Glycerin
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Has anyone ever tried this without glycerin? Someone should try it. If it doesn't work without it, you can always add it. I used the sulfuric stripper, on a grand scale (up to 500 gallons), for 30 years, without any glycerin.
Noxx
Well-known member
I think it's used to reduce the water surface tension. This way, gold does not float. Or maybe it's something else ?
I figure it was used to prevent the corrosion of the alligator clips or splashing. The gold should sink anyway regardless of the surface tension right? I Noxx's point of view because there are no chemical reaction between the Sulfuric acid and Glycerin. I hope Steve reads this, I know he can shed some light on this subject.
I've stated this many times before, but it bears repeating.
The original recipie that I have called for a small amount of glycerin (1/16 teaspoon = 0.31 mL ) per cup ( 236.6 mL ) of concentrated sulfuric acid.
The recipie did not explain what the purpose of the glycerin was, but I used it to follow the recipie.
I have tried the cell with straight concentrated sulfuric acid and it works.
Steve
The original recipie that I have called for a small amount of glycerin (1/16 teaspoon = 0.31 mL ) per cup ( 236.6 mL ) of concentrated sulfuric acid.
The recipie did not explain what the purpose of the glycerin was, but I used it to follow the recipie.
I have tried the cell with straight concentrated sulfuric acid and it works.
Steve
eagle2
Well-known member
Noxx said:
eagle2
Well-known member
eagle2 said:
eagle2
Well-known member
Glycerin as an additive is used to reduce the ionic tension at the cathode. This results in a denser more adherent plate of the metal that happens to be in the electrolyte onto the cathode. There are many better additives, but usually they are proprietary. The better plating action supposedly keeps more of the base metal off the bottom where the gold is. My electro-winning cell for gold plate uses sulfuric acid about 4 molar with distilled water, some glycerin and a surfactant called triton x-100. I have a power supply that needs to be limited to about 10 amps, so it has two ohms of resistance in series in circuit. Never-the-less I can strip the plate off a large object in about 5-10 minutes. This is still a tedious business and I don`t use it much. Also, the electrolyte always gets overloaded with base metal sulfates too quickly, no matter how quick you are with changing anodes. I am very thankful for finding this site with the tips and huge amounts of priceless info. Thank you all! And by the way never use an additive in a silver nitrate - silver recovery cell, because you want to easily scrap the coating off the SS cathode.
So Eagle. You're saying that glycerin will help copper or nickel stick better to a cathode.
But in a de-plating cell, with a lead anode, nothing seems to go onto the lead anyways.
Do I dare add glycerin to my copper & nickel plating tanks?
What do you think of this GSP?
But in a de-plating cell, with a lead anode, nothing seems to go onto the lead anyways.
Do I dare add glycerin to my copper & nickel plating tanks?
What do you think of this GSP?
eagle2
Well-known member
Hi Phillip. I think you mean the cathode. That`s where the plating takes place. There was a guy named jason on e-bay selling info and setup materials for a electrowinning-cell. He used concentrated sulfuric or battery acid and a lead cathode. You have to use lead, it holds up in strong sulfuric. I bet most got this recipe there or passed it on from one to another.
It`s unnecessary and dangerous to use strong concentrations of acid. you always get fume and spray. He ran the battery charger wide open. You still get all the current you could use with dilute solutions. To get a good plate you want to watch the current density. that means running the cell at 2-3 volts from cathode to anode. I`m not into additives, but I think you can find a lot of info on just googleing keywords. To just strip gold plate you can run a higher voltage, but protect yourself from the fume. I use a copper cathode, and get sticking. But still scrape any black residue off it. Your always going to get copper mixed in with the gold. I don`t melt, but always use chemical separations.
Sorry, I don`t know what GSP is? --- Al
It`s unnecessary and dangerous to use strong concentrations of acid. you always get fume and spray. He ran the battery charger wide open. You still get all the current you could use with dilute solutions. To get a good plate you want to watch the current density. that means running the cell at 2-3 volts from cathode to anode. I`m not into additives, but I think you can find a lot of info on just googleing keywords. To just strip gold plate you can run a higher voltage, but protect yourself from the fume. I use a copper cathode, and get sticking. But still scrape any black residue off it. Your always going to get copper mixed in with the gold. I don`t melt, but always use chemical separations.
