Looking for choice process

[jason_recliner]

I've got a pile of Bluetooth stub antennas. This sort of thing:

After ripping off the plastic and pulling out the steel wire, they're a gold plated nut, probably brass or steel, and a Teflon spacer. I'm hoping to end up with a whole lot of them. My first test was with 25.

I put them into some HCl + H2O2 a few weeks ago. The gold has slowly flaked off as the acid gets underneath. Most of which is not visible in the tilted jar, and I think the plating was thinner than I expected anyway. But because the base metals are relatively enormous to the gold, and there's Teflon in there too, it's tricky to filter all the flakes without leaving some behind on the rubbish. It's gone largely green but I'm not sure whether I have cupric chloride, ferric chloride or something entirely different.
Here's a pic so far. Might the whitish powder in the middle (and elsewhere) be silver?


What do you think about the idea of processing my next test lot by adding a little NaNO3 to the HCl. (I've not found a source of nitric acid yet.) The idea is that the gold would dissolve first then I can toss the rest, and refine / cement out the contaminated gold but without losing so much. Could it happen that the gold plating won't dissolve until the base metal is gone?

 

[solar_plasma]

The whitish powder is most probably CuCl and will dissolve, when enough HCl is available. My two cents are, that the only time economic method is the sulfuric cell. Since I always only had some single pieces, I just processed them together with pins in aerated CuCl2 leach (AP) at temperatures above 20°C, much faster with heat by "Göran's coffee maker". It takes some more days, than dissolving pins, but it works. My pieces have always been copper. I do not see any gain or even sense in using any kind of AR for this.

After all, I have come to the belief, that the more experience you get with CuCl2 the faster it works, because you get a feeling for optimal aeration, temp, knowing when to add HCl or sometimes boosting with a shot diluted H2O2.

 

[solar_plasma]

I did not see your last question. You have to dissolve ALL base metals. There is always the chance some gold gets dissolved and plates back on the base metals by replacement. Those tiny amounts of gold will hide between the enormous amounts of base metals.

edit: Since you used H2O2 in the beginning (gold dissolved - oxidating environment) and have some CuCl powders in the bottom now (relatively more reducing environment), I am pretty sure most of your gold is cemented onto the base metal pieces.

 

[jason_recliner]

Thanks. This is something that has long confused me and I can't find a comprehensive answer.
Will AP (HCl + H202) actually dissolve gold? I thought it was not meant to; that one needed AR. Or at least HCl + a nitrate. Am I tossing gold???

I can't get nitric acid. And despite watching half a dozen different methods, I'm not comfortable yet with making my own. So it's AP for base metals, then poor man's AR to dissolve the gold in what's left.

 

[butcher]

It depends on the strength of the hydrogen peroxide; strong Hydrogen peroxide will dissolve gold, as it will form chlorine gas with HCl.
There are several ways to dissolve gold, and many more ways to loose gold.
Study will help you learn more.
A whole lot more.
There are lifetimes of knowledge and skills to learn in this art of recovery and refining.
Study can also lead you to those choice processes you are looking for, many things you can use to find and learn recover and refine those precious metals.

 

[jason_recliner]

I hear you Butcher. I actually read a fair bit. Several times a week. Though I don't understand everything I find. Especially a lot of the chemical reactions. So I have to go by what is known to work rather than make my own reaction equations. I've spent about an hour today just trying to find out whether gold can dissolve before the base metals, and have not found a definite answer. Which is why I posted.

I'm using 3% peroxide. If this is too weak to dissolve gold, then it follows that it's not cementing back on to the base metals. Solar_plasma may run with say 30% H2O2 and that's my fault for not clarifying that I don't have it that strong.

My previous batch had the problem of too much nitrate salt. It took some getting rid of, but was eventually a success following Hoke's evaporation method. It would have been easier if I'd had extra gold to drop in. And maybe I can use that to my advantage now. If I add enough sodium nitrate that the gold goes into solution, when it's stripped I could separate the nuts. After testing that more metal can still go into the removed solution (still enough nitrate), I would know that there is no gold cementing and the nuts could be dumped (after a but more HCl and a stannous test, of course!). Then a copper busbar to use up the remaining nitrate and cement out the gold.

It does still assume the outer layer of gold will dissolve before the more reactive base metals inside have vanished.
Is my logic sound? Or have I failed to account for something else? Thanks guys.

 

[solar_plasma]

I hear you Butcher. I actually read a fair bit. Several times a week. Though I don't understand everything I find. Especially a lot of the chemical reactions. So I have to go by what is known to work rather than make my own reaction equations. I've spent about an hour today just trying to find out whether gold can dissolve before the base metals, and have not found a definite answer. Which is why I posted.....

It does still assume the outer layer of gold will dissolve before the more reactive base metals inside have vanished.
Is my logic sound? Or have I failed to account for something else? Thanks guys.

If you were a very reactive chlorine atom in an oxidizing aqueous solution you would interact with the next more or less reactive atom that comes your way. When you meet a gold atom, you don't know, that at a distance of some hundred Ångströms there is a more reactive copper atom. Now you have married this gold atom and given it your ring (an electron), but you aren't really satisfied, you will run with the next lovely copper atom, that will cross your way, taking your ring back, giving it to the copper babe, leaving the lonely gold atom behind. Sad story. Especially if lady gold now hides between the undissolved base metals, being tossed away by the unknowing.

That is so much simplified, that it isn't really correct anymore, but it might be correct enough to be a model to understand, why the base metals have to be dissolved completely and why gold might dissolve and then cement back.

 

[jason_recliner]

:lol: What an analogy!

Now I understand WHY:

You have to dissolve ALL base metals

Regardless of the method.

Looks like I'm gonna be needing some more acid and another month. Thanks and well done on the explanation.

 

[solar_plasma]

There are only two ways to build new connections between neurons, commonly called learning, - repeated exposition to a weak stimulus or exposition to a stimulus that is combined with emotions. The analogy is effective, because it is reaching our mirror neurons, that also are the reason for empathy. A story of love, dissatisfaction, feelings of guilt and sadness is a strong emotional stimulus.

I am glad, if I could help a little.