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There's Gold in Them Thar Computers (18 pics)

Posted by sym in Pictures   27 Aug 2010   / 125835 views

Gold is used in many different types of electronic equipment, especially computers. With the price of gold being at an all time high, there are now numerous companies who are recovering the infinitesimally small amounts of gold. Most of the gold is found in the motherboards. 


Here’s a process of gold extraction from motherboards. This process is dangerous, therefore don’t try to reproduce it at home. 

Gold is found in numerous places on a motherboard: IDE connectors, PCI Express slot, PCI, AGP, ISA, and other ports, jumper pins, the processor socket, and DIMM (SIMM on older motherboards) slots.

All of these connectors are often covered with a fine layer of gold a few microns thick, deposited by flashing or plating.

So, the first stage of the experiment is to recover all these pins and connectors. We need pliers and cutters, flat and Philips screwdrivers, and liberal amounts of elbow grease...

You need a lot of pins to conduct this experiment, and that's exactly what our donor boards provided...

...along with some equipment and chemicals.

To recover the few micrograms of gold deposited on the pins, we’re going to use an electrolytic cell. The bath consists of a 95% solution of sulfuric acid. The cathode is lead and the anode is copper. The pins are placed in the copper anode, which we’ve formed into a basket shape.

By running an electrical current through the cell, using an ordinary battery charger, the copper in the anode (and in the pins) dissolves and is deposited on the lead cathode. The gold, detached from the copper, forms a sediment at the bottom of the cell. Also note that the temperature of the bath increases significantly during this process.

Once all of the gold has detached from the pins, the bath is allowed to settle. Then, we recover as much of the sulfuric acid as possible, before diluting what remains in the bottom of the electrolytic cell.

Be careful to always pour acid into water, and not the other way around! If you do it wrong, the first drops of water that touch the surface of the sulfuric acid will immediately be vaporized and could cause acid splashes.

We end up with a diluted solution of sulfuric acid, various metals (including gold), and waste that then needs to be filtered. Why not just filter the solution directly, without diluting it? Because paper filters don't stand up well to strongly concentrated sulfuric acid. That's why.

What remains in the filter is a mixture of various metals and impurities. We now dissolve everything in a mixture of hydrochloric acid at 35% and chlorine bleach (sodium hypochlorite) at 5%, in a proportion of 2 to 1.


2 HCl + NaClO -> Cl2 + NaCl + H2O


Careful! The reaction is highly exothermic and produces chlorine, a highly dangerous gas. Chlorine gas was used as a chemical weapon during the first World War, under the name bertholite.

In fact, the chlorine produced by mixing hydrochloric acid and chlorine bleach is what will dissolve the gold to form gold(III) chloride.

2 Au + 3 Cl2 -> 2 AuCl3

Now, all we need to do is filter everything once again. The filter will retain all the impurities, leaving only a gold(III) chloride solution.

To recover the metallic gold, we now need to precipitate the gold that’s in solution. For that, we use powdered sodium metabisulfite. In the presence of water, the sodium metabisulfite produces sodium bisulfite.

Na2S2O5 + H2O --> 2 NaHSO3

This sodium bisulfite is what will allow the gold to precipitate.

3 NaHSO3 + 2 AuCl3 + 3 H2O --> 3 NaHSO4 + 6 HCl + 2 Au

We let the solution settle, then we recover the brown powder collected at the bottom of the beaker. We have to be careful not to lose any--that’s metallic gold!

Now, all we need to do is to melt the powder in a crucible.

The melting point of gold is around 1064° C (1947.52 °F), so an oxy-butane torch will do the job.

And here's the result!


