Sciencemadness Discussion Board

Gold or not Gold, thats the question

RU_KLO - 27-2-2023 at 06:25

Im trying to get some Gold for making Gold salts/solution for future qualitative sample of gold tests.

I salvaged some golden pins from a ZIF processor socket. they also contained a lot of solder
Put them in HCl + H2O2 (read a post somewhere that its possible to use that combination for dissolving gold)
The solution Ive got was blue. (when I tested a sample of this solution by adding some NaOH it precipitated as a "smurf" blue precipitate).

Then I read that for precipitating gold, metabisulfite or bisulfite is used. Did not have, but instead used Sodium sulfite that I had. Some acid smell (cannot confirm if HCl or H2SO4 smell it was)

1) Can Sodium sulfite used for precipitation of gold?

the solution turned first brown then black. rapidly settled on the bottom a black precipitate.

As I read, the precipitate should be brown (not black). My first thinking is that that was not gold, but something else.

tested a sample with HCl, but did not dissolve, even by boiling the solution. Tested with concentrated HNO3 and it dissolved giving a "grey/green" milky solution. (some NO2 vapors were produced, not much)

So probably the precipitate was Copper Oxide.

2) Is my thinking OK? (if not what did I get)

After decanting, a "blue/green" liquid stay on top and a "grey" in the middle and a small black layer on the bottom.
here is a picture:

Do i have gold? How can I extract it?

Cathoderay - 27-2-2023 at 07:56

I don't know a lot about gold recovery. I do know about electrical equipment.
Do you realizes the coating of gold is extremely thin?
There is probably 1000 times more other metals there than gold.
Many electrical contacts are made from phosphor bronze (a copper alloy) because the contacts need to be springy.

All the metals present have to be evaluated for there reaction to the chemicals.
Temperature and pH could be important.
Where are you "reading" about the various reactions? The context might be important.

RU_KLO - 27-2-2023 at 11:03

mainly from this forum. (H2O2 + HCL)

The rest is trial and error learning.

Rainwater - 27-2-2023 at 11:14

Your best bet now is to use thermal decomposition to start over
What you want to do is use gold's chemical resistants to remove everything but the gold.
By taking gold into solution from the start, it becomes more difficult to refine.

1)yes. But the endpoint is harder to spot. You need more than if you used smb.
Brown/black. Yes No.... the particles are so small the color is dark. Not something to worry about.

2) your precipitate is mixed metal oxides, probably some iron( will turn red with air) nickel, tin, and lead.

When I was in your position, i fired everything back molten and start over.
Plenty of step by step procedures on youtube and here and
The standard amateur route is inquart then bathe in hot nitric until no more orange/brown smoke.
Decant and repeat until a clear solution is obtained and no more nitric is consumed

Herr Haber - 27-2-2023 at 12:13

An idea I found either here or on YT about inquarting:

If you have gold and are also refining silver from silverware use it instead of copper. Two birds, one stone.

I highly recommend Sreetips on Youtube. If it has to do with precious metal recovery he probably has a video or ten with what you are looking for.
(And he has a sooting voice)

Cathoderay - 27-2-2023 at 16:55

NileRed has a series of two videos about recovering gold from electronic parts.
Note that PCB probably have a different type of base metal than the socket pins.
The HCL + H2O2 is used to dissolve the base metal not the gold.

Also chemistry is fairly exacting, using reagents other than that recommended just because you don't have what is called for is like eating soup with a fork because you don't have a spoon. It probably will not work well.
Doing a chemical process is difficult enough when you have the right chemicals and equipment.
Of course if you just want to waste chemicals then go ahead.

Texium - 27-2-2023 at 17:06

Quote: Originally posted by RU_KLO  
mainly from this forum. (H2O2 + HCL)
Please link the thread then.

RU_KLO - 28-2-2023 at 04:59

mainly from this forum. (H2O2 + HCL)

Cathoderay - 28-2-2023 at 18:54

I take it that your goal is to obtain a pure gold salt rather than gold metal.
You also are not interested at this point in selling the gold.

That may suggest that you might not want to use methods that are used for gold recycling like from jewelry (high percentage of gold in source). You also might not want to used processes used for ore refining (lots of non-metals in source).

Just what weight of the pins do you have?

RU_KLO - 1-3-2023 at 03:58

there was not much (1 gr at least), but thought that the gold content was high.
As stated, I do no need gold for selling or making a ring, but for salt/solution as pure as possible (with the less contamination as possible) to not interfere with qualitative tests.
I will not continue with current solution and wait till I get more pins/pcb, etc to proceed again.

My goal is 100ml 0.1 molar Au3+ solution, so aprox 2grs of gold is needed. for me its a lot (after seeing checking some YT videos a lot of pins/pcb are needed)

Maybe a 0.01 molar can also be used.

Sulaiman - 1-3-2023 at 08:11

2g of gold requires A LOT of scrap
(or some not easily/cheaply available 'high grade' scrap)
Recovering even 0.2g would create quite a lot of waste.
Cheaper, quicker and easier to buy gold!,
if its just the salt that you want, and not the experience.

Rainwater - 1-3-2023 at 08:46

196.97g/mol × 0.1M × 0.1L = 1.969g Au × $58usd/g × 125% for labor $150 + s&h would be reasonable for the salt you want.
Thats a different molarity that you talked about, should work tho

[Edited on 1-3-2023 by Rainwater]

Cathoderay - 1-3-2023 at 10:00

I don't know were you are located, but you might be able to buy a small piece of gold (99.9% pure) and then dissolve it in aqua regia. That would give chlorauric acid HAuCl4 in an acid solution. I don't know if it would be possible to neutralize the acid and I don't think you could crystalize it.

RU_KLO - 3-3-2023 at 04:24

yes, thats the way Ill try, to buy 1gr of 99.9% gold and make a solution of it.

Thanks for the support.

Cathoderay - 3-3-2023 at 10:46

Do check around, from a brief search I made, the price can vary a lot.
A "Gold Broker" may charge a high markup for his service, what is know as a "Pawn Shop" in the US might have nearer the base price of the metal. Having the metal "certified" or assayed will increase the cost.

pneumatician - 2-5-2023 at 10:04

put household hcl wait and "fish" the gold leaf :-)


he who is not satisfied is because he does not want to

[Edited on 2-5-2023 by pneumatician]

Sulaiman - 3-5-2023 at 02:14

a better choice would be nitric acid.

Rainwater - 3-5-2023 at 09:53

A cheaper choice would be reverse electroplating with saltwater(NaCl). Plated part goes to (+)

Osmiridium - 4-5-2023 at 15:55

Some oxidizing agent is needed, HCl alone will not dissolve gold.

HCl/Cl2 also works for dissolving gold and platinum.

Sulaiman - 4-5-2023 at 21:03

Quote: Originally posted by Osmiridium  
Some oxidizing agent is needed, HCl alone will not dissolve gold.

The method currently being discussed is where base metals are dissolved away leaving gold as a solid remaining,
it is an alternative to dissolving everything including the gold (eg using aqua regia)
Both methods work.

draculic acid69 - 6-5-2023 at 04:46

Quote: Originally posted by Cathoderay  
Do check around, from a brief search I made, the price can vary a lot.
A "Gold Broker" may charge a high markup for his service, what is know as a "Pawn Shop" in the US might have nearer the base price of the metal. Having the metal "certified" or assayed will increase the cost.

I've always been able to go to a cash 4gold place or pawnbrokers and most have xrf testing facilities. They tell exactly what is in a chunk of metal and it's always free