Did I just vaporize my Gold!!??

I set up a cell to strip gold plate from small brass parts. The parts have a clearcoat of some sort on them so I soaked and tumbed a batch in laquer thinners first. They did ok but the coating remained in some spots. Next I tried a heat gun and burned the coating off. This worked so good I put the rest ( About 5lbs) in a kiln and burned for an hour . Here is where I think things went bad.
The temperature ramped up to 1087 degrees F ( I was distracted for a bit). When I took out the parts all I saw was Nickel underplating. Did I burn off my Gold?? I was hundreds of degrees below the melting point of gold.
Can someone tell me if the gold could alloy or migrate into the nickel at this low a temp.?
thanks,
john

Your gold should still be there - if the temp was what you say it is the gold is in the metals you heated or it is in the crucible it was in! Calm down it should still be there - you are going to have to process it to find it but it should still be there!

Melting point is like 1065 C and boiling is almost twice that and you were in farenhieght RIGHT!

Some of the more experienced guys - GSP, Steve or Harold should reply to your post soon and Im pretty sure they will concur.

Glynn

John,

I would guess the thin gold layer alloyed with the nickel undercoat.

You should try one in the cell to see what happens. If you don't get the same results you did with the others, you may have no choice but to dissolve them in acid to get the alloyed gold out.

I doubt the gold went up in smoke.

Steve

lazersteve said:

You should try one in the cell to see what happens. If you don't get the same results you did with the others, you may have no choice but to dissolve them in acid to get the alloyed gold out.

I doubt the gold went up in smoke.

Steve

Click to expand...

My thoughts, exactly, although stripping with a cell may now be beyond possibility due to the gold now being alloyed with other metals, not existing as a layer.. Worth a try, however. I would expect, at the very best, a poor strip, and possibly no stripping at all due to the nickel acting as a barrier, as it's intended.

Nickel is used under gold to prevent migration of gold to the base metal(s). That may not work at elevated temps, however, so having the gold migrate deep in the alloy would certainly not be beyond reason.

As Steve suggested, the parts may well require processing with nitric now---and don't expect to see any of the gold as foil if that be the case. It will now be very finely divided and not really evident aside from some black specks that materialize in the solution. If there is any lead/tin solder included, don't be too surprised if you end up with a purple gel like substance. If you do, that is your gold. Recover all of it, then incinerate to oxidize the material, then give it a boiling HCl and tap water wash, followed up with a couple of tap water rinses. Allow all the solids to settle well each step, then when the last rinse is decanted, dissolve what remains with AR (or the method of your choosing). You're likely to recover all the gold. Do not discard any of the ash that comes from any of the incineration process----it's sure to contain gold. Include it in the process.

Harold

Thanks guys,
Whew!!!!
You were right, I put a few pieces through the cell and they still fizz. The cell seems to be working slower on these. The bubbles are not as strong but they fizz longer than before.

Or is the slower process because the cell is getting full? How do I know when it is time to filter and process the gold?

I am sorry for all the questions but I find this all fascinating!

In the cell- why does the gold not plate out onto the lead and could I use lead as the cathode as well? I am thinking about automating the cell somewhat. Maybe a lead conveyor with a water wash and a dump bucket, drop the parts on the belt let them ride down into the cell then out, drip off over the cell , get sprayed with water out board of the cell then fall off into a collection bucket of water as the belt returns under thcell to start over again.
I am just kicking the Idea around Anybody see room for improvement?

Thanks for all you help,
john

Ignatz61 said:

In the cell- why does the gold not plate out onto the lead and could I use lead as the cathode as well?

Click to expand...

The theory of sulfuric stripping cells, as I understand it-----is that in the proximity of the anode, persulfuric acid is created by the amperage of the circuit. Gold is dissolved by persulfuric, but sulfuric acid won't hold it in solution, so as the gold migrates from the anode, conditions change and the gold is automatically precipitated. I may have some of this wrong, but cells perform exactly in that fashion------thus the black or purple mud that forms. Unfortunately, I've never operated a cell, so I can't speak from personal experience. My only experience was to visit a government facility (in New Mexico) where gold was being stripped with a large cell.

I am thinking about automating the cell somewhat. Maybe a lead conveyor with a water wash and a dump bucket, drop the parts on the belt let them ride down into the cell then out, drip off over the cell , get sprayed with water out board of the cell then fall off into a collection bucket of water as the belt returns under thcell to start over again.
I am just kicking the Idea around Anybody see room for improvement?

Click to expand...

