# Sulfuric cell & AR question



## aptus (Dec 16, 2012)

Thank you for the warm welcome and replies to my earlier question. All has been most helpful. After more reading and more studying, I am left with still some confusion and I again seek help. 

1. The purpose of the sulfuric cell is to strip the gold off the base metals. It appears that this is the same purpose of the AR method and even after one uses the sulfuric cell to stip the gold, one needs to then use the AR method prior to melting. Is the AR method simply to rid the black powder from the cell of the base metals to end up with a pure end product?

2. Can one melt the black powder obtained from the sufluric cell ? (of course contaminated with base metals)

3. If one did melt said black powder, could one at a later date run the melted ball in the AR to obtain the pure gold? (I simply am not comfortable trying the AR method quite yet)

4. Can the black powder from the cell be saved and kept for a period of time and if so would I leave it in the sulfuric acid from the cell or rinse and dry it?

The links provided in replies to my previous question were very helpful. May I be doing something wrong when I use the search as everytime I enter something in it it says nothing found. I tried basic searches such as HCI and SMB with the same results.

Thank you in advance once again. I compliment all for one of the most informative and helpful sites on the web.-Aptus


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## butcher (Dec 16, 2012)

1.Yes aqua regia is to dissolve gold (without excess base metals), to refine the gold, dissolving the gold, filtering off what is insoluble, and leaving minor impurity in solution when gold is precipitated as a more pure product, this may need to be done twice to get the gold more pure.

2. Yes but why, you are so close to the finish line: why not take that last little step and cross the line and win this race, otherwise why not just send your scrap to a refiner and not even enter the race, or save the powder until your ready to step over.

3. Just save up the dry gold powder till you are comfortable.

4. Rinse and dry it will last forever store in glass (I would not use a metal lid which will corrode if the powder was a bit acidic).

5.Have you tried the search engine on Laser Steve’s web site?


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## element47.5 (Dec 16, 2012)

At the risk of exceeding my own knowledge on this...

When you say "the purpose of the Sulfuric cel is to *strip* gold off the base metals"...I believe it would help your thought process to term the action of a sulfuric cell as "de-plating", in distinct contrast to the AP (not AR) process (now seemingly called "copper II chloride" process) used on fingers. In the AP process the copper underlying the gold contacts is dissolved and the remaining gold foils mechanically, physically detach from the board and are gathered. They (the foils) never stop being elemental gold. In the Sulfuric cell, gold is actually chemically dissolved away from the PINS. IME this difference in process is often unclear for newbs.


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## aptus (Dec 16, 2012)

Thank you both for replying. Regardless if one uses a sulfuric cell to deplate (which disolves the gold) or the AP process to dissolve the gold and the base metals, doesn`t the solution then needs to go through the Aqua-regina process (I call AR) to remove the forein base metals to obtain the purest gold possiable?


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## element47.5 (Dec 16, 2012)

No, this is the precise point I was trying for. The AP process DOES NOT dissolve gold. It undermines the copper that, however you wish to state it; is the foundation, the underlayment for the gold. It does this by dissolving the copper...when a PC board is mfd, the starting item is a board completely covered on one (or both) side(s) with copper. We then remove/etch the copper from where we DON'T want it. It is a subtractive process to make the board intended to hold the parts and to provide the current pathways to make something work. But we ADD gold (on top of the copper) on top of the fingers to provide a corrosion-resistant contact in use. Under the gold contact fingers then, is a layer of copper. Dissolve this, and the gold plated on top of the copper falls away, becomes detached from the board. *But the gold is not dissolved, in solution. It's more like it was mechanically scraped off. * It is as if you wished to remove a tile floor and you did it by somehow deteriorating or disintegrated the grout or the mastic that holds the tiles on. You are really not altering the nature of the tiles themselves. This is lots different than the sulfuric cell...where the gold goes into solution. And, one of the reasons why this approach is used is that the ratio of gold to base-metal in pins is large. We could theoretically dissolve the base metal out from under the gold plating in pins...but there would be vastly more base metal than gold, hence large chemical expense. Also, the composition of the pins is variable--can be lots of things, or at least several different things. And, it would be like hollowing out the Washington monument (obelisk) by tunneling up from the base. Not good surface area for chemical attack. 

My understanding is that the fallout or precipitate from the sulfuric cell, yes, has to go through an AR process to purify the Au. But here is where my own knowledge gets shaky, hence I will leave off. I just wanted to point out the essential difference between the two processes, because newbs encounter them both with their escrap and IME get them mixed up.