Sorry, I don`t know what GSP is? --- Al
Eagle said:
That guy started selling cell plans modeled after Loren's. I bought Loren's plans a full year before Jason ever started selling electrolytic cell plans on ebay. Jason's first auctions actually used Loren's ebay photo for his cell plans auction until Loren called him on it.
All that being said, there are so many variations of the cell, and the electrolytic cell has been around longer than any of us.
Steve
I started using the sulfuric cell in 1971. I first set up a 50 gallon tank. I used the same solution every day, without replacing it, for about 2 years. About the only common metal that will foul the solution is nickel.
eagle2
Well-known member
Hi Steve. Thank you for the info. I never met Lorens, But yes the E-cell has been around a long time with large variations. I even read a scientific article describing some aspect of electro-refining and the author said its yet more of an art than fully laid out science.
Hello Goldsilverpro! My Cell is a glass 3 gallon fish tank. When I tried stripping small gold plated objects such as pins and small flat pieces, the gold came off unevenly. If I waited till all the gold was off I knew a lot of copper was going into solution and on the bottom. Also, much gold plate has a plate of nickel over the copper base, then the gold plate. After about 30-40 hours the current flow drops off. Cleaned out the cell and put the electrolyte back in. I then use a carbon anode to plate out the base metals in solution and reuse it again. Now if I use it that way, its only for large objects.
You say that you didn`t hardly ever clean out the solution. What did you have for anodes? Did you use 50 gallons of concentrated sulfuric?
Al
Hello Goldsilverpro! My Cell is a glass 3 gallon fish tank. When I tried stripping small gold plated objects such as pins and small flat pieces, the gold came off unevenly. If I waited till all the gold was off I knew a lot of copper was going into solution and on the bottom. Also, much gold plate has a plate of nickel over the copper base, then the gold plate. After about 30-40 hours the current flow drops off. Cleaned out the cell and put the electrolyte back in. I then use a carbon anode to plate out the base metals in solution and reuse it again. Now if I use it that way, its only for large objects.
You say that you didn`t hardly ever clean out the solution. What did you have for anodes? Did you use 50 gallons of concentrated sulfuric?
Al
PhillipJ,
Somewhere, I have read of glycerin being used as a grain refiner for certain plating baths. However, I certainly wouldn't add any of it to your nickel or copper baths unless the original formula called for it, which is very doubtful. Plating formulas are pretty much carved in stone and it's best not to tinker with them. Plating success depends on following the original formula to a T and keeping the ingredients well within the suggested ranges. To do this right, you really need to be set up to analyze the bath ingredients.
eagle2,
I'm GSP
Welcome to the forum. I shouldn't rub it in to a Kansan, but I sure liked the outcome of the MU/KU football game Saturday night. It got pretty scary at the end, though. And now, Mizzou is #1 in the polls! I thought I'd never see that in my lifetime. Go Tigers.
I covered my version of the sulfuric process in this thread:
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=226
I think you're making a mistake by using weak sulfuric. As I understand it, you're using 4 Molar, which is only 20-25% sulfuric. This is why you're having problems with the copper dissolving and plating out. The stronger the sulfuric, the less copper (or, anything else) will dissolve.
I always used concentrated (~96%, by weight) technical grade sulfuric with about 5% to 10% water, by volume, added (add the acid to the water!!). You need a little water to perk up the speed. A 10% water addition, by volume, is equivalent to about a 5% addition, by weight, since the sulfuric is almost twice as heavy as water. Conc. sulfuric can be used without the water but, a little water will speed it up. If you're in a humid climate, only use 5% water as the sulfuric will absorb water from the air.
I daily stripped the gold and gold braze from reject, sealed, side-braze CPU packages in this system, at the rate of about 50,000 to 100,000 of them per week. This was a commercial venture. I mounted them on bare brass or copper racks, using piano wire spring contacts to hold the parts. There was little or no attack on any part of the rack, tank, or other portions of the packages, when using the strong sulfuric (it was slightly modified - my invention - in order to strip the brazes). I then re-plated the packages and returned them to the customer for re-use - Intel, AMD, and AMI were my biggest customers. We basically recycled their reject parts, for re-use, and charged them half the cost of a new package. Since most of the gold value was in the brazes used on the chip and the sealing lid, we removed much more gold than we put back on. The extra gold recovered essentially paid for the process.
