2 question on acid peroxide method

[mls26cwru]

I have a couple questions on this last batch that I did and hopefully you guys can help out a bit. I did a batch of gold fingers and i feel that the yield is a tad bit lower than what i was expecting, so i went back and analyzed what i did and came up with a couple question.

First - I started with an impregnated solution of copper 2 chloride and let the solution run with a bubbler going for a couple days. I noticed that most of the gold had flaked off but the fingers still had the copper under layer attached to the pcb part of the fingers... I didn't think much of it assuming the C2C had dissolved enough of the copper away to let the gold flake off... upon thinking a bit about this and doing a little searching, is it possible that the any gold has cemented back onto those copper traces left over? should i throw the fingers back into solution and let the copper totally dissolve off the boards?

Second - after the initial filtering of the C2C solution i was left with a bunch of gold fingers and a second container full of the water used to wash my filters. this second container had a lot of black powder mixed in with a lot of pcb fibers. it was washed and then I left this solution to decant for a couple days and the powder did not want to settle easily. I took siphoned off the decanted solution, put it back into my original C2C bucket, and added about 30ml HCl and a capfull of bleach to what was left. The solution took on an immediate yellow hue. I added about 4 - 5 capfulls more of bleach... each time it would fizz vigorously... on the 6th capfull, the fizzing finally had stopped. I filtered this solution and it was a strong bright clear yellow (auric chloride). I put this solution into a bigger beaker and added about 3 times the amount of water to dilute it. Not knowing how much Au to expect, i added about 3 grams of SMB. The solution turned clear, but almost nothing dropped out of solution. I waited for about 18hours, went back and no change. added a bit more SMB, and nothing extra happened. I finished processing what little precipitate i did have, and only ended up with about 0.15 grams... Is this normal? can such a little amount of gold make auric chloride that bright yellow? I just felt like there should have been more judging from the color of the solution. any thoughts? did i miss any steps?

for some reason i just thought that I would end up with a bit better yield than i did. I just wanted to run it by you guys and see what you all thought. Thanks for reading!

Mike

 

[butcher]

Mike,

A couple of things come to my mind here.
I would want all of the copper dissolved, the fact you had a black powder possibly gold, is an indication gold could plate back to the remaining copper metal.

Also as you know it is very important to keep tin out of solution. If gold and tin are dissolved the gold is reduced to colloidal gold which will not settle, tin will also reduce copper II chloride to copper I chloride (a white powder), remember stannous chloride SnCl2 which is made with tin and HCl if mixed with gold in solution will give us a colloidal gold solution that will not settle (the violet color of gold we see in the stannous chloride test) it can also do this in other solutions.
See formulas below:

2AuCl3 + 3SnCl2 --> 2Au (colloidal gold) +2SnCl4
2CuCl2 + SnCl2 --> 2CuCl + SnCl4

Remember the bleach is a basic solution, your HCl is acid, mixing the two will make a neutral salt solution (we want to keep the solution acidic) so we need to be careful with adding too much bleach or neutralizing it.

If we have free chlorine in solution our gold will not precipitate, but can re-dissolve in solution, causing one to add too much reagent to precipitate gold, or not to be able to precipitate the gold.

I do not see where you mention using stannous chloride to test your solutions, how would you have any idea of where you are at if you have on a blindfold.

I would not use colors to judge a solution, use your tests and testing procedures to do this.

I cannot comment on if this may be your problem with suspecting low yields.

 

[bswartzwelder]

You made a type of AR (acid/bleach) and added it to a AP (acid peroxide) mixture. Nowhere on this forum have I ever heard of anyone attempting that. Did you test the original AP solution with stannus chloride? If not, then you were shooting in the dark. I would suggest you put everything away and start reading Hoke. Read every thread on the forum dealing with acid/peroxide. Then read Hoke. Next, read every thread on the forum dealing with AR and/or acid/bleach. Then read Hoke. One thing you will find the members adamant about is reading until you understand the different processes. While you're reading, read as much as possible about safety. Before you start throwing chemicals together, read the MSDS associated with that chemical. Have a bucket of water nearby for when something splashes out or one of your containers breaks. Without the proper safety gear, the question is not one of what is going to happen, it's when is it going to happen. If you aren't prepared and you know little about what it is you're doing, you might take up a slightly safer hobby like Russian Roulette.