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## butcher (Dec 16, 2012)

We use several methods to separate the gold and the base metal, beside mechanical separation a few like de-plateing the gold in concentrated sulfuric acid cell, copper II chloride (acid/peroxide)leaf for thin copper, nitric acid, these remove the majority of the base metal from the gold, these are considered recovery processes.

The recovered gold although high percentage compared to base metals is still very impure.

Think of it like we wiped off most of the mud, and it looks better, but it is still pretty dirty and needs a good cleaning to shine, heck we might just have to give this a good scrubbing twice to make this baby shine.

The gold needs refining, this is where we put the gold into solution and separate insoluble substances, and precipitate out the gold as a much purer product of refined gold, many times gold need to be refined more than once for high purity.

Aqua regia (not aqua regina), HCl/NaClO (bleach), or other methods put gold into solution, we then us chemical fairly selective for gold to precipitate gold and leave these small traces of other metals in solution.

Too much base metals in a solution with our dissolved gold can make recovering our gold from that solution much more difficult, and will not produce gold of a very high quality, for this reason you only want to dissolve gold that you have previously removed as much base metal from as you can in a recovery step, before moving to the refining step of putting the gold into solution.


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## superten67 (Dec 17, 2012)

element47.5 said:


> No, this is the precise point I was trying for. The AP process DOES NOT dissolve gold. It undermines the copper that, however you wish to state it; is the foundation, the underlayment for the gold. It does this by dissolving the copper...when a PC board is mfd, the starting item is a board completely covered on one (or both) side(s) with copper. We then remove/etch the copper from where we DON'T want it. It is a subtractive process to make the board intended to hold the parts and to provide the current pathways to make something work. But we ADD gold (on top of the copper) on top of the fingers to provide a corrosion-resistant contact in use. Under the gold contact fingers then, is a layer of copper. Dissolve this, and the gold plated on top of the copper falls away, becomes detached from the board. *But the gold is not dissolved, in solution. It's more like it was mechanically scraped off. * It is as if you wished to remove a tile floor and you did it by somehow deteriorating or disintegrated the grout or the mastic that holds the tiles on. You are really not altering the nature of the tiles themselves. This is lots different than the sulfuric cell...where the gold goes into solution. And, one of the reasons why this approach is used is that the ratio of gold to base-metal in pins is large. We could theoretically dissolve the base metal out from under the gold plating in pins...but there would be vastly more base metal than gold, hence large chemical expense. Also, the composition of the pins is variable--can be lots of things, or at least several different things. And, it would be like hollowing out the Washington monument (obelisk) by tunneling up from the base. Not good surface area for chemical attack.
> 
> My understanding is that the fallout or precipitate from the sulfuric cell, yes, has to go through an AR process to purify the Au. But here is where my own knowledge gets shaky, hence I will leave off. I just wanted to point out the essential difference between the two processes, because newbs encounter them both with their escrap and IME get them mixed up.



id just like to join in for a minute here as ive had problems as a few of you will know as butcher amongst others has given me advice.
i am also by no means an expert but just wanted to add in an ideal world the gold floats and the copper dissolves.....but not allways as if the acid peroxide mix gets too reactive(on the peroxide side of it)the mix WILL dissolve gold.
then you will have the same black powder you find in the deplating cells which then has to be redisolved and cleaned up again.
i had this problem when having used 9% peroxide and following the 2:1 ratio which was not a good idea.


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## Gratilla (Dec 17, 2012)

aptus said:


> The links provided in replies to my previous question were very helpful. May I be doing something wrong when I use the search as everytime I enter something in it it says nothing found. I tried basic searches such as HCI and SMB with the same results.



Unfortunately the forum Search function ignores words of less than FOUR characters. A mini blot on an otherwise excellent forum. (IMO)


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## g_axelsson (Dec 17, 2012)

A tip is to use the "*site:goldrefiningforum.com*" in a google search combined with whatever you are searching for, for example SMB.
Like this https://www.google.com/search?q=site%3Agoldrefiningforum.com+SMB

/Göran


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## Gratilla (Dec 17, 2012)

Thanks Göran, it works. But it doesn't return nearly all the hits.

Gotta look at the "glass half full" though! :mrgreen:


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## g_axelsson (Dec 17, 2012)

1860 pages where SMB is mentioned isn't enough?
Which hits are you lacking?

