Refining Gold From Circuit Boards & Electronic Scrap
with Muriatic & SubZero
(nitric acid Substitute)
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Refining Precious Metals Page
The
acid used in this process is muriatic (also known as hydrochloric) acid.
This acid is corrosive (see warning label on your bottle).
For this reason, this kind of refining is best done outdoors, away from
anything that may be damaged by exposure to these fumes.
Having described it's hazards,
it must be pointed out that, like most industrial processes, refining gold in
acid is quite safe when performed under controlled conditions.
In addition, the results of doing your own refining can be quite sweet.
Based upon feedback we've gotten from several hundred users, we estimate
that the return of gold, when you refine the material yourself, is 10 times the
return when sent in to a commercial refining company.
To refine gold with the SubZero Aqua Regia , you will need the following
additional items:
·
protective clothing--minimum requirement: goggles and rubber gloves.
·
muriatic or hydrochloric acid.
·
baking soda (sodium bicarbonate) to neutralize the acid when finished.
·
tap water and distilled water.
containers
for the boards.
Before refining:
Cut off those portions of the board that have gold.
Discard the rest. Chips, which have gold inside as well as outside, must be
broken open. On a small scale, one tap with a hammer should suffice.
With lots of chips, you might want to use a cement mixer.
In a glass or plastic container (a 5 gallon, clean white
bucket will work well), add 1 lb SubZero to
½ gallon of muriatic or hydrochloric acid.
Do not use a metal
container.
Not all the SubZero will
dissolve. This is normal.
Do not discard the undissolved SubZero-
The undissolved SubZero is required to be in the solution
for the gold to complete its dissolution.
Dissolving the gold:
The acid should be at room
temperature. Place your boards in a
plastic mesh, or plastic wire basket or a plastic mesh bag.
The acid has to pass through the basket or bag, so make sure it is either
plastic mesh or plastic wire.
Add the
basket or bag, with your boards, to the acid solution. The metal
will begin to fizz and give off an invisible or slightly brown fume. You can
cover the container, but do not seal it tightly because you don't want a built
up of gas pressure. You can
speed up the process by heating your solution, but this creates added hazard-
hot acid fumes more rapidly and is more corrosive.
At room temperature, dissolving time is usually between ½ hour
and 2 hours. Check the boards to make sure all the gold has been removed and
dissolved into the aqua regia acid.
Remove
the basket from the acid, taking care not to drip acid anywhere. The aqua
regia is not used up yet, so you can use the same acid to dissolve the gold off
more boards. You can continue to use this acid, several times, to dissolve
the metal off additional boards until it is no longer effective.
The acidy boards should be rinsed (with water) in another bucket.
Any brown particles are likely to be gold and should be recovered and put
into a future refining bath. If you
believe that some solid bits have fallen into the solution during dissolving,
then (after the acid is no longer effective in dissolving any more metal),
you should pour the solution into a different bucket, leaving the solids
behind. Any solids left in the
solution will contaminate the pure gold you are about to precipitate
Adjusting the pH & Precipitating the pure gold:
When the aqua regia is no longer effective (no longer
dissolves the gold on the boards), it is time to recover the pure gold from the
solution.
The
acid will be a dark, emerald green color and should be clear, like Coca Cola,
not murky or muddy looking (nothing floating inside the dark waters).
If the acid is murky, it may contain particles and should be decanted
into another 5 gallon bucket or it should be filtered.
Now add a pinch of urea to the dark acid solution.
If it fizzes, add additional urea until it no longer fizzes.
When there is no longer any fizzing, it is time to precipitate your pure
gold.
Measure out all the precipitant that you need (add 1½
tablespoons of Storm Precipitant for every ounce of dissolved metal (dissolved
metal content, not just dissolved gold content) and put in the bottom of a clean
white bucket. At your acid to the
bucket containing the precipitant.
Immediately, the acid will change to a muddy brown appearance as brown particles
of gold form in the acid. This
brown "mud" is, despite its appearance, pure gold.
Once
precipitation is complete, test the acid for the presence of dissolved gold with
Precious Metal Detection Liquid.
Testing to make
sure no dissolved gold is discarded:
Precious metal detection liquid will detect the presence of dissolved gold, down
to 4 parts of gold per million parts of acid, detecting the presence of about
1/1,000th of 1 gram of dissolved gold.
Testing for the presence of dissolved gold is absolutely necessary to
insure that no dissolved gold is thrown away with the waste acid.
To
test, first immerse the end of the stirring rod in the acid.
Remove it and touch that end to a paper towel to make a wet spot.
Put a drop of gold detection liquid on the wet spot on the paper towel.
If any gold is still dissolved in the acid, the wet spot will turn a
purple-black or a purple-brown. If
you see this color change then give the precipitant more time to work and/or add
more precipitant.
Rinsing the pure
gold:
The
acid should now be a clear, amber or a green color with a brown mud at the
bottom. Pour off the acid into
another container. If you have a
filter, you can use it. Do not pour
off any of the mud. The mud is pure
gold.
When all the acid is poured off,
add 2-3 gallons of tap water to the mud.
Be sure to pour off all of the acid before adding water.
Stir the water and then let the mud settle.
Pour off the water into the container with the acid.
If you have a filter, you can use it-
however, it is generally easier to decant the water off the top rather
than use a filter. Be careful not to pour off any particles of brown with the
water. Repeat this rinsing 2-3 more times and then test the purity.
Testing to insure
purity:
Test
with aqua ammonia to insure high purity of your gold. Tilt your bucket so that the small amount of water retained
in the gold mud runs off and form a very small puddle in the corner of your
bucket. Place a drop of aqua
ammonia test liquid in the puddle.
If you see any change in color to blue, even a very pale blue, rinse and test
again.
Give the mud a last rinse, this time with distilled water.
Drying and
melting:
Rinse
the mud into a beaker that is made to be heated or into glass coffee pot.
Put the beaker or pot on a hot plate to dry the mud. Do not preheat the hot plate or thermal shock may cause the
beaker to break.
Melt the dried mud (now a powder).
If using a torch, first wrap the powder in tissue paper and then soak that in
alcohol. Also, use a Burno
crucible. This will keep your gold
from being blown away by the gas pressure from the torch.
The gold will again take on the appearance of metal.
If you've followed the instructions carefully, the gold will be 99.95 %
pure with virtually no losses.
Platinum-
Computer
Scrap- Very few boards have
platinum. Typically, platinum (and
other platinum group metals, like palladium) are found on the surface of the
hard drive platter (the inside is aluminum).
To dissolve the aluminum, first make cut marks across the disks and then
put in a saturated solution of cold water and lye.
Lye is very corrosive, so wear protective gear.
As the solution comes in
contact with the aluminum, the solution will become very hot and the aluminum
will dissolve. Discard the solution
and recover and rinse the platinum.
The platinum will not be pure. To
make pure and to separate one platinum metal from another, you will need the
Simplicity Refining System.
Catalytic
Converters-
Follow the normal procedure for refining gold, but heat the SubZero aqua regia
to simmering. Remove and replace the catalytic converters after the platinum is
dissolved off the surface. Precipitate
the platinum from solution with zinc powder or aluminum foil.
The precipitated metal