Never-ending SMB Reaction

[TheCygnusJourneyman]

Hello everyone. I'm new here. Please be patient with me.

I created around 1.5L Aqua Regia in a 3L glass jar and dumped just about every gold and gold-plated scrap I had into the solution (around 1kg of scrap, mainly gold plated jumper pins, processor pins and gold fingers). I heated the heterogeneous mix against a gas stove so that the reaction would go faster. I let it cool and react some more overnight, and the next day the solution turned into sarsaparilla in color, barely translucent. I decanted the liquid into another 3L jar.

I have tried to increase the pH level by adding a litre of diluted urea. Then I added some Sodium Metabiulfide to drop the gold. Unfortunately, besides a violent fizz with lots of noxious fumes, there doesn't appear to be any mud or slurry dropped. So I just kept adding more and more SMB and stirred a lot during the day; and more fizz and fumes occur, but no gold drop. Now a question: could the pH of the solution be too high (thus having to add more urea), or do I just have to add more SMB?

If this comment is as dumb-a$$ as can be, please forgive me.

 

[Lou]

We'll be plenty patient, but you're doing a lot wrong and it can easily go from wrong to very bad given how you're doing things:

1.) Don't premix your aqua regia, start with HCl.
2.) Do not use a jar, use borosilicate (Pyrex is the brand) glass especially considering...
3.) you're using a gas flame--don't use a gas flame!
4.) Don't just toss in material--what you're doing is dissolving all of the base metals and then putting the gold in solution. You're doing a lot of work for basically no return
5.) work with smaller volumes to start with!

Learn how to strip the gold off of the material. Don't try bulk dissolution, and for Pete's sake, keep jars off the gas range!!

With that much aqua regia that's not been properly denoxxed (removing the nitric acid that you had in >10,000% excess to the gold), you'll be adding SMB till the cows come home from the abattoir! :/

 

[TheCygnusJourneyman]

Lou, you can pat yourself on the back...

You just saved this little black duck - at the very least financially - from running into disaster. Common sense - let alone Hoke's book - should tell me that the base metals of the PCB chunks will be dissolved with the gold in the aqua regia. I wasted about an ounce of filtered gold flake from a previous mix of HCl (what you actually told me to do!), but I decided to screw things up and add it into the mix, didn't I. :roll:

I won't. Ever. Use a gas stove while doing gold recovery. Again.

 

[Harold_V]

but I decided to screw things up and add it into the mix, didn't I. :roll:

Do be mindful of not alluding to the F word on this forum, please. 8) (Note that I have replaced your figures)

I won't. Ever. Use a gas stove while doing gold recovery. Again.

Lou's comment are dead on, although if you use the proper pads, gas works perfectly well. I used natural gas for heating for my entire refining career. You do have you use good sense, however. It's easy to break borosilicate glass when it's heated unevenly.

Harold

PS--

A comment on our experience. Wise people don't toss everything in AR unless they really enjoy making a mess, and risking the loss of values. Learn to eliminate base metals before dissolving values. The end product is so much nicer, and the risk of loss is much smaller.

All is not lost with your project. In fact, if you still have base metal present, you may have effectively eliminated a good portion of that which you should have eliminated initially. The values will have been dissolved and cemented on the remaining base metals, so the sludge you find in the bottom will be the values, even when they may not look like gold. Learn from this experience. There are much better ways to process.