Sciencemadness Discussion Board

fulminating gold

deadgamer1030 - 25-6-2015 at 14:34

I was attempting to recover gold from old ram cards. I used NH4NO3 and HCl to make a solution aqua regia. I put the ram in the solution to let it dissolve. This process took over night. When i went to precipitate the gold with Sodium Metabisulfite no gold precipitated out. I did some research to find out why nothing was happening. The only thing i could find online was there might be to much nitrate left in the solution and it said to neutralize it with urea. So in a small test tube i put a small amount of the solution and then added urea. Next i added the Metabisulfite and still no gold precipitated out. I have noticed a light brown to goldish precipitate at the bottom of the beaker where the solution is kept. Is this fulminating gold? If so, how to i neutralize it a retrieve the gold safely? i cannot find anything online to handle it safely. Any advice would be appreciated.

Marvin - 25-6-2015 at 15:11

It's difficult for anyone to say for sure it isn't fulminating gold but normally this substance is made by adding a strong base and letting the precipitated oxide/hydroxide steep in a solution containing ammonia. Lack of a caustic base, the acidic and reducing conditions point away. If the amount is small I'd proceed carefully with eye protection, dry a small amount of the stuff and hit it somewhere well away from the rest. Brown is not an unusual state for precipitated gold incidentally but it could be other things, copper etc.

hissingnoise - 26-6-2015 at 01:32

A solution of gold in aqua regia with NH4 will contain fulminating gold!

It is precipitated by adding K2CO3 sol.!

I'd be wary of attempting to reclaim the metal due to FG's reputation . . .

deltaH - 26-6-2015 at 02:11

I point you to an excellent review of fulminating gold:
http://publik.tuwien.ac.at/files/PubDat_170506.pdf

From that paper:
Quote:
For safe disposal of fulminating gold, dissolve it in
hydrochloric acid (concentrations > 0.2 M). Dissolution
may consume some time, thus it is advisable to let the
suspension stand for at least 24 hours. Thereafter, only a
little residue might remain undissolved on the bottom of
the beaker. It can be wiped out with a paper towel without
a hazard.


Be safe and not the general safety advice in that paper:
Quote:

• If possible, use secondary amines or primary amines with
a large alkyl group (e.g. mono-t-butyl amine) instead of
ammonia to avoid the formation of explosive products.

• Avoid an excess of ammonia (which increases the
product’s sensitivity) in the course of your reaction. Use
as little as possible.

• In your reactions with gold(III) compounds, be aware that
some chemicals may release ammonia, e.g. ammonium
carbonate or urea at elevated temperature.

• Without a major excess of ammonia, the addition of
significant amounts of sodium or potassium cyanide to
the slightly basics solution can prevent the precipitation
of fulminating gold [35, 43]. Be aware of the formation of
very toxic hydrogen cyanide gas from acidic solutions!

• Do not wash the precipitate, neither with water, nor (even
worse) with ammonia solutions or bases. Both leads to
the formation of even more sensitive and explosive
products.

• If you accidentally obtain a precipitate from a reaction of
gold(III) compounds and ammonia, do not dry it, but
keep it moist. Only the dry product is explosive.

• Precipitation in presence of excess amounts of NH4+and/ or Cl–(e.g. NH4
Cl or NH4NO3) leads to a less (in case of Cl–) or not explosive (in case of NH4+) product.

• Do not synthesize or handle larger quantities than 500
mg of fulminating gold.

• Use safety equipment when handling fulminating gold,
such as: safety goggles, face shield, leather coat,
earthening (person and equipment), KevlarTM gloves and
wrist protectors and ear plugs. In general, avoid the use
of glass or metal equipment (e.g. spatula) because of the
possible formation of shards or shrapnels in case of an
explosion. Use plastic beakers and spatula instead. Only
for the drying of wet, freshly precipitated fulminating
gold in the desiccator, the use of a glass beaker has
turned out as practicable, because fulminating gold
tends to adsorb on the bottom of a polypropylene beaker
in the course of drying, from where it can be removed
only by hazardous scratching.

• Avoid friction to the dry product. Remember its high
friction sensitivity. Act in a concentrated way and handle
the product with care and precaution.



[Edited on 26-6-2015 by deltaH]

aga - 26-6-2015 at 08:06

Jeez.

So a shortcut to get to aqua regia can wind up with an explosive instead of $.

Note to self: go with the nitric & hydrochloric acid method instead.

deadgamer1030 - 26-6-2015 at 08:18

Next time i try this recovery, I will convert the NH4NO3 to NaNO3 with NaOH. Thanks for the help.

deadgamer1030 - 26-6-2015 at 10:02

The solution also tests negative with SnCl4.

[Edited on 26-6-2015 by deadgamer1030]

deltaH - 26-6-2015 at 10:26

Try dissolving it in 1M HCl overnight, it's simple enough. Gold obviously won't dissolve in HCl. Hope you come right!

pneumatician - 26-6-2015 at 14:53

before play with chem read some data here and there, do not just repeat what parrots say

from a ebay seller ( minerals-water.ltd):
Lately, sodium sulfate has been found effective in dissolving very finely electroplated micrometre gold that is found in gold electroplated hardware on electronic products such as pins, and other connectors and switches. It is safer and cheaper than other reagents used for gold recovery, with little concern for adverse reactions or health effects.

de res. :D

aga - 26-6-2015 at 15:00

I thought i had heard that somewhere, and prepared some sodium sulphate today (by-product of making GAA)

Do you have any further details other than just to dissolve Gold in Na2SO4 ?