People here are not likely to take you by the hand and offer step by step procedures. There are plenty of them already written. They are here on the forum and in the masterful book written by Ms. Hoke. The chemicals you are using could maim you, blind you, or kill not only you, but your friends, family, neighbors, and pets. Nothing is worth that.

Put a lid on everything and put it away. If there was gold in there, it's still there and won't be going anywhere. If you continue shooting in the dark, you could lose all values or make it almost impossible to recover them. Sit back, relax, get one of your favorite beverages and if I forgot to mention it, read Hoke. You may think that not getting a direct answer to your question is not what you wanted, but take it from someone who has lost values, it saved me far more in the long run than I ever lost.

 

[butcher]

bswartzwelder,
They way I read what he did, it did not sound to me, like he mixed the two solutions.
I think he is just talking about the two processes in the same post.

 

[g_axelsson]

I think that you could still have gold in your solid leftovers. The fizzing when mixing bleach in hydrochloric acid is just the chlorine gas release when it reacts with the acid. The fact that you didn't get any fizz at the end tells me that you probably have exhausted the acid. This will put a stop on the dissolution of the gold and leave any gold left with your solids.

Do another leach but this time add the bleach in small additions over time.

If I'm wrong you will have wasted a bit of time, but if I'm right you will get your lost gold.

Btw, how much material did you start with? I couldn't find anything about it in your description. And tin chloride is your eyes in refining, don't walk around blindly. If you suspect any more gold in solution, test it before adding more SMB, you can't drop anything that's not there.

Göran

 

[mls26cwru]

thank you for the replies everyone. I realized this morning that I had forgotten to mention that I had tested the solution with stannous but couldn't log on to add that to my description. I once i diluted the auric chloride, i added SMB, and the color disappeared and a little precipitate dropped. I was expecting more, but assumed maybe i still had chlorine in solution, so i let the mix set until the next day. nothing had changed so i tested the clear liquid with stannous and there was no color change. I saved all the liquids and they are sitting in a separate jar at the moment and I came here to get some opinions.

just for clarification I filtered the copper chloride solution, washed filters, washed powder with hot water, decanted, dissolved powders in HCl/chlorox. I did not mix the acid peroxide solution with the acid chlorox solution.

Thanks!
Mike

 

[mls26cwru]

Butcher - thank you for the tips... this is what I was looking for.

I will throw the fingers back in the C2C until all the traces are gone and hopefully a get a bit extra with the next batch.

As for the Tin getting into the batch.. the fingers were pretty well cut. somehow, two drywall screws made it in to the batch which caused some copper to precipitate and got tied up in my very first filtering attempt... i put that into a container and made a 'mini batch' of fresh acid/peroxide and the copper dissolved right away leaving nothing but foils. that was filtered and everything went smoothly from there. could the two drywall screws formed colloidal gold someway?

Also, for those that asked about starting material. I processes 5lbs of fingers and have reclaimed 8.5 grams of gold (from the foils). I realize that this is pretty close to the 2gr/lb average, but what made me think I had missed/messed something up was when i dissolved the black powder from the decanted solution I mentioned in the first post. It had such and intense yellow color to it that I thought it would contain more gold than it did. If it had been a pale yellow, it would not have really concerned me. The powder i eventually recovered (after decanting and water and HCl rinses) was nearly black and only about 0.15 grams. Since I am still new to this, I wanted to ask you guys to see if there was something i missed.

 

[butcher]

The iron in the drywall screws could have replace copper from the solution, and dissolved some iron into solution, if they were zinc coated it could have replaced some other metals.

 

[Owen_Lindsay]

Soooooo,, the hassle of applying to the home office for a chemicals licence nearly killed me in my tracks..

Instead I made my own dilute nitric acid using copper, salt Petre hcl and 12% h2O2,

Sorry I can’t get the chemical formulae to look right on this keyboard.


I’m doing a low heat nitric treatment on very rough gold filled scrap, picked out All the obvious stainless steel and ferrous metal,

As I say the scrap is very rough In quality , will I run in into problems later ??

I plan to do this slow simmer / warm treatment and keep adding the dilute nitric but the issue is I am running it so low on heat as to make best use of the nitric acid,

I’m aiming to minimise the evolution of nitrogen dioxide and minimising nitric acid loss this way.

