Unable to precipitate gold

[Malc84]

Hi all, I am new to this forum so hello . I am hoping that someone will be able to help me. I have followed the instructions from this post Gold Recovery Correctly exactly. I tested the gold solution as described, which instantly turned black. When it came to adding the sodium bisulfite there was no reaction, the liquid remained yellow, I continued to add sodium bisulfite hoping for a reaction however this didn’t happen and I overloaded it . I ended up with roughly a 1 cm layer of sodium bisulfite, not knowing what to do I added more hydrochloric acid. I now have roughly 4cm of crystals in the liquid. The solution still tests positive for gold but I don’t know how to extract the gold.

Any suggestions/help would be greatly appreciated!

Thanks,
Malc

 

[Martijn]

Welcome to the forum.

https://goldrefiningforum.com/threads/when-in-doubt-cement-it-out.30236/
How much plated items did you dissolve to begin with? How much foils did you have?

Martijn.

 

[galenrog]

Sodium bisulfite? Why?

Time for more coffee.

 

[Malc84]

Thank you Martin. I started with 485g of ram fingers, I probably at a guess had around 4-5 grams of foils.
I have seen that I should have used sodium metabisulfite however I have also read that I can use sodium bisulphite, I know chemically they are different but without the necessary knowledge of chemistry I didn’t know what would happen.

 

[FrugalRefiner]

I have seen that I should have used sodium metabisulfite however I have also read that I can use sodium bisulphite, I know chemically they are different but without the necessary knowledge of chemistry I didn’t know what would happen.

Malc, welcome to the forum. I hope you find the information here to make you successful.

Now, I know this will be harsh, but if you don't have "the necessary knowledge of chemistry" to know what will happen, DON'T DO IT! Follow the tried and true processes detailed here on the forum. There are many ways to recover and refine precious metals. We recommended certain processes here because they are nearly foolproof. If you don't have a particular chemical described in a process here, substituting something that sounds close could kill you.

Dave

 

[Malc84]

Hi Dave, thank you for your response. The link I posted in my original post detailed everything I needed and he made reference to this site as his go to place for information so I followed it very carefully until I had no reaction to precipitate the gold, that’s where it seemed to go wrong even when following the instructions. If you could advise how to resolve this issue it would be greatly appreciated.

 

[Martijn]

From the article:
4. Stumpout by Bonide. or Sodium bisulfate - 99.9% as specified in the Msds or Sodium Meta Bisulfite

The second one mentioned, is wrong.
I did not read the rest for errors.
But it shows chemistry has to be exact. Little typo's can have big consequences or do nothing at all in the reaction.

Martijn.

 

[Malc84]

So it should have have been metabisulphite? Is there any way to reverse what I have done?

malc

 

[Stibnut]

Bisulfite and metabisulfite exist in an equilibrium with each other in solution, so it does not make a difference whether you use bisulfite or metabisulfite to precipitate gold. However if you used bisulfate, which the post you linked to seems to confuse with bisulfite, nothing would happen - that contains sulfur in the +6 oxidation state rather than the needed +4. So that's one possibility - make sure you have bisulfite rather than bisulfate.

Since you put a whole lot of the bisulfite in your solution, does it smell pungent, like burnt matches, burning sulfur, or volcanoes? This is sulfur dioxide and would indicate that you had the right compound. It's the release of sulfur dioxide in solution that does the work of reducing gold salts to the metal. If you can't smell any sulfur odor, this would be a good indication that you had bisulfate instead.

The other thing I noticed about the Instructables post is that they never heat their bleach + HCl solution or do anything else to drive off the excess chlorine after the gold is dissolved. If you have too much chlorine remaining in solution, gold will tend not to drop because it is re-oxidized and put back into solution by the chlorine. A similar thing happens with excess nitric acid in aqua regia. However, bisulfite is good at reducing chlorine to chloride so you likely reduced it when you added a large amount of it to your solution. For that reason I think this isn't your problem.

 

[Malc84]

Thanks for the above. I have rechecked and it is sodium hydrogensulphate that I have used, I believe this is the same as bisulphate. I have just ordered some sodium metabisulphite to use instead. Do you think I can just filter the liquid off to remove the crystals and then add the metabisulphite to drop the gold or do you think that the gold could have been locked into the crystals? If the gold could have been affected by me adding the bisulphate are there additional steps I need to take to remove it other than filtering it? Many thanks.

 

[orvi]

Thanks for the above. I have rechecked and it is sodium hydrogensulphate that I have used, I believe this is the same as bisulphate. I have just ordered some sodium metabisulphite to use instead. Do you think I can just filter the liquid off to remove the crystals and then add the metabisulphite to drop the gold or do you think that the gold could have been locked into the crystals? If the gold could have been affected by me adding the bisulphate are there additional steps I need to take to remove it other than filtering it? Many thanks.

Yes, you can filter the crystals, rinse them with some water.
Then you proceed with sulfite.

As Stibnut mentioned, it is relatively up to you which form of sulfite you use. You can use sodium metabisulfite (SMB), sodium sulfite or sodium bisulfite. Sulfur dioxide gas will also work perfectly.
If you cannot get some sort of sulfite, use ferrous sulfate for precipitation. It also work well.