I used a 50 gallon welded mild steel tank and made the tank the cathode. After using it daily, at room temp, for about 2 years, there was hardly any visible attack on the tank, except a little at the solution surface, where the acid, the steel, and the oxygen in the air all met. Don't use stainless - it will be slowly eroded, due to the presence of the Cr and Ni. Nickel (and probably cobalt) is the bad actor in this system. If too much is dissolved, it will stop the action. I have thought about adding a little potassium dichromate to the sulfuric to inhibit the attack on the nickel, but I've never actually tried it.
Your use of a glass fish tank is scary. I sure wouldn't want 4 gallons of sulfuric in my lap. If you go to the strong sulfuric that I suggest, you must go to a steel tank because it will likely attack the cement that holds the glass tank together. Search around a scrap yard and you will find some sort of mild steel container that is just the right size and shape for what you need - cheap. I would try to find a container that is at least 1/8" thick.
When using the stronger sulfuric, you will get far less fizzing than you will with a weaker solution. The trick is to start the rectifier at zero and slowly crank it up. At first, the amps are high and the volts are low. After about a minute, the amps will drop, somewhat, and the voltage will increase. As you slowly crank up the voltage, the amps will first increase and then will decrease. At some point, when the gold is completely stripped, the volts will be at about 9 (or, higher, if desired) and the amps will be zero. At this point, all of the gold is stripped. This won't work with a more dilute sulfuric because it will continue to attack the base metals and will therefore continue to draw current.
With the stronger sulfuric, nothing deposits on the cathode (the mild steel tank). The gold forms as a powder and settles to the bottom. The solution is then drained off and the gold is easily recovered and then refined in aqua regia.
I might mention, eagle2, that there's a hell of a lot of difference in concentrated sulfuric (96%+) and battery acid (about 40%) in this system. The battery acid will dissolve almost everything. Conc. sulfuric, with a little water, will only essentially dissolve and precipitate the gold. There will only be very minor amounts of base metals in the gold sludge.
When using the conc. sulfuric with only 5-10% water, by volume, regular gold plating will completely be removed in a minute or two. Sure beats 30-40 hours. With my modification to the solution, the gold brazes took about 15-20 minutes.
I've only dented the surface of this subject. I have maybe 20 years experience of working daily with this solution on a grand scale. I'm game, if you want to go deeper into this.
TERMS: My definitions. There are variations but these give the general idea.
Electrowinning. The electrodeposition of metals that have already been put into solution before the solution is put into the electrowinning tank. Uses an inert anode. Pure metal deposits on cathode. Impurities remain in the solution.
Electrorefining. Electrolytically dissolves an impure anode and simultaneously deposits pure metal at the cathode. Those impurities that dissolve remain in the solution. Those that don't dissolve are usually collected in an anode bag.
Electrostripping. Selectively removing a metallic coating, electrolytically. The dissolved metal either plates onto the cathode or immediately precipitates out, as in the gold/sulfuric system, above.
Somewhere, I have read of glycerin being used as a grain refiner for certain plating baths. However, I certainly wouldn't add any of it to your nickel or copper baths unless the original formula called for it, which is very doubtful. Plating formulas are pretty much carved in stone and it's best not to tinker with them. Plating success depends on following the original formula to a T and keeping the ingredients well within the suggested ranges. To do this right, you really need to be set up to analyze the bath ingredients.
eagle2,
I'm GSP
Welcome to the forum. I shouldn't rub it in to a Kansan, but I sure liked the outcome of the MU/KU football game Saturday night. It got pretty scary at the end, though. And now, Mizzou is #1 in the polls! I thought I'd never see that in my lifetime. Go Tigers.
I covered my version of the sulfuric process in this thread:
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=226
I think you're making a mistake by using weak sulfuric. As I understand it, you're using 4 Molar, which is only 20-25% sulfuric. This is why you're having problems with the copper dissolving and plating out. The stronger the sulfuric, the less copper (or, anything else) will dissolve.
