a little more heat and keep up the stirring.
Warming the solution is a double edged sword, the bleach is releasing chlorine gas, which is what is oxidizing the gold. Chlorine being a gas, is less soluble in warm solutions, but, the reaction rate increases proportionally to the increased temperature. So its a balancing act of keeping the reaction rate up, keeping chlorine in solution, and keeping the solution acidic.
The cheap, plain Jane unscented stuff is the best.
When you added it, did it effervesce?
If not, the bleach may have gone bad and decomposed.
The black stuff may or may not cause you problems, its carbon from your filter papers. It can adsorb gold, or ot may even reduce it, and it can be a pain in the rear to rinse the auric chloride out of it.
Whats the pH of your solution?
How much bleach did you add?
Too much will make it go basic, and no gold will dissolve.
If the pH is still quite low, 1 or 2
Put the beaker in a corningware pyroceram pan, put it on a hot plate.
Turn the temp to low, add 5mL of bleach and stir and stir and stir.
After 20 minutes or so, add a few more mL of bleach.
Then after 20 or 30 minutes, check the pH, if its above 2 or 3, add some more HCl, not a lot, just enough to lower the pH again before adding more bleach. Once the foils are almost all gone, dont add sny more bleach, add a little more heat and keep up the stirring.
Warming the solution is a double edged sword, the bleach is releasing chlorine gas, which is what is oxidizing the gold. Chlorine being a gas, is less soluble in warm solutions, but, the reaction rate increases proportionally to the increased temperature. So its a balancing act of keeping the reaction rate up, keeping chlorine in solution, and keeping the solution acidic.
Topher_osAUrus
Well-known member
You should invest in some pH strips. They are cheap and pretty essential in what we do. Especially in waste treatment.
I'd guess your bleach has gone bad and decomposed to salt, water, and oxygen.
http://www.powellfab.com/technical_information/sodium_hypochlorite/decomposition_reason.aspx
I'd guess your bleach has gone bad and decomposed to salt, water, and oxygen.
http://www.powellfab.com/technical_information/sodium_hypochlorite/decomposition_reason.aspx
Kadriver has some good videos, look at this for example (positioned at the gold foil dissolving) https://youtu.be/2sZUAprS5KI?t=764
Look at how much bubbling there is when he adds just a few ml of bleach.
Göran
Look at how much bubbling there is when he adds just a few ml of bleach.
Göran
