Micro stripping cell

Since my quantities of gold bearing materials are very limited and I don't want to end up with a lot of waste to figure out what to do with, I decided to make a miniature version of LaserSteve's sulfuric stripping cell.

What I did was use a small glass candle holder that I got from the Dollar store and a lead cathode that I had made several years ago when I first joined this forum but never used. The cathode was bent over the edge of the square glass container and I added around a half a cup of concentrated sulfuric acid (Liquid Fire drain cleaner).

With my very small pile of gold plated pins and wires I processed them in this micro sized device one by one until I was left with only the ones that didn't have enough non-plated sections left to grip with the alligator clip. These will have to wait until I have enough to buy a piece of copper mesh from Steve.

Each pin only took between a second and maybe a few seconds to completely strip. I am happy I didn't try processing them in AP which would have taken longer and produced much more waste. My sulfuric acid is very dark now but I expect it to clear back up as the gold settles out. It will be a long time before I have enough powder to worry about recovering the gold but now I know the process works and will slowly gather up more material to run through the cell. In the meantime, I only have the half cup of acid to store instead of jars or buckets of used AP.

I used a variable voltage/current power supply I had from a plating project which has a maximum current of 3 amps. For this small cell that was plenty. I didn't try it but I think even a cheap wall wart type power supply would have worked or the normal car battery charger. Doing 1 pin at a time I never went over 1 amp and most only took 10-30 mA for the second or two it was deplating.

I'm not saying everyone should start this small but for the many beginners like me with limited materials to process this seems to work. You wouldn't want to run pounds of pins at a time in such a small cell but for a test device I'm happy with how it turned out. It may be all I ever need unless this becomes more than just a hobby/learning experience.

My candle holder didn't come with a cover so I plan to store my used acid in a jar and the lead cathode in another one with distilled water. You might notice that I had my micro cell in a plastic gold pan just in case anything spilled. It didn't but better safe than sorry. Concentrated sulfuric acid is some scary stuff and now it has a little gold powder in it so I don't want it to get away IF something goes wrong. I know nobody likes being told over and over but BE CAREFUL.

Thanks LaserSteve and everyone on this forum. I can't believe I waited this long to try the stripping cell.

I believe the temperature could get faster out of control with this tiny amount of sulfuric, maybe a glass thermometer would serve well. Just a thought. I at least feel better having an eye at the termperature.

I like it! Can you give us an idea of the size of your little candle holder? There's nothing there to compare it's size to.

Dave

Sorry about not mentioning any dimensions. The candle holder is around 2-3/4" (close to 7 cm for the metric readers) square at the top and 3" (~7.5 cm) high.



I haven't used it long enough to raise the temperature any noticeable amount. If I can find a stick-on thermometer that sounds like a good idea especially IF I ever try using a copper mesh basket.

You should be able to see from this picture that the acid did get much darker. I'm still waiting for it to settle out but I'm thinking about ripping another board apart and get a few more pins to run through it before I put it away. Most of what I had were from plastic connectors and took some time to get to the pins but that's where the majority came from. The little plated fingers that made contact with a card (like a credit card) seemed to have the most gold on them but there was only 6 or 8 of those on each board I got to scrap. Some came from an old CD drive also. There's not a lot in each device but they should eventually add up if I keep at it.

Cut off all silver coloured parts, only use fully goldplated, - that may save some time and make it more effective. I guess you need at least to run 100-200g of this lowgrade stuff (even if close cut) to get a noticable amount of gold. A noticable amount would start with 0,3g from my point of view.

solar_plasma said:

Cut off all silver coloured parts, only use fully goldplated

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Since he's only stripping one pin at a time, leaving the non gold plated portion gives him a place to attach his alligator clip without having to dip the clip into the acid.

Dave

solar_plasma said:

Cut off all silver coloured parts, only use fully goldplated, - that may save some time and make it more effective. I guess you need at least to run 100-200g of this lowgrade stuff (even if close cut) to get a noticable amount of gold. A noticable amount would start with 0,3g from my point of view.