Comments (19):

Juanpa 6 year s ago MARK AS SPAM
nice, it reminds me of Breaking Bad with the home lab
a question, does it worth? the gold can afford the cost of the chemicals and leave a gaining?
Wizard 6 year s ago MARK AS SPAM
Cool, I'd di it right now but I have all the ingredients except for that cool red funnel. LOL
fahkinright 6 year s ago MARK AS SPAM
doesn't seem worth the effort???
Mattus 6 year s ago MARK AS SPAM
very cool
but would cost more than it makes if you dont already have the stuff??
owner 6 year s ago MARK AS SPAM
or you can just buy gold
Zeke678 6 year s ago MARK AS SPAM
pretty cool, but, probably only worth the effort and chemical costs on large scale production, i.e. with computer graveyards.
SuperMilow 6 year s ago MARK AS SPAM
CrownRoyalty is truly the best kind of royalty their is!
NOPE 6 year s ago MARK AS SPAM
o boy a gold BB totally worth the effort.
cool 6 year s ago MARK AS SPAM
I work at the local chip factory at the metal deposit..
That means I do the complete opposite!!

Or not 6 year s ago MARK AS SPAM
That BB isn't worth the stamp it would take to mail it to a buyer. Even a pile of outdated mobos probably has a higher net worth, not to mention the cost of the chemicals, and your time.
severe_009 6 year s ago MARK AS SPAM
Hmmmmm interesting,
Challenge breeds excellence...
samthesham 6 year s ago MARK AS SPAM
Very interesting!
goldsmith 6 year s ago MARK AS SPAM
Seems overly complex to me. Why bother with the electrolytic cell, when the copper would dissolve in sulphuric acid all on it's own without the current, and then also without wasting an anode and cathode. Or better, use nitric. That will dissolve everything other than the gold and any platinum group metals directly. So long as the gold that was there was already pure (and electroplated gold is essentially pure), simply removing the other metals is all that's required. Any silver present (some types of switch contacts) would also dissolve, but could be recovered from the nitric acid by adding table salt solution to precipitate silver chloride. From the original nitric bath, what remains in the beaker undissolved would be non-metallics, gold, and any platinum group metals. But PGMs aren't common in electronics, so essentially, you'd have just gold there, without the other steps. Certainly, gold recovered this way would be pure enough for use in jewelry, or to sell to a refiner. Only if you needed extra high purity gold would you need to do more than this. In normal gold refining, one is extracting the gold from more complex alloys, so often more extensive means are needed. But electronics are not like that. The gold that's there is pretty much pure. Note that there are other sources of gold in electronics. Your method doesn't get the gold plated onto the boards themselves, nor the tiny gold connecting wires inside the IC chips. For that, you'd need to grind up the whole mess. Usually, the method then is soaking in dilute cyanide to dissolve the gold, then removing the gold from solution electrolytically. But that's obviously not small scale kitchen chemistry, and if you think acids are nasty, cyanides are more so, at least for non-professionals.
benchn 6 year s ago MARK AS SPAM
price of all those motherboards and circuits, chemicals and utilities to make these? a fuckload i imagine... is it really worth it?
PYTHON2374                    show commment
Dreth 6 year s ago MARK AS SPAM
At last,a post here that sparks intelligent conversation instead of the general mumbling banter of an idiot's idea of "sucky posts".
Calixaren 6 year s ago MARK AS SPAM
You mentioned at the start that this process is dangerous and should not be repeated at home. Funny enough, you are wearing safety goggles and protective gloves - what about your lungs? Got a fume cupboard to protect you from the toxic gases (chlorine)?

By the way, professionals do filtration of concentrated acids with filters made from sintered glass, not paper filters. But then you need a vacuum pump and other equipment to do it appropriate.

Not very clever to start a process without adequate equipment.
4down2 6 year s ago MARK AS SPAM
A BeBe pellet..can,t shoot a Vampire with it !
MetalMulholland 4 year s ago MARK AS SPAM
Thank you for the info.

And all of you people who think it is not worth your time... your right its not you would probably just hurt yourself anyways. So keep throwing away your old electronics I'm sure someone is thanking you for it.

@or not: not everything is sold on ebay you effin nerd get outside and explore.