I always used concentrated (~96%, by weight) technical grade sulfuric with about 5% to 10% water, by volume, added (add the acid to the water!!). You need a little water to perk up the speed. A 10% water addition, by volume, is equivalent to about a 5% addition, by weight, since the sulfuric is almost twice as heavy as water. Conc. sulfuric can be used without the water but, a little water will speed it up. If you're in a humid climate, only use 5% water as the sulfuric will absorb water from the air.
I daily stripped the gold and gold braze from reject, sealed, side-braze CPU packages in this system, at the rate of about 50,000 to 100,000 of them per week. This was a commercial venture. I mounted them on bare brass or copper racks, using piano wire spring contacts to hold the parts. There was little or no attack on any part of the rack, tank, or other portions of the packages, when using the strong sulfuric (it was slightly modified - my invention - in order to strip the brazes). I then re-plated the packages and returned them to the customer for re-use - Intel, AMD, and AMI were my biggest customers. We basically recycled their reject parts, for re-use, and charged them half the cost of a new package. Since most of the gold value was in the brazes used on the chip and the sealing lid, we removed much more gold than we put back on. The extra gold recovered essentially paid for the process.
I used a 50 gallon welded mild steel tank and made the tank the cathode. After using it daily, at room temp, for about 2 years, there was hardly any visible attack on the tank, except a little at the solution surface, where the acid, the steel, and the oxygen in the air all met. Don't use stainless - it will be slowly eroded, due to the presence of the Cr and Ni. Nickel (and probably cobalt) is the bad actor in this system. If too much is dissolved, it will stop the action. I have thought about adding a little potassium dichromate to the sulfuric to inhibit the attack on the nickel, but I've never actually tried it.
Your use of a glass fish tank is scary. I sure wouldn't want 4 gallons of sulfuric in my lap. If you go to the strong sulfuric that I suggest, you must go to a steel tank because it will likely attack the cement that holds the glass tank together. Search around a scrap yard and you will find some sort of mild steel container that is just the right size and shape for what you need - cheap. I would try to find a container that is at least 1/8" thick.
When using the stronger sulfuric, you will get far less fizzing than you will with a weaker solution. The trick is to start the rectifier at zero and slowly crank it up. At first, the amps are high and the volts are low. After about a minute, the amps will drop, somewhat, and the voltage will increase. As you slowly crank up the voltage, the amps will first increase and then will decrease. At some point, when the gold is completely stripped, the volts will be at about 9 (or, higher, if desired) and the amps will be zero. At this point, all of the gold is stripped. This won't work with a more dilute sulfuric because it will continue to attack the base metals and will therefore continue to draw current.
With the stronger sulfuric, nothing deposits on the cathode (the mild steel tank). The gold forms as a powder and settles to the bottom. The solution is then drained off and the gold is easily recovered and then refined in aqua regia.
I might mention, eagle2, that there's a hell of a lot of difference in concentrated sulfuric (96%+) and battery acid (about 40%) in this system. The battery acid will dissolve almost everything. Conc. sulfuric, with a little water, will only essentially dissolve and precipitate the gold. There will only be very minor amounts of base metals in the gold sludge.
When using the conc. sulfuric with only 5-10% water, by volume, regular gold plating will completely be removed in a minute or two. Sure beats 30-40 hours. With my modification to the solution, the gold brazes took about 15-20 minutes.
I've only dented the surface of this subject. I have maybe 20 years experience of working daily with this solution on a grand scale. I'm game, if you want to go deeper into this.
TERMS: My definitions. There are variations but these give the general idea.
Electrowinning. The electrodeposition of metals that have already been put into solution before the solution is put into the electrowinning tank. Uses an inert anode. Pure metal deposits on cathode. Impurities remain in the solution.
Electrorefining. Electrolytically dissolves an impure anode and simultaneously deposits pure metal at the cathode. Those impurities that dissolve remain in the solution. Those that don't dissolve are usually collected in an anode bag.
Electrostripping. Selectively removing a metallic coating, electrolytically. The dissolved metal either plates onto the cathode or immediately precipitates out, as in the gold/sulfuric system, above.
aflacglobal
Well-known member
Great piece Chris. :wink: :wink: :wink:
I take it the extra addition of the H2O is the oxidizer that drives the reactions you don't want to happen.