"Nose testing" for SO2 is very easy, but SO2 is not healthy at all. Just be sure you do not stick your nose to the beaker, or it will knock you down pretty certainly. Very pungent smell, sulfurous, unbearable.
Learn how to properly sniff chemicals as chemist. Fan the fumes with your hand towards your nose SLOWLY, be sure you do not stand closer than half meter from the beaker. Do not inhale much, just to the "tip of your nose". SO2 is clearly evident when present, it is unmistakeable. And if you are able to cautiously smell it, there is enough in the solution.

Please be careful with chemistry. As Dave said, if you do not know what is happening with your experiment, and you do not know for sure what addition of this and that will cause, DO NOT DO IT. It could easily be your last addition. Chlorine is very toxic, one accidental whiff could leave you disabled for life with pulmonary problems and "dissolved" lung tissue. No jokes.

 

[orvi]

The other thing I noticed about the Instructables post is that they never heat their bleach + HCl solution or do anything else to drive off the excess chlorine after the gold is dissolved. If you have too much chlorine remaining in solution, gold will tend not to drop because it is re-oxidized and put back into solution by the chlorine. A similar thing happens with excess nitric acid in aqua regia. However, bisulfite is good at reducing chlorine to chloride so you likely reduced it when you added a large amount of it to your solution. For that reason I think this isn't your problem.

Unlike nitric acid, reaction of chlorine with sulfite/SO2 is quite quick. And chlorine is soluble in the aqueous solutions just to some extent. Heating up the solution will certainly minimize it´s content in the mixture, but one excess spoon of sulfite usually kill every last bit of Cl2 present (in my experience).

I used sulfite excessively also in my organic chemistry career, to purposefully kill traces of bromine and iodine, left in reaction mixtures. Reaction is instant. And so it is with chlorine.

So, as you said not very problematic.

 

[Malc84]

Thanks all. I managed to filter the crystals off and then added metabisulfite which then did drop the gold to the bottom of the beaker. I dried the residual black powder off and then melted it with a Map torch and a little borax however the attached is what I have ended up with! Very little gold in amongst something else. I tested the gold solution as the instructions described all the way and had a positive reaction to suggest there was gold in the solution. The only other thing I noticed was during the process of dissolving the gold foils I ended up with a white sludge at the bottom of the solution which looked like salt, I have taken this out and put it to one side. Can anyone suggest why I haven’t managed to get much gold from this process? Could it be in the sludge etc? I used 485g of ram fingers so was expecting to at least have 2-3 grams of gold.

 

[Malc84]

This is the sludge and also the crystals that were left/produced.

 

[Martijn]

Dilute until crystals are dissolved, filter, and: Cement it out. Study and start over (start small until you know what to do and what to expect)
Test the filtered solution and the cemented solution with stannous.

If you want to melt gold: only do so with clean light brown powder. if it's not clean light brown powder: do not melt. It wil not be pure gold.
Melting black stuff with ??? in it?? can do anything, because of the ??? Even gold can go up in smoke.

Powders are easy to clean, a blob of Au + ??? is not.

Trash in, trash out.

 

[kurtak]

I used 485g of ram fingers so was expecting to at least have 2-3 grams of gold.

454 grams equals 1 pound - so 485 is very close to 1 pound & for all practical purposes you can call it a pound

1 pound of close cut fingers (from RAM) will give you "about" 1.5 grams gold (if you do everything right)

Kurt

 

[kurtak]

This is the sludge and also the crystals that were left/produced.

Per the bold print - the sludge looks to me like meta stannic acid which is the result of processing boards with tin solder on them

That means the "fingers" you processed were NOT clean close cut (from the RAM)

That means you would not even get the expected 1.5 grams gold from the 485 grams of fingers

Question - did you actually cut the fingers off the RAM sticks (& cut them VERY close to the fingers) or process them as whole RAM sticks &/or not cut them very close to the fingers ?

Kurt

 

[kurtak]

I tested the gold solution as the instructions described all the way and had a positive reaction to suggest there was gold in the solution.

What color was your stannous test ?

A true positive stannous test (for gold) will range in color from purple to black (depending on how much gold is in solution)

There is such a thing as a false positive - which is often the result of using to much SMB to drop your gold

A false positive test will be brown in color --- not the purple/black you are looking for

Kurt

 

[Malc84]

The photo I sent with my final results were a bit misleading as it contained little fragments of the graphite crucible as I had difficulty in removing the so called resultant gold, when I removed it parts of the crucible broke off. The powder I was left with was a light brown colour at the start of the melting process.

Hi Kurt,
I processed RAM fingers only, but they were not as clean cut as they should have been so quite a few of the individual finger cuts included a small portion of the board with components still on them. If this is what caused the sludge then I will have to spend more time cutting them closer to the fingers and washing the boards off before proceeding to ensure they are clean. The instructions I used as listed above stated that I needed to use 6% sodium hypochlorite but I used 14-15%, would this also have caused an issue I.e. the sludge?
Below is a photo of the stannous test results, it was definitely dark purple/black as opposed to a brown.
Thank you for the clarification regarding what I should expect from the 1 pound of fingers. I also have about 2.2 lbs of RAM chips to process which I have burnt, crushed, sieved and removed all of the metallic parts using a magnet. Could I follow the same process I have for the fingers to process the chips? If not could you recommend how to process these please? Also do you know how much gold I should expect to recover from 2.2 lbs of RAM chips?

Also, what is meant by cementing it out?

I have a further 30kgs of RAM boards to process but I want to get it right before stripping everything down.

Many thanks,

Malcolm

 

[FrugalRefiner]

Also, what is meant by cementing it out?

See When In Doubt, Cement It Out.

Dave