How to get the dissolved Gold out of solution would a useful, for example.

[Edited on 26-6-2015 by aga]

cyanureeves - 26-6-2015 at 18:13

unless it's alot of gold i'd keep the precipitate in water until i could use it for a plating solution or whatever.this stuff ruined my day one time and left an abrasion in my eye caused by blast pressure.i let it dry and tried to scrape it out of the bottom of the glass flask it was in.crazy thing is i was warned in this very forum about precipitating with ammonia but thought it was just alarmists talking.it doesnt take much gold to make this explosive either.my batch came from just one old computer i believe or maybe rolled gold,i forget which but recall it wasnt much.my sight is more important than any gold now.

Marvin - 28-6-2015 at 16:11

Does minerals-water have more details for that sodium sulphate process or is it just the old unreferenced claim from wikipedia?

vmelkon - 28-6-2015 at 18:33

Quote: Originally posted by Marvin  
Does minerals-water have more details for that sodium sulphate process or is it just the old unreferenced claim from wikipedia?


I think that was a joke or some kind of silly error by some e-bay dude.

woelen - 29-6-2015 at 02:13

Sodium sulfate cannot be used for precipitating gold. Sodium sulfite can be used for that purpose. There only is one letter difference in the name of the chemical, probably that leads to the confusion.

If precipitating gold, keep pH sufficiently low. This keeps nearly all other metals in solution and prevents precipitation of dangerous unstable compounds.

Marvin - 29-6-2015 at 05:13

Allegedly sodium sulphate is for dissolving gold, not precipitating. It's exists as an unreferenced contribution from an unregistered user on wikipedia in 2007. Minimally it appears to be out of context.

woelen - 29-6-2015 at 05:44

How could sodium sulfate dissolve gold? Sodium sulfate is a really dull chemical, even table salt is more reactive.

Dan Vizine - 29-6-2015 at 14:58

Perhaps they meant sodium hydrogen sulfate? Seems to me I've heard of this somewhere? Sounds like a high temp process?

The solubility of noble metals is a funny thing, though. While you can't dissolve gold in HCL, gold alloys will dissolve. Electrum dissolves in HCl /NaCl. But that isn't a focus here, the gold is present as gold, not an alloy.

Economics is the real killjoy. A currently heard statistic is that 300 to 400 lbs of computers will give an ounce of gold. How many hours are you going to invest in pulling them apart, disposing of the carcasses, processing the boards, purifying the resultant mess? How many dollars will it cost for chemicals, equipment? I heard this really only becomes worthwhile at ton levels. It may be interesting, but it's no "get-rich-now scheme".

Oops, just noticed you said RAM cards. Higher gold/lb ratio, but do you really have the vast number you'd need to make it worthwhile?



[Edited on 29-6-2015 by Dan Vizine]

pneumatician - 30-6-2015 at 09:06

ironically I say "do not just repeat what parrots say" and making a low search 99% of people say the exact words:
"Lately, sodium sulfate has been found effective in dissolving very finely electroplated micrometre gold that is found in gold electroplated hardware..." LOL!!!! :D :D :D :D

well, and now seriously this appeard to be a "secret" process or patent and is useless the claims of all this people unless you know the procedure.

but sodium sulfate DISSOLVE GOLD, PERIOD.

I don't post the procedure, I thing people can find by himself, if nobody found the process, perhaps...

really in all the thousands of fat books of chem floating around nobody say anything about this????

Warning, this disquisition, of course, is not suitable for people brainwashed.

------------
Do not believe anything
because it is said by an authority,
or if it is said to come from angels,
or from gods,
or from an inspired source.
Believe it only if you have explored it
in your own heart
and mind and body
and found it to be true.
Work out your own path,
through diligence.

Gautama Buddha
----------

AJKOER - 30-6-2015 at 11:28

OK, for guys whose true avocation is gold mining, I guess we can accept an omission of a few letters. Here is Wikipedia on Gold extraction via Sodium thiosulfate (link: https://en.m.wikipedia.org/?title=Sodium_thiosulfate ):

"Sodium thiosulfate is a component of an alternative lixiviant to cyanide for extraction of gold.[6] However, it forms a strong soluble complex with gold(I) ions, [Au(S2O3)2]3−. The advantage of this approach is that thiosulfate is essentially not toxic and that ore types that are refractory to gold cyanidation (e.g. carbonaceous or Carlin-type ores) can be leached by thiosulfate. Some problems with this alternative process include the high consumption of thiosulfate, and the lack of a suitable recovery technique, since [Au(S2O3)2]3− does not adsorb to activated carbon, which is the standard technique used in gold cyanidation to separate the gold complex from the ore slurry."

What is curious is that it can be prepared by heating an aqueous solution of sodium sulfite with sulfur. Also, on heating the dry salt to 300 °C, it decomposes to sodium sulfate and sodium polysulfide:

4 Na2S2O3 → 3 Na2SO4 + Na2S5

There exists also soiled based sulfur reducing bacteria that attacks Na2SO4, so I would not be too shock if there is actually a connection between Gold extraction and a Sulfur source from any of the three cited compounds, Na2S2O3, Na2SO3 and Na2SO4.

The above problems cited by Wikipedia on the thiosulfate route, however, leaves doubt in my mind as to whether it constitutes a good alternative lixiviant.

[Edited on 30-6-2015 by AJKOER]