As I have it so low on the heat I’m not getting evolution of any red gas ( high heat does produce it), do I just monitor the metal for effervescence to determine when base metal is all dissolved or should I whack up the heat once in a while to see if I get any further evolution of nitrogen dioxide?

Trying to do this cautiously and efficiently as I don’t know how strong the nitric acid will be .so I can’t use calculations that I’ve read / seen as the approximate use of 3-3.5ml conc nitric acid (70%) per gram of Gold filled scrap diluted with distilled water .


Any pointers guys?

The process does look like it’s working but I don’t want to jump to the step AR too early and get caught out with lots of messy base metals, I have some dilute sulphuric acid on hand to take care of any lead as well .



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[anachronism]

Soooooo,, the hassle of applying to the home office for a chemicals licence nearly killed me in my tracks..




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Hi there. Can I ask what nearly killed you?

 

[butcher]

Instead I made my own dilute nitric acid using copper, salt Petre hcl and 12% h2O2,

Dilute nitric or poor man's aqua regia?

 

[Owen_Lindsay]

It was the application form process? My GP is not the easiest of people to talk to and I had a brush with depression a while back, as such my GP didn’t even take the time to read the form, he just said no..

Until I get round to switching GP’s I’m kind of stuck.

As for the process, unless I’m mistaken
it is indeed dilute nitric acid.

Salt petre, added to copper , then added HCL, bubbled through 12% hydrogen peroxide done outside with the peroxide bottle sitting in near freezing water.


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[butcher]

I do not understand what GP or GP's is referring to?

I can not see how you have a dilute nitric solution, unless you are somehow distilling and capturing NOx gas into water...

Otherwise, it is a dilute form of aqua regia, as long as you have nitrates and chlorides in an acidic solution.

 

[g_axelsson]

You use the NOx given off in the copper + poor mans AR (nitrate + HCl) and bubble it through another vessel where you capture the NOx in hydrogen peroxide. It will produce a weak nitric acid with possible some traces of HCl from the fumes given off. If you like to remove the chloride you can do it with a bit of silver nitrate.
I think Nurdrage have a video on youtube showing three different ways to make nitric acid and this is one way.

I guess that GP is some kind of government official that handles the application for using and buying nitric acid.

Göran

 

[Owen_Lindsay]

Sorry , yes I failed to mention GP stands for general practitioner ( doctor). Since we had acid attacks in the U.K. certain acids and precursor chemicals are restricted for sale to
The general public. A licence must be issued by the government but in order to apply for one you must get your doctor to sign the form if you have had depression within 5 years. My doctor is a jackass!!!

I checked out the nurd rage video, same process except I only have 12% peroxide not 30% .

If any hcl comes across will it cause issues dissolving base metals due to formation fo silver chloride or will the hcl quantity be low enough that it should not cause problems ?


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[butcher]

I would prefer using sulfuric acid or a Bisulfate-based salt to make nitric acid the sulfuric acid or sulfates are not as volatile, the nitric can be made stronger from the beginning...
Sulfuric acid or its salts should be available in every country if nothing else in automobile batteries.





If using hydrochloric acid, HCl gases will come off after most of the water and NOx fumes which easily can contaminate the nitric acid with chlorides, you could use silver to remove the chlorides to purify the nitric acid solution, and concentrate it by evaporation.

Page 32 shows how to generate NOx gases with a saltpeter and sodium bisulfate salt to make NOx the precursor for nitric acid, NOx gas mainly nitric oxide gas and nitrogen dioxide gas, once bubbled into water, the nitrogen dioxide (NO2 gas) will convert to nitric acid, the nitric oxide portion of the gas is not water-soluble and will need oxygen to convert it to nitrogen dioxide before it will dissolve into water to make nitric acid, adding some peroxide to the water will help in the conversion of the nitric oxide gas to nitrogen dioxide which will then convert to nitric in the water...

Now add some cut up gold plated copper(pins) in with this and you can make copper sulfate, distill nitric acid, and recover the gold in one operation Killing more birds with one stone.

 

[Owen_Lindsay]

Awesome , thank you for the pdf ! And the advice [emoji4]


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