Word of caution :!: :!: :!: Chris is correct about the acid affecting the glue. I ran a little experiment. I went to Lowe's and cut a sample of all their hoses and then got plexi glass, Lucite, and other items to experiment with.
I also tried a small fish tank. Wrong. :shock:
My work top has a box made out of 2 x 6's and lined with a pool liner for just that occasion. Please watch it. I have gotten one or two spits of acid on me. That's all i need of that. :?
I won't go into all the details. It is a little something i have been working on for awhile now. If you want to remove the base metals you should be able to do so by chilling the acid. I have a cooling compressor from a water fountain. I use a pump to circulate the water thru a series of glass tubes that surround the tubes that the acid runs thru after it leaves the stripping tank. The acid is then returned back to the tank to do its work again. It's modeled after a commercial method for etching boards.
I'm not using it in a reverse stripping cell though. I'm using it to strip copper from items. It's been kind of placed on hold while i chase the Barrick thing. I will pick it back up after the first of the year hopefully.
I take it the extra addition of the H2O is the oxidizer that drives the reactions you don't want to happen.
Word of caution :!: :!: :!: Chris is correct about the acid affecting the glue. I ran a little experiment. I went to Lowe's and cut a sample of all their hoses and then got plexi glass, Lucite, and other items to experiment with.
I also tried a small fish tank. Wrong. :shock:
My work top has a box made out of 2 x 6's and lined with a pool liner for just that occasion. Please watch it. I have gotten one or two spits of acid on me. That's all i need of that. :?
I won't go into all the details. It is a little something i have been working on for awhile now. If you want to remove the base metals you should be able to do so by chilling the acid. I have a cooling compressor from a water fountain. I use a pump to circulate the water thru a series of glass tubes that surround the tubes that the acid runs thru after it leaves the stripping tank. The acid is then returned back to the tank to do its work again. It's modeled after a commercial method for etching boards.
I'm not using it in a reverse stripping cell though. I'm using it to strip copper from items. It's been kind of placed on hold while i chase the Barrick thing. I will pick it back up after the first of the year hopefully.
eagle2
Well-known member
Hi GSP; Thank You for all those tips. Well taken.
Kansas will come back next year, you were lucky.
First my fish tank cell is close to three gallons. It is all glass, no seams. Has a plastic cover, I feel very safe with it. I can still do a limited amount of warming.
Also, I can strip the gold plate in a few minutes, my solution has to cleaned in about 30-40 hours of use, because the current has dropped off and the cathode is full of deposits.
I am looking at my Merck Index, It has basic characteristics of most common chemicals. It states: Copper very slowly attacked by cold Hcl or dilute sulfuric acid; readily by dilute nitric acid and by both hot concd H2SO4 and HBr.
Iron: Readily attacked by dilute mineral acids and attacked or dissolved, by organic acids; not appreciably attacked by cold concd H2SO4 or HNO3, but is attacked by the hot acids.
Nickel: Slowly attacked by dilute HCl or H2SO4; readily attacked by nitric acid (I found Nickel would not dissolve well in nitric unless I heated it).
(Dosn`t state what concd H2SO4 would do to nickel.)
I take it then that you had to keep your tank and solution from getting hot.
I have read electro stripping articles that describe the stripping action on gold plate or bullion. The gold never goes into solution in sulfuric. The underlying base metal is attacked through microscopic imperfections in the gold plate. These metals oxidize and go into solution. This loosens and breaks up the gold plate into fine bits. You can see the yellow glitter falling or floating. Some of its black. (thats why I like to use that Triton x-100 surfactant).
In the case where you have gold brazes or kt gold, the gold will be so fine that you see a black mud. And here the base metals have to go into solution or plate out; or if the solution is overloaded fall to the bottom with the gold .
That 10% water you mixed with the sulfuric acid provided a place where the base metals could go into solution. The metal sulfates are ionized here and this increases the current flow. I think concentrated sulfuric does not ionize as well as dilute sulfuric.
I think it all depends on what your anode is made of, which helps you decide how to run the cell. Temperature also figures.
It does take a lot of experience!