Click to expand...

I was purposely leaving as much silver colored part on each pin so I had something to grip with the alligator clip. I didn't want to dip the clip in the acid. If/when I switch to a copper mesh basket I can cut the pins down smaller to leave mostly gold plated parts. Looks like I've got a long ways to go before I get any amount of powder. I didn't weigh my pins before running them but I'd guess I ran a gram or two so far. Eventually I'll get enough to try to melt it into a tiny button. So far all of my experiments have been small scale and I don't have enough to try melting yet. I'm assuming that the powder from this cell will still need refined to make sure there isn't any copper or nickel in it.

Good post1 I have been using a 12oz pyrex beaker for my cell,which is nearly the same dimensions(except round of course). I use a fixed 5 volt dc power supply, 2" wide lead strip on one side and it works super. I have done a lot of larger pins and connector pins with this and it takes almost an hour to get warm enough(40 deg. C for me).I let it cool and go do something else for a half hour. i could set a second one up and alternate them,but I have plenty of other things to do.

I am working on a cell now with a dish similar to lasersteves, but the dish is only two cups. It came with a lid from WalMart for just under $4. I have another container that is 4x4 and 5 1/2 inches deep. I have everything ready except the power supply. I do like that micro cell for some of the lower grade pins though. The long ones with just a tip of plating to them should be fairly easy in a cell that small. Any more information on your power supply? Keep us informed, I am very interested in it.

Edit: I like the effort to your experiment!

The power supply I used is a (HY1503D) like the one on this site:

http://toolboom.com/en/DC-Power-Supply-LCD-display-0-15V-0-3A-HYelec-HY1503D.php

Mine came with a nickel plating class I took. I don't think you really need this type of power supply but I had it so I'm using it. One benefit to this type of regulated power supply is I can set the voltage or the current to whatever I want up to the 3 Amp limit. For my first try with my cell I just set it to 12 volts and the current depended on how much gold was being de-plated. One pin at a time I never seen it go above 1 Amp. I'm sure the power as well as the heat will go up when I do more quantity at a time with a copper mesh basket.

I did gather up a few more pins to run through this little cell but I haven't done any more yet. I'm waiting until I have more before setting it back up. I put the acid into a sealed jar to keep it from absorbing water from the air although being winter here, there isn't much humidity in the air. I did notice that the small amount of gold (black powder) I got from the small amount of pins run so far did NOT settle out. Shouldn't matter since there isn't much gold in it yet. I'll just keep using it until it gets full or gets diluted and starts dissolving copper before worrying about recovering the gold.

I know this is not a large cell but it has encouraged me to work on mine. After beating my head against a wall all morning, I have a power supply almost ready. Need to pick up a few minor parts tomorrow and should be good for a test run. I happened to remember a power supply for a computer I bought years ago and never used. It turned out to be one that uses the fan for the load resistor. If the test goes well, I have a dozen or so mother boards that need stripping along with 30+ hard drives and floppy drives. I already have almost 500 grams of pins already to go.

edit: If you PM me your info, I will send you a piece of copper mesh for the encouragement.

sharkhook said:

I know this is not a large cell but it has encouraged me to work on mine. After beating my head against a wall all morning, I have a power supply almost ready. Need to pick up a few minor parts tomorrow and should be good for a test run. I happened to remember a power supply for a computer I bought years ago and never used. It turned out to be one that uses the fan for the load resistor. If the test goes well, I have a dozen or so mother boards that need stripping along with 30+ hard drives and floppy drives. I already have almost 500 grams of pins already to go.

edit: If you PM me your info, I will send you a piece of copper mesh for the encouragement.

Click to expand...

I ran some more pins through my tiny cell and am still impressed with how quick the gold is removed from the parts. I guess that means there is very little gold on them to start with but I'm really glad I am using this method instead of trying to dissolve the base metals all away from the tiny bit of gold.