You'd have to overcome the problem of dragout and water addition. If you can prevent concentration change of the electrolyte, you may have a fighting chance, but you'd likely be far better served to build a tank that simply allows for easy cleaning, plus has a greater volume, so you can run for a prolonged period of time without recovering gold. If you increase volume, you'll need a larger power supply.

The cell I witnessed was built as a funnel, with a ball valve at the bottom. To clean the cell, the electrolyte was drained by opening the valve, and new electrolyte introduced. The cell was down only briefly. The extracted electrolyte was then allowed to settle, then reused when the cell was cleaned with the next cycle.

Stripping by time may not be in your best interest. As I recall, you know when all the gold has been stripped by the fall of amperage. If you strip with a fixed period of time, you may not recover all the gold that is present, and over run some materials that are very scantily plated.

You might be wise to dissolve a few of those pieces that you've tried stripping, the ones where you thought you'd lost the gold. It's possible you aren't going to recover all of the gold by stripping. Dissolving a few of them in nitric would prove that you had, or not.

Harold

Thanks Harold, for your reply.

I like the idea of a funnel shaped tank like you described. I am favoring a larger tank and perhaps a Stainless steel dip bucket. My reaons are 2 fold

1. I get bored dipping the parts in 1 by 1. With a perforated basket or bag like in the video I could run many parts at once.

2. I am looking at the ablity to scale up as more scrap becomes available to me.

I was aware that the gold automatically preciptated out as you said but thought it was due to the lead Cathode? So, what is the reason for the lead cathode? Is it because it is unaffected by the acid? If that is the case then could we use a lead bag or perforated container as the Anode so to speak?
lastly, And I have asked this a couple of times in various posts-How do I know when it is time to filter the acid?
Thanks again,
JOhn

Ignatz61 said:

, And I have asked this a couple of times in various posts-How do I know when it is time to filter the acid?
Thanks again,
JOhn

Click to expand...

http://goldrefiningforum.com/phpBB3/viewtopic.php?p=2970&highlight=modem#2970

Many thanks,
john

Ignatz61 said:

So, what is the reason for the lead cathode?

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I'm not sure I can answer that question, having never operated one of the cells, but I get the idea it is used because of its resistance to sulfuric acid. That need not be the case, assuming the acid is concentrated. Our very own GSP, who has considerable experience running sulfuric cells, claims that mild steel (low carbon steel) is quite resistant to dissolution in concentrated sulfuric, so stainless need not be used. It's important that water not be introduced to the cell, otherwise items that might not dissolve readily, will. I know that's true of cast iron, which is quite resistant to concentrated sulfuric, but can't withstand it when dilute.

I made mention of witnessing a large stripping cell in operation. They used baskets made of copper. For very small items, copper window screen would work quite well, and I believe Lazersteve has some for sale on his web site. For larger items, a copper basket can be fashioned from coarse copper screen. You might consider exploring something like ¼" mesh, which would have a much heavier wire in its construction than the finer screen materials. You would benefit from the heavier wire in longevity and rigidity of the basket. The basket is suspended by a pair of arms, made of copper buss bar, which become the electrical path to the basket.

Is it because it is unaffected by the acid? If that is the case then could we use a lead bag or perforated container as the Anode so to speak?

Click to expand...

Could be a basket made of lead would work adequately, but lead is not known for its strength, and would easily deform. Could be a problem, depending on size and application. In this instance I'm speaking from the perspective of a machinist, not a refiner. I think lead, in larger sizes, would be an ongoing problem.

lastly, And I have asked this a couple of times in various posts-How do I know when it is time to filter the acid?
Thanks again,
JOhn

Click to expand...

Again, without a working knowledge of cells, I may be way off course, but one indication is when amperage won't fall below acceptable limits. I would expect that when there's too much gold in suspension, the cell will conduct, even when it isn't removing any gold from the surface of parts. As I was instructed by those that operated the cell I witnessed, voltage was raised to a maximum of 28 volts before parts were removed from their cell. When amperage dropped, they considered that they had stripped all of the gold that was accessible. To give you an idea of the magnitude of this operation, they had stripped something like $35,000 worth of gold, and that is back in '75, when gold was roughly $100/ounce. The yard was filled with 55 gallon drums of copper based alloy materials that had been stripped. A rare example of government doing the right thing, the right way.

Harold

First time poster.

This is the copper basket I made for my cell that uses the same size glass dish Steve has in his video.
It started out as a 5" x 7" sheet for punch art from my local Hobby Lobby for about 7$.
I think the thickness was listed at 0.016" but don't quote me.
I started drawing it out and folding it up on paper and ended up freehanding it so I do not have a pattern to post.