You surely have a large glass. :shock: 

/Göran


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## Gratilla (Dec 17, 2012)

Erm, I was testing with SSN. A much smaller glass with only 7 (non-unique) hits. I know there are a lot more.


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## g_axelsson (Dec 17, 2012)

That's strange. I get 70 hits on SSN (Google claims 155 at first).

https://www.google.com/search?q=site%3Agoldrefiningforum.com+SSN

/Göran


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## Gratilla (Dec 17, 2012)

Wow, you're right. <Now, what did I do wrong? <rhetorical>>

Thanks.


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## aptus (Dec 24, 2012)

I made my lead that goes into the sulfuric acid have five fingers instead of one single piece. I hooked the black or negitive lead from the charger to it and hooked the red or positive cable to the coppper basket that contained the gold platted pins. To my surprise the lead piece was gold colored and it appeared that I gold plated the lead piece. So I switched the terminals around putting the red or positive on the red and the black or negitive on the copper basket. The gold platting that was on the lead did seem to come off and go into the solution but it appeared more grey in the solution than black as it was the first time when the gold was coming off the pins.

Obviously I had the pos and neg clamps turned around

1.Is the greyish color in the solution ok to keep using or do I need to dump it and startr over?

2.Should I use just a solid piece of lead rather than the five finger piece I made?

3. What if I was to do it back ward as I was thus putting all the gold on the lead and then switch the terminals around correctly to remove it from the lead?

Yes or no is fine if time doesn`t allow for a move definative answer. Thanks in advance.


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## butcher (Dec 25, 2012)

You can test your power supply for polarity, or if the power supply had a shorted diode you would deliver alternating current to the cell.

Get a diode from a circuit board 3 amp diode will do here, it will be a black device with a white stripe on one end, the white stripe end is the cathode of the diode the other end is the diodes anode, current will only flow from anode to cathode in a diagram it will look like an arrow with a line:
(Anode --->I-- cathode)
Hook the diode to a 12-volt automotive tail lamp in series the (O) here will represent lamp:
( --->I---O----)
The current will flow from (+ to -) or anode to cathode through the diode but not backwards from (- to +)
So the light bulb will only light up when your Direct current power supply positive is hook on the back of the diode (side without stripe) and your power supply negative is hooked to the lamp wire:
(pos +--->I---O--_ Neg) if the bulb light when the power supply leads are reversed you have a sorted diode in the power supply or it is making alternating current.

If you have a digital voltmeter you can use it instead of the diode and lamp, the voltage will read on the DC scale the polarity (with red meter lead in V and black lead in COM, the red test probe to power supply positive, black meter lead to power supply negative will read voltage, if meter leads are hooked up backwards the meter will have a - negative symbol in front of voltage reading, you can also switch the meter to read AC voltage to see if your power supply maybe has a shorted diode and putting out alternating current.


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## Harvester3 (Jan 1, 2013)

element47.5 said:


> No, this is the precise point I was trying for. The AP process DOES NOT dissolve gold. It undermines the copper that, however you wish to state it; is the foundation, the underlayment for the gold. It does this by dissolving the copper...when a PC board is mfd, the starting item is a board completely covered on one (or both) side(s) with copper. We then remove/etch the copper from where we DON'T want it. It is a subtractive process to make the board intended to hold the parts and to provide the current pathways to make something work. But we ADD gold (on top of the copper) on top of the fingers to provide a corrosion-resistant contact in use. Under the gold contact fingers then, is a layer of copper. Dissolve this, and the gold plated on top of the copper falls away, becomes detached from the board. *But the gold is not dissolved, in solution. It's more like it was mechanically scraped off. * It is as if you wished to remove a tile floor and you did it by somehow deteriorating or disintegrated the grout or the mastic that holds the tiles on. You are really not altering the nature of the tiles themselves. This is lots different than the sulfuric cell...where the gold goes into solution. And, one of the reasons why this approach is used is that the ratio of gold to base-metal in pins is large. We could theoretically dissolve the base metal out from under the gold plating in pins...but there would be vastly more base metal than gold, hence large chemical expense. Also, the composition of the pins is variable--can be lots of things, or at least several different things. And, it would be like hollowing out the Washington monument (obelisk) by tunneling up from the base. Not good surface area for chemical attack.
> 
> My understanding is that the fallout or precipitate from the sulfuric cell, yes, has to go through an AR process to purify the Au. But here is where my own knowledge gets shaky, hence I will leave off. I just wanted to point out the essential difference between the two processes, because newbs encounter them both with their escrap and IME get them mixed up.



Very well stated friend


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