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How to Refine Gold from Computer Parts

This is one of methode to dissolve gold from old computer parts. Use it only on computer parts, such as CPUs, ceramic chips, “fingers”, etc..., after removing them from the circuit boards. DO NOT try to use this formula on circuit boards.

A variation of this formula, substituting Sulfuric Acid for the Hydrochloric Acid, will work for pins, but you should wait until you have success first with other simple items before trying to refine pins.

Formula to Make Aqua Regia. This quantity of ingredients is for about 200 grams of mixed metals, gold, copper, etc.

1 quart of Muriatic Acid (31%)         
1/2 pound Sodium Nitrate 16-00-00
Distilled water (tap water is usually O.K).

Additional ingredients for precipitating out the gold:
1. Urea
(The Urea you get should be nice clean white pellets a little larger than BBs. Some people are getting dirty Urea, with other stuff mixed in, it may cause problems.)
2. Sodium Metabisulfite

2 Five gallon buckets
Cloth for filtering

Please note: The instructions call for distilled water. I never use distilled water. I only call for distilled water to cover the possibility that your tap water could have some weird substance in it that may cause some problems. MOST likely if will be just fine to use whatever water is available to you. You could always do your learning with distilled water if you like, and then once you’re confident of your abilities, switch to tap water, and see if there’s really any difference.

Place the metals you want to dissolve in the first bucket. Dissolve 1/2 pound of Sodium Nitrate (Nitrate of Soda 16-00-00) in 16 oz. of HOT distilled water, and pour it over the metals. Then add the 1 quart of Muriatic Acid (Hydrochloric Acid). This is the method I use.

An alternate method is to dissolve 1/2 pound of Sodium Nitrate (Nitrate of Soda 16-00-00) in 16 oz. of HOT distilled water and then add the quart of Hydrochloric Acid to the Sodium Nitrate solution. Usually (but not always) a salt will form rather quickly and settle to the bottom. You then pour off the Aqua Regia, leaving the salt in the bottom of the container.

Cover the bucket with a cloth (I like to use a wet towel) and leave it alone for several hours or even overnight until all the metal has dissolved. This is a powerful Aqua Regia solution. Never seal any container with Aqua Regia. It will release chlorine gas for weeks, building up dangerous pressure. BE SURE CHILDREN, PETS, OR UNWARY ADULTS CANNOT ACCIDENTALLY GET NEAR IT OR THE FUMES.

Very carefully pour or siphon off the blue, green, or yellow liquid into the second bucket without disturbing the sediment on the bottom of the first bucket. Don’t even think about starting a siphon using your mouth! I start the siphon by prefilling the siphon tube with water, putting a finger of each end of the tube while wearing rubber gloves, and then releasing my fingers once the ends of the tube are submerged in the containers. Now add anywhere from a cup to a gallon of water to the first bucket (I add very little water, it’s up to you how much you want to add). This will stir up the remaining liquid and all the sediment. Let this settle for a while. Then with a cloth filter on the second bucket, slowly pour or siphon this liquid into the second bucket, adding it to the solution you already poured into the second bucket. A sheet will work as a filter, or better yet, I like the sheer material that’s used on a wedding gown. I don’t always use a filter, usually I just carefully pour off the liquid being sure to not let any sediment carry over.

To precipitate the gold out of solution, slowly add a handful of Urea (available at feedstores) to the solution (the second bucket). If your Urea is “dirty”, instead of adding the Urea pellets directly to the solution, you may want to first dissolve the Urea pellets in boiling water and then filter it to clear any sediment. It should fizzle and it may even foam up. When it no longer fizzles upon adding more Urea you can stop adding it. It may not fizzle at all, which is O.K. (it just means that all the NITRIC Acid has been used up in the reaction). Most likely if you look very closely you will see thousands of tiny bubbles forming in the solution in the bucket after you’ve added the Urea. I like to wait 5 to 15 minutes for the bubbling to die down a good bit.

Now, mix 1 oz. of Sodium Metabisulfite into 8 oz. of HOT water. The actual amount of Sodium Metabisulfite you mix up depends on the amount of gold in your solution. Here you have to guess. You want to mix into a small quantity of water an amount of Sodium Metabisulfite equal to or slightly greater than the amount of gold dissolved in your solution. It’s better to put in MORE rather than LESS. You just don’t want to use a LOT more than is necessary. If you use too little, all the gold will NOT come out of solution, which you can determine with a gold testing solution. If you didn’t add enough Sodium Metabisulfite you can always add more. One way of knowing if you’ve added enough is the STRONG smell of sulfur coming from the solution afterwards.

Slowly pour the Sodium Metabisulfite mixture into the solution while briskly stirring. You will smell the Sulfur Dioxide being produced. Hopefully the liquid will begin to turn brown right away. If it doesn’t, give it some time. It may take a few minutes or longer. Once you see the brown gold forming, cover it with a cloth and wait for a couple of hours, overnight, or even a full day to allow enough time for the gold sediment to all settle to the bottom. I’ve found out (from one of my students) that you can heat it up at this point to around 150 F, and it will usually settle out the gold without having to wait. Test the solution for gold. You can test to see if the gold has precipitated out of the solution at any time, but the less time you wait the worse the TOXIC fumes you’ll be exposed to will be.

If there is still gold left in the solution (after you have waited at least 8 hours), mix up some more of the Sodium Metabisulfite and once again precipitate the gold out of solution.

If there is no gold left in the solution, pour off the liquid, being careful not to lose any of the gold sediment that will be at the bottom. Do properly dispose of this liquid (after neutralizing with baking soda or wood ashes). Be aware that when you neutralize the liquid it will give off strong, poisonous fumes of Sulfur Dioxide. The more Sodium Metabisulfite you used to precipitate the gold out of solution, the more Sulfur Dioxide will be released, which is one reason to try to not use more than is necessary.

Here’s another disposal method you may like to know about. The leftover solution is still strongly acidic from the residual Hydrochloric Acid. I just take the aluminum shell (stripped of all other metals) from an old 5 1/4" disk drive and drop it in the bucket of leftover acid solution. I leave it in there for days or weeks. The aluminum will dissolve in the acid and become covered with what looks like a coral reef composed mostly of copper. The aluminum is causing the copper, lead, nickel, and other base metals, etc. (plus any other precious metals you left behind) to come out of solution. I then pour off this liquid, which should now be mostly aluminum hydroxide, (which has very little environmental impact) and collect the solid residue. The solid residue is dried out, and then should be able to be recycled as scrap metal, primarily copper.

There will be a brown or black residue on the bottom. This is the gold. Rinse with clean water several times, carefully pouring it off to not lose any gold (after waiting LONG enough for ALL the gold to settle to the bottom, this could take a good while). It’s a good idea to do a final rinse with ammonia, followed with a distilled water rinse. The ammonia will remove traces of silver and other metal oxides. If the residue is light brown, you have very pure gold. If it is darker, or almost black, you may want to redissolve this residue in the Aqua Regia, and reprocess it, to make very pure gold. In fact, if you want high purity gold, it’s best to ALWAYS redissolve the residue, and do the precipitation again. This will produce very fine gold.