I should have used a smaller drill bit when drilling the bottom & front so the pins would not pass thru them as easy.
I just used a drill bit that looked right, don't even remember what size it was.
I use a plastic fork every so often to pull the pins out of my solution and throw then on top of a fresh basket of pins to rework them.

The copper does get tarnished during use and I have to use a wire brush on it occasionally after rinsing to expose some bright copper for better conductivity.
I have used it for about 8 or 10 pounds of header pins with no noticeable reduction in thickness.

I also have a piece of 12 gauge copper house wire with a dime sized pad curled on it and then bent flat on the bottom of it.
I use an alligator clip to connect it electrically to the basket or the charger clamp so it can be easily removed.
Then when the process slows down I use it to stir up and compress down the pins to finish deplating them.
I have to make sure it does not contact the cathode or it might spit at me.
I did leave the insulation on most of it as a little extra safety measure.
(The less exposed copper on the stomper, the less likely of a accidental short to the cathode.)

I now have piece of copper flashing material from a local roofing contractor.
It must be 0.025" or .030" thick and will be more difficult to bend.
I do not belive I will change the size ot the finished product.
It extends a little less than half way across the dish and I feel safe with that distance from the cathode.

Thanks & keep up the good work on the forum!
Ideal-Wirenut

ideal-wirenut said:

I now have piece of copper flashing material from a local roofing contractor.
It must be 0.025" or .030" thick and will be more difficult to bend.
I do not belive I will change the size ot the finished product.

Click to expand...

If you find it difficult to fabricate, heat it to a dull red, then either allow it to air cool, or quench in water. That will soften it such that you'll be able to bend it with your fingers. Material like that has work hardened in the rolling process and is quite rigid unless annealed.

You might also consider making your baskets from copper screen, saving you all the trouble of drilling the holes.

Harold

I just finished refining the gold I stripped in my cell. After all the little problems, I got just over .5 grams of gold from about 5lbs of plated brass parts. the overheated parts stripped ok, when I filtered the acid (after diluting it) it came back clear! I did a few things alittle different than Stve did in his videos. Most were poor choices.

I did not have a lot of sludge from the small amount of electro-stripping I did, so I burned the filters with the sludge. (I have a small digital Melter with graphite crucibles I use for casting jewelry as a hobby)
the paper chared but did not vaporize as I hoped it would. It was more like throwing a stack of magazines on a fire. They burned slow and left a chared mass behind. Afraid there might be gold stuck in the mess I cut down the crucible and burned the whole lot with a torch. It took hours to get the paper to burn off !! Then I was still left with a sticky mess of boric flux. That took a long time to reduce.

Finally I started to see little beads of gold forming as the flux disappeared. I got most of it to form a ball that I wieghed once cool. But I noticed many more little beads stuck to the sides of the crucible. I tried for quite a while to coax them down together with the torch but they would not cooperate. I finally broke up the crucible and will disolve the gold with hcl-cl.
Steve used a cupel, is this much better than graphite? Or, was I doing something else wrong?
Can you use too much Boric acid flux? It seemed like the gold didn't come together in a bead until the flux dried up (burned up)
Is it better to wait until you have more gold so the larger bead or puddle absorbs the little beads?

lastly, can someone tell me Is copper a better material to make a basket for a cell or will Stainless Steel work better?

Thanks,
JOHN

John,

The cell melting videos are out dated. Back then I used cupels for all my melting, now I use melting dishes. I guess I should remove that part of the cell videos.

Before you torch any gold from the cell it should be dissolved in HCl-Cl first. This is another improvement I've made tot he process along the way.

I've removed the cell smelting video to clear up any confusion in the future.

Steve

Steve the videos worked, Even making mistakes I still got the whole mess to work based on what I learned from them.

Anyway, it's still basically the same melting procedure right? After precipitating the auric cloride you dry and melt the caked mud until it forms a bead of gold, right?
Is the material the melting dish is made of smooth? The graphite becomes rough when heated for awhile and I think that caused some of my gold to "hang up" rather than slide down the sides and form a nice big ball.

What is the advantage of using the hcl-cl? Better purity?

Thanks for all your help,
John

ps. I am in the process of making a small (21" dia) ball. I am looking for any input I can get as far as what makes a good ball mill, but this may be better in another thread.

John,

The new melting procedure is found in the last section of videos on my website. It incorporates several techniques that I learned after joining the forum. The old way worked for me back then, but the new way is better all around.

The HCl-Cl helps to purify the black powder from the cell by dissolving the gold which allows you to selectively precipitate the gold from the solution before melting the powder. You should also do the standard boil in water x3, boil in HCl x3, and water x 3 washes (in that order) on the precipitated gold for maximum purity.

Steve