Trouble Precipitating from HCl + Bleach

So, I've tried searching high and low on the forums and found some posts that are similar-ish to what I'm experiencing, but nothing close enough to the same to give me enough to plan my next move.

I've run a few batches of fingers and Karat gold and had good, predictable results in the past. Recently, I ran some very low quality fingers bought years ago in a fit of ignorance. I ran them through AP and ended up with the foils similar to past runs.

In the past, I'd then use HNO3 and HCl to make AR, but this time I did things a bit differently. This time I used HCl and bleach, being careful to not over-add the bleach. I heated the resulting lime green solution to de-gas it. That produced the rich golden yellow and clear solution I was expecting.

This is where things went weird. I added SMB (no idea how much gold is actually in solution). This resulted in a dark cloudy solution as expected, however, 12 hours later it hasn't cleared at all (even after chilling).

Worse, this "produced" a thick precipitation of white or grey white something on the bottom. I wasn't expecting that at all and I have no idea what it is. Is it a salt? Is it undissolved SMB? I wondered if maybe the PH wasn't acidic enough for the SMB to precipitate the gold, so I added a little more HCl. No change.

Now I've been reading that SMB might not be the right precipitant in this case (that Sodium Hydroxide would be better). Either way, the SMB has been added, so I'm assuming that ship has past. Not sure what to do next.

Any help would be appreciated. Thanks.

Are you doing this on a balcony in an apartment complex?

Dave

Nope, but I brought it back there after being frustrated with it and calling it a day.

Do not use sodium hydroxide. Most probably the precipitate is either SnO2, CuCl, and it traps the gold inside

Lino1406 said:

Do not use sodium hydroxide. Most probably the precipitate is either SnO2, CuCl, and it traps the gold inside

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It's most likely salt if there was no water used to dilute the solution. Add some water and it may well dissolve.

Lino1406 said:

Do not use sodium hydroxide. Most probably the precipitate is either SnO2, CuCl, and it traps the gold inside

Click to expand...

I can't really see where tin would have entered the solution, although I suppose it's always possible is some of the fingers weren't properly trimmed. Assuming that's what this is, what's the next step? If the precipitate has trapped the gold then cementing on copper wouldn't be possible, right?

anachronism said:

It's most likely salt if there was no water used to dilute the solution. Add some water and it may well dissolve.

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Brilliant. Attempting that now. Fingers crossed.

Water addition = no change other than the solution now looks more dilute.

I'm legit stumped. Nothing was out of the ordinary with this process other than using HCl + Bleach vs. HNO3. There might be an excessive amount of SMB as well but not a horrific amount. I don't think there's really that much in values in this, I'm getting to the point of chalking this up to a loss and going back to using Nitric from now on.

Any help would be appreciated.

Thanks.

Stannous test your solution. If the gold is there filter off the solids and drop again. Careful not to over add the SMB

Wash the solids in hot HCL filter and rinse with hot water (distilled)

Terun what's left in the filter in AR. Stannous test an drop as usual pending a positive test of course.

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How much heat and how long did you heat it?

To much heat, to long, can kill the HCl as well and it is needed to convert the SMB to the gas need to drop the gold. (Brain is numb, I think that gas should be S02) As Rick said, test it with stannous to be sure your gold is still in solution first.

Bleach (sodium hypochlorite) easily dissipates when left in the sun. It really shouldn't take much heat or very long to remove it.

So confession time, I've never used Stannous mostly because in Canada, things like Solder or split-shot sinkers don't list the metal composition, just "lead free" at best.

Having said that, I mixed up some solder and HCl and used that to test the solution. The result was no change in colour, leading me to think the gold has in fact dropped out. I'm thus probably going to decant and wash the solids in distilled water then HCl a few times and see what's there.

If you have other gold items, put them in AR and test your Stannous in as known solution. If it test positive then move forward with this project.

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Does your bleach have sodium hydroxide in it?


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Hello, get some pure tin shot and make some stannous chloride testing solution.

https://www.ebay.ca/itm/15oz-Tin-Metal-Shot-99-9965-Pure-Element-Sample-425g-High-Purity/111898435302?hash=item1a0daa9ee6:g:vTUAAOSwUuFWto5b

Just dissolve some a few pieces of tin shot in HCl and its ready for use, but it's only potent for a day or two.

That way you can be certain you have gold in solution before you add precipitant.

Give me a shipping address and I'll send you a gram of stannous crystals and a gram of pure tin shot.

With the recipe on how to make it - it lasts for up to three months.

kadriver

kadriver said:

Just dissolve some a few pieces of tin shot in HCl and its ready for use, but it's only potent for a day or two.

That way you can be certain you have gold in solution before you add precipitant.

Give me a shipping address and I'll send you a gram of stannous crystals and a gram of pure tin shot.

With the recipe on how to make it - it lasts for up to three months.

kadriver

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Nah that's simply not correct. Stannous made of pure Tin lasts an age. If you're adding Tin to HCl you're making Stannous Chloride- exactly the same stuff you buy as Stannous Chloride. 8) 8)

Jon

Kind offer though