I`m going to try concentrated sulfuric in the cell with some CPU`s I have (10% water!). That was a great tip on the fact that CPU pins are electrically connected. I can hang them by one pin and zap em! The pins are magnetic and must be some flexible alloy of iron and cobalt. I had a previous tedious separation with ferric leach and a AR procedure with CPU`s. I had to get rid of a lot of ferric before I could precip the gold. This should be much easier.
Thanks to everybody for all your comments, much appreciated.
------- Al
Kansas will come back next year, you were lucky.
First my fish tank cell is close to three gallons. It is all glass, no seams. Has a plastic cover, I feel very safe with it. I can still do a limited amount of warming.
Also, I can strip the gold plate in a few minutes, my solution has to cleaned in about 30-40 hours of use, because the current has dropped off and the cathode is full of deposits.
I am looking at my Merck Index, It has basic characteristics of most common chemicals. It states: Copper very slowly attacked by cold Hcl or dilute sulfuric acid; readily by dilute nitric acid and by both hot concd H2SO4 and HBr.
Iron: Readily attacked by dilute mineral acids and attacked or dissolved, by organic acids; not appreciably attacked by cold concd H2SO4 or HNO3, but is attacked by the hot acids.
Nickel: Slowly attacked by dilute HCl or H2SO4; readily attacked by nitric acid (I found Nickel would not dissolve well in nitric unless I heated it).
(Dosn`t state what concd H2SO4 would do to nickel.)
I take it then that you had to keep your tank and solution from getting hot.
I have read electro stripping articles that describe the stripping action on gold plate or bullion. The gold never goes into solution in sulfuric. The underlying base metal is attacked through microscopic imperfections in the gold plate. These metals oxidize and go into solution. This loosens and breaks up the gold plate into fine bits. You can see the yellow glitter falling or floating. Some of its black. (thats why I like to use that Triton x-100 surfactant).
In the case where you have gold brazes or kt gold, the gold will be so fine that you see a black mud. And here the base metals have to go into solution or plate out; or if the solution is overloaded fall to the bottom with the gold .
That 10% water you mixed with the sulfuric acid provided a place where the base metals could go into solution. The metal sulfates are ionized here and this increases the current flow. I think concentrated sulfuric does not ionize as well as dilute sulfuric.
I think it all depends on what your anode is made of, which helps you decide how to run the cell. Temperature also figures.
It does take a lot of experience!
I`m going to try concentrated sulfuric in the cell with some CPU`s I have (10% water!). That was a great tip on the fact that CPU pins are electrically connected. I can hang them by one pin and zap em! The pins are magnetic and must be some flexible alloy of iron and cobalt. I had a previous tedious separation with ferric leach and a AR procedure with CPU`s. I had to get rid of a lot of ferric before I could precip the gold. This should be much easier.
Thanks to everybody for all your comments, much appreciated.
------- Aleagle2
Well-known member
Oh GSP, I wanted to add I will also use a mild steel cathode in the cell. Thank You. ---Al
eagle2
Well-known member
Hi Aflac; Yes, chilling should work well on cleaning out solutions. I used a carbon anode and a copper cathode. It works. The carbon does erode and black bits fall to the bottom, but none of it goes into solution. You can leave it in and remove it with the next gold cleanout. Or drain the tank and remove it from the bottom. but I would hesitate if using concd sulfuric. ---- Al
macfixer01
Well-known member
eagle2 said:Hi GSP; Thank You for all those tips. Well taken.
---Snipped!---
I`m going to try concentrated sulfuric in the cell with some CPU`s I have (10% water!). That was a great tip on the fact that CPU pins are electrically connected. I can hang them by one pin and zap em! The pins are magnetic and must be some flexible alloy of iron and cobalt. I had a previous tedious separation with ferric leach and a AR procedure with CPU`s. I had to get rid of a lot of ferric before I could precip the gold. This should be much easier.
Thanks to everybody for all your comments, much appreciated.
To Eagle2 (or anyone else who knows)... I was confused by your comment. What does the reference here to the CPU pins being electrically connected mean? Does this imply there is some high resistance connection perhaps between every pin on a CPU? I really don't think that's likely but I suppose it's possible? I can't say I've ever tested for that.
Thanks,
macfixer01
