# Learning the hard way, Dissolving my gold, Beginner’s Hints



## AquaRegia (Nov 1, 2020)

This is my first attempt and so I used only a few connectors. I happily made my gold in copper chloride with 3:1 HCl and H2O2.

In the videos and reading such as Hoke, it seemed easy enough. I should have done the stoichiometry and thought more. As everyone says, beginners are impatient and use too much acid. Guilty.

So I had a nice little coffee filter of gold and flake-size debis that I could not pick out. I put it in a 1L beaker along with 3 other filters with very minor gold. Mistake. Now I have 4 filters in a 1L beaker and it took 200ml of HCl just to cover them. I’m already using way too much acid for my paltry gold, but I have no real idea how much to use. If I had thought it through, I had less than a few grams of gold and so it would almost certainly be my limiting reagent in the reaction. 

Anyway, I started adding Bleach. It kept fizzing and getting yellower. I stirred a lot. I saw some dissolve, and it turned yellower pretty quickly, but I had a lot of acid and assumed my debris was all gold or plastic at this point. Wrong.

I kept adding bleach, stirring, waiting... I heated it. I decided to use more HCl because now I had lost track of my ratios. I darn near filled a liter beaker with acid and bleach. This took six hours. To be fair, I didn’t know how much to use. I should have started with 100ml bleach max (for the 200ml of HCl). Again, Gold was going to be the limiting reagent. I also should have realized my acid would not turn deep golden color being so diluted. Proper yellow at 1L was pretty good. I also should have realized that it does not take 6 hours of adding, stirring, heating, etc. but I still had some gold I dissolved (I thought)! And I had no idea how long it takes as videos jump to the end a lot.

Then disaster struck. My near-full 1L beaker fell off my burner and spilled all over my backyard table and deck. I had never heated 1L before - that is heavy!

After hours of cleanup and fume ingestion, I saw a bit of undissolved “gold” in the beaker remnant. I tried it over again with what I had left and much less acid. A more careful approach this time.

Nevertheless, I could not dissolve that gold. A few hours, and even overnight, I had a barely yellow solution with copper/gold colored something in the bottom. I finally realized this is not gold. Maybe it was some nickel copper alloy, I dunno. All that glitters...

Day 2: I bought a $5 container of gold flakes and put some in a small beaker. I put 20ml of acid on there. This time, after only two droppers of bleach, minor swizzling, and maybe 5 minutes it was all dissolved into a beautiful yellow. It is quick with small flakes of super thin gold! I still probably used 10x too much HCl given that two half-full droppers of bleach were more than enough. No heat needed. Minimal stirring.

1) Handle the stuff with care
2) Use common sense for how little acid and bleach you need. Probably not much at all. Gold will almost certainly be the limiting reagent. Keep the HCl reasonable and use the minimum bleach after that.
3) Use the right size containers, it will limit your enthusiasm. The smaller, the better.
4) Not everything is gold - see #5
5) Make stannous chloride first, not after  I still have not done this
6) Be patient. Stop and think if you are not getting results.
7) If your gold is limited and in thin leaves, the reaction will be quick. You probably don’t need heat.

In the end I have just about 20ml of Golden acid as a souvenir. It is too little to drop and frankly was bought in flake form. Now I need computer parts again. I can probably scale at this point.

Extra credit: I made some beautiful art dropping sanded nails into my pickle juice overnight from step 1 where I extracted the gold. This is not the beautiful pure copper crystals that you get from replacing just copper ions in HCl. When the iron replaces the copper ions in solution, I seem to have precipitated some other metals (nickel?) and created some iron oxides and hydroxides too (perhaps the iron and H2O2 reacting). The copper is heavier and at the bottom, with sponge like brown growth on top of it. The solution turns an almost clear blue-green. I can explain the iron copper substitution in HCl, but the rest of it with mystery metal and leftover peroxide is interesting. A picture is quite striking. Worth the fun since you have the solution already (unless you reuse it).

Thanks for reading. Follow my blog at Blogspot.bravenewchemist if you want. Mostly not gold related. 

I’ll post the reactions and molar masses later. Maybe pictures too.

-AquaRegia


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## AquaRegia (Nov 1, 2020)

As promised with math:

Simplified... Not showing the formation and action of chlorine gas during the reactions...

2Au + 3NaClO + 8HCl -> 3H2O + 3NaCl + 2HAuCl4

Yes, hydrochloric acid, bleach and gold makes table salt, water, and chloroauric acid. Presumably this is mixed with whatever unreacted reagents remain such as water from diluted chemicals and excess HCl. Unless you got the bleach *just right* you have excess of that as well. The excess bleach and excess HCl make more chlorine gas, even more water, and even more salt. You don’t want any of this, so don’t use too much bleach.

The gold is oxidized by chlorine gas to form gold (iii) ions that combine with 4 chloride ions to make chlorauric anions. These join protons to make the heavy golden acid.

I used 5% bleach and 31% acid, so beware the dilution... and density for converting to volume from weight. Otherwise molar masses are:

Au 199.97 g/mol
NaClO 74.44 g/mol
HCl 36.46 g/mol

H2O 18.02 g/mol
NaCl 58.44 g/mol
HAuCl4 233.43 g/mol


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## AquaRegia (Nov 1, 2020)

I triple confirmed my understanding, I opened my bottle of chloroauric acid with excess H2O and HCL.

I added two gold flakes, close the lid, shook and waited 10 minutes. They were unaffected. No Chlorine gas.

I added half a dropper full of bleach. It fizzed. I put the lid on it and it seemed to be dissolving. I shook the bottle for 10 seconds or so and all gone!

I let the bottle sit a minute, went outside, held the bottle away from me, opened the lid and <poof> went the chlorine gas out. I closed the lid and all is well with the world.

No fumes inhaled, no excess chemicals, no mistakes or messes to clean. No beakers used. Just my dropper to wash.


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## FrugalRefiner (Nov 1, 2020)

Two things concern me.

Fist, unless your "bottle" is designed to withstand pressurization, putting a cap on it during active reactions could lead to a serious accident.

Second, when you say you "went outside", I have to ask where you're conducting your experiments.

The first rule is to be safe.

Dave


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