I also put a small, stick-on-thermometer on the outside of my little cell. Doing one pin at a time I can't imagine it is ever going to heat up but it might when I try the mesh basket and more quantity at a time. You might want to use a larger version if you plan to do much quantity quickly. This mini cell is a good way to test the process at least for me. As I said, this might be all I need and I don't plan on building a larger one unless I get a lot more material to process.

Thanks for the offer of the copper mesh but another member already offered me a piece. I'll post more pictures of my mini cell with the basket once I get the mesh and get it built. I am still saving up the pins that don't have enough non-plated parts to grip with the alligator clip so I should have some to test the basket with.

I am going to use the container I have with 1 1/2 to 1 3/4 cup of acid. That will leave me a bit of room for a small basket and reduce the chance of a spill or over flow. I don't plan on running a very large basket. I hope to do a gram or two at a time. Like you I am in no rush to produce quantity, just get a basic idea of the overall process. I will try to add some pictures when I get it going. The cold here should be out by this evening and I have to get caught up on some work outside so it may be a few days yet.

I got a piece of copper mesh from a forum member who also send some hi grade pins for me to try. Edited to say THANKS Eric (etack) - I didn't want to mention his name until I knew he was OK with it. I quickly folded up a tiny basket for my tiny cell and tested it out to strip more than one pin at a time. This will be especially helpful where there isn't enough non-plated part left to grip with the alligator clip.











This new basket seems to work real good. I did have to stir or shake the basket some to get all the parts to strip. I also adjusted my power supply setting the current to a maximum of 1 amp and turning the voltage up all the way. That way the current stays at or below 1 amp which should help keep from over heating the acid as well as not maxing out the power supply all the time. I could have just switched to a car battery charger but I already had this power supply ready to go. It was a little slower than it could have been with more power but still way faster than one pin at a time like I had been doing.

The black powder (gold) did settle out of the acid but it took a couple days without moving the container. Now it is all mixed back in since I used it again. There wasn't much but there was some powder on the bottom that I could see with a flashlight through the cleared acid. Now that I ran several small batches with the basket, there should be much more gold in the cell . This is going to take a while to get enough to move on to the next step but I'm getting there.

That way the current stays at or below 1 amp which should help keep from over heating to acid

Click to expand...

just remember P=I*U

solar_plasma said:

That way the current stays at or below 1 amp which should help keep from over heating to acid

Click to expand...

just remember P=I*U

Click to expand...

My power supply automatically adjusts the voltage up to the limit of 15 volts to try to keep the current at the 1 amp that I set. It changes pretty fast but I think the voltage started out 6 or 7 volts with the current at 1 amp and then quickly adjusts to the maximum 15 volts as the current goes down. I'll probably get this wrong but I think the resistance must start low and then gets higher as the gold is removed and the base metal is exposed. I watch and when the current gets to zero, I stir the parts and that usually gets it started again until there is no gold left and the current stays at zero. I'm going to guess that this is similar to anodising the base metal. I once worked for a company that anodised aluminum parts but I wasn't directly involved with the anodising process. I think they used sulfuric acid but I doubt it was concentrated acid. In fact I'm sure it wasn't concentrated acid.

I'll probably get this wrong but I think the resistance must start low and then gets higher as the gold is removed and the base metal is exposed. I watch and when the current gets to zero, I stir the parts and that usually gets it started again until there is no gold left and the current stays at zero.

Click to expand...

That's correct, I would say.

P_max=1A*15V=15W .... I just wanted to express, that 15W could make a little amount of liquid pretty warm...just to keep in mind, not leaving it alone.

Nice little setup!

Very Nice! I hope to work on mine later this evening. I am getting there slowly, but getting there.

For the smaller clips, you can find them at Radio Shack made of copper. A 10 pack here was under $4.

Some of those are just plated copper, not solid. FYI

Yes, be sure to get the all copper ones. I had to ask the guy twice just to get him away from the plated ones. He had a funny look on his face when I told him the plated ones didn't play well with acid.