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Author Topic: Ways to dissolve Gold  (Read 30472 times)

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science2000

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Ways to dissolve Gold
« on: October 25, 2005, 04:31:43 PM »

Gold seems like an interesting element to get in solution and observe, but I lack aqua regia to dissolve it in, and I refuse using sodium cyanide. Does anyone know some alternate ways to dissolve gold?

Okay, I have one idea but I need to know if it's right. If I put some small flakes of gold I have (panned some), in a small vial, and added Hydrochloric acid and commercal hydrogen peroxide, and it would produce small bubbles of Chlorine that would form on the gold. The amount of Chlorine being produced shouldn't be very dangerous with literally a fifth of a small vial of this solution. Gold, like most metals, would react directly with a halogen, right. And this reaction would yield Auric Chloride.

Another idea, similar to the above, I would place some gold in a Tincture of Iodine solution. Iodine isn't as reactive, but it's a halogen.

« Last Edit: October 25, 2005, 04:35:25 PM by science2000 »
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AWK

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Re:Ways to dissolve Gold
« Reply #1 on: October 25, 2005, 10:52:27 PM »

You can use household bleach and HCl (add dropwise under hood, or at least outdoors). Do it in glass, not in stainless steel utensils.
« Last Edit: October 25, 2005, 10:55:44 PM by AWK »
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jdurg

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Re:Ways to dissolve Gold
« Reply #2 on: October 26, 2005, 10:02:38 AM »

Gold's reaction with the halogens, however, is VERY slow and takes a lot of time to complete.
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science2000

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Re:Ways to dissolve Gold
« Reply #3 on: October 26, 2005, 02:25:25 PM »

The surface area is good with this small trifling amount of gold. You'd figure a few days, or maybe a few weeks? Chlorine is somewhat soluble and bubbles don't necessarily have to form on the metal 24-7, right??
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AWK

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Re:Ways to dissolve Gold
« Reply #4 on: October 26, 2005, 08:47:51 PM »

Gold's reaction with the halogens, however, is VERY slow and takes a lot of time to complete.

Gold fillings dissolve in a few hours when solution is mixed
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jdurg

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Re:Ways to dissolve Gold
« Reply #5 on: October 28, 2005, 03:41:16 AM »

Gold fillings dissolve in a few hours when solution is mixed

Yes, because gold fillings are a finely dispersed solution of gold inside another metal.  The cohesive forces between gold and itself aren't all that strong due to the small particle sizes.  You can speed up your dissolution by taking your gold nuggets/scrap and dissolving it in a lot of mercury.  (You want a lot of mercury so that the solution doesn't solidify).  In a WELL ventillated area, you would then distill the mercury out in a distillation apparatus which would leave you with a VERY fine powder of gold dust and other metal dust.  This should dissolve almost instantly due to the incredibly small particle size.
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Borek

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Re:Ways to dissolve Gold
« Reply #6 on: October 28, 2005, 04:33:29 AM »

This should dissolve almost instantly due to the incredibly small particle size.

The smaller the fillings, the larger surface area per mass unit.
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science2000

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Re:Ways to dissolve Gold
« Reply #7 on: October 28, 2005, 07:05:23 PM »

I recently pulled some small gold pins of an old 486 processor. I'd like to use these. Are these solid gold, or gold plated? Because after putting the pins in a vinegar/peroxide solution, no copper was oxidized and dissolved. Larger pins on the motherboard are always loaded with copper under the gold plating, which turns up easily in the solution as a blue coloring.

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science2000

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Re:Ways to dissolve Gold
« Reply #8 on: October 29, 2005, 11:43:35 AM »

I'm getting a yellow-gold coloring in the solution, is this the color aqueous gold ions are supposed to make? It sounds obvious, but I'd like to be sure.
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Borek

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Re:Ways to dissolve Gold
« Reply #9 on: October 29, 2005, 11:54:14 AM »

Nothing obvious here. Using this logic, copper salts should be red, not blue.
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science2000

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Re:Ways to dissolve Gold
« Reply #10 on: October 29, 2005, 08:26:55 PM »

Now the solution is a kinda yellow-green color. It forms a brownish precipitate when I add ammonia to a drop. Then it forms a reddish solution when I add acetic acid to that. Note the acetate isn't very soluable, as one would expect from gold acetate. Weird, huh? I'm thinking it's a nickel-palladium-gold alloy like I read about. Nickel would give a greenish color to a solution.
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Ian Donaldson

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Re:Ways to dissolve Gold
« Reply #11 on: October 30, 2005, 12:29:59 PM »

The elizabethans made Aqua Fortis - ie nitric acid by heating saltpeter with copperas - that is heating potassium nitrate with ferrous sulfate.  To make Aqua Regia you simply add HCL - formed from heating oil of vitriol with common salt.
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woelen

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Re:Ways to dissolve Gold
« Reply #12 on: November 02, 2005, 12:20:14 AM »

Now the solution is a kinda yellow-green color. It forms a brownish precipitate when I add ammonia to a drop. Then it forms a reddish solution when I add acetic acid to that. Note the acetate isn't very soluable, as one would expect from gold acetate. Weird, huh? I'm thinking it's a nickel-palladium-gold alloy like I read about. Nickel would give a greenish color to a solution.
A solution of gold in HCl is beautifully orange/yellow. The green color you see is most likely due to copper impurity, but it might also be nickel (palladium I think is quite unrealistic, I simply cannot believe that the legs of a CPU are filled with palladium, that would make it really costly). Copper ions have a green color in aqueous HCl, not blue. So, the yellow/green color can perfectly be understood. Nickel ions also are green.

You can easily separate the two metals. Add a mild reductor to your liquid (I think vitamin C in acidic environment will do already) and then wait, till all gold has settled as metal. Decant the liquid, rinse and then redissolve the metal deposit. Now you only have fairly pure gold metal in solution.
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science2000

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Re:Ways to dissolve Gold
« Reply #13 on: November 02, 2005, 08:29:18 AM »

The next time I added HCl and H2O2 to the CPU pins, it was only a yellow solution. But now I want to crystallize a salt with gold in it, I've read somewhere it's salts have very attractive crystals, but gold chloride is very hygroscopic. Any suggestions?
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