Dissolve silver

[borostmcbarna]

Hi.
I am actualy looking for some information for dissolving silver.I am wondering what chemicals are disolving silver and how fast,..except nitric acid of course that we all nkow it does.
I am working on some very cool stuff,and i just need a little help for the dissolving chemicals and will post my experiment results and detailles a little bit later on.
Thanks.

 

[nickvc]

Nitric is usually the acid of choice to dissolve silver as it's easy to recover, the only other acid that leaps to mind is sulphuric but that's not so easy to deal with. We need more details of what your working with to have some idea as to what to suggest to avoid any problems.
Is it plated, what other metals are involved, are there any other values, are there plastics, they all make a difference.

 

[borostmcbarna]

actualy i am trying to deplate silver plated flatvare,with a custom made cool machinery i am working on a prototype right now and i am looking for the best and fastest way to deplate actualy to disolve the silver or the base metal with recovering the silver at the end of the line.There are no plastics involved just silver plated flatvare,chemichals and electricity and mechanichal movements with moving the flatware pieces rubbing them inside the machine.And of course avoiding work with nitric acid if it is possible because of the hazzards.
Thank you

 

[goldsilverpro]

Everybody wants to strip silver. Silver plated scrap is everywhere and is cheap. Have you ever wondered why? No one wants it because no one has ever figured out a profitable way to process it. Silver is usually plated on copper and many of the possible strippers want to attack the copper as fast or faster than the silver (examples: nitric or cyanide). The things that will only attack the silver are dangerous or troublesome or both (examples: 95/5, sulfuric/nitric, at 190F, or the sulfuric cell).

 

[borostmcbarna]

I think there are some fellows out there there figured it out,it is not that there are manny possibilityes to do it.Just a moment please,is the sulfuric cell what you mentioned the sulfuric acid used as electrolityc cell ?Thanks

 

[nickvc]

There are a few details on the forum on how to strip silver plate but as GSP pointed out most are too time consuming, costly or hazardous, it can be done but you can't make money doing it as far as I have managed to determine.

 

[goldsilverpro]

I think there are some fellows out there there figured it out,it is not that there are manny possibilityes to do it.Just a moment please,is the sulfuric cell what you mentioned the sulfuric acid used as electrolityc cell ?Thanks

I don't think anyone has really, really figured it out. Recently, someone on the forum experimented using the electrolytic concentrated sulfuric cell (the same cell commonly used to strip gold on the forum) and seemed to have some luck, although I don't remember the details. The sulfuric cell will strip the silver readily and not attack the copper. The problem is in recovering the silver after stripping. I thinks that's what the thread focused on. Maybe someone can give a link for that thread.

I've probably played around with this as much as anyone and have tried about everything, except I never tried the sulfuric cell. The best luck I've had was in electrolytic highly alkaline cyanide - about 30-45 g/l sodium cyanide (NaCN) and 120-150 g/l sodium hydroxide (NaOH), at about 4-6 volts. The large amount of NaOH seems to prevent the copper from dissolving and the silver dissolves and plates out on a SS sheet cathode.

 

[Harold_V]

Chris,
You likely recall that I never operated the sulfuric cell that I built so long ago. As a result, I can't contribute anything from experience based knowledge, but, if memory serves, sulfuric acid won't hold in solution much silver, and then, only when quite hot. Boiling sulfuric used to be used in cast iron kettles to remove silver from slimes, for example. I do stand to be corrected if I'm wrong.

I'm of the opinion that if the sulfuric cell is used to strip silver (seems to me the patent suggests it works), once it reaches the point of saturation, it should self precipitate, much like gold does as it migrates away from the anode. That which does not self precipitate could be recovered on copper, as it would be from a nitrate solution.

Comments?

One of you guys should take the initiative to experiment with a small cell, stripping a few pieces of flatware, to see how it behaves. I'm having more than a little trouble with the idea that silver can't be recovered economically by that method.

Harold

 

[Geo]

one method discussed was with the use of persulfuric acid or Peroxymonosulfuric acid H2SO5 solution saturated with copper as an electrolyte. the silver plate would go into solution and be cemented out on to a piece of copper in a corner of the cell away from the anode and cathode. cemented silver was collected in a glass container sitting in the bottom of the cell.all this was done in one operation. the pictures in the post was very informative. i'll try to find the thread.

 

[Harold_V]

one method discussed was with the use of persulfuric acid or Peroxymonosulfuric acid H2SO5 solution saturated with copper as an electrolyte. the silver plate would go into solution and be cemented out on to a piece of copper in a corner of the cell away from the anode and cathode. cemented silver was collected in a glass container sitting in the bottom of the cell.all this was done in one operation. the pictures in the post was very informative. i'll try to find the thread.

The interesting point here is that persulfuric acid is the product of a sulfuric stripping cell. It is created by high amperage, near the anode, but reverts back to sulfuric after migrating away from the anode. Armed with the knowledge that sulfuric will hold some silver in solution, and that there's a piece of copper in the cell, out of the electrical path, tends to support what I'm thinking---that a sulfuric cell can, indeed, be used successfully for stripping silver plated items. The copper suspended in the cell would be successful in keeping the content low enough to prevent self precipitation, but even if that was to occur, I expect it wouldn't be an issue.

Thanks, Geo.

Harold

 

[Geo]

heres the thread i was referring to.http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=12530

it seems to be pretty straight forward and a picture is worth a thousand words.when he started the thread, he listed sodium sulfate saturated with copper but i later ask him if it could be substituted sulfuric acid. we had a couple of conversations through PM as he was going to help me set up a cell and i ask if i could just use the stuff sold to clean pools with,persulfuric acid, and he said it would work as well.

 

[Geo]

by the way, for anyone wanting to try and make your own persulfuric acid, this is a very unstable compound in its pure form.it is a very strong oxidizer and can react to organics on contact.if you want to try this, use either the persulfate listed in the thread or one of the stable forms sold by pool supply companies.

 

[chemguy]

here is the thread GSP was referring to
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=50&t=13704&p=164057#p164057
post by mojeho describes the complete process.

 

[tek4g63]

Silver will dissolve in hydrochloric acid, or HCl, to form silver chloride, or AgCl. Silver chloride, however, is insoluble in water, which means a white solid of AgCl crystals will form in the resulting solution.

I do not believe that silver will dissolve in HCL without the aid of an oxidizer. Even then the proportion of how much silver does go into solution is directly related to the amount and type of oxidizer. At least that's how I understand it. I also believe the solution has to be hot. Once the oxidizer is consumed if the solution cools the silver will drop back out as silver chloride. But to my knowledge HCL alone won't really dissolve silver.

I fairly new at this, so I could be wrong.

 

[g_axelsson]

Don't take that too serious, goldonline is just spamming the forum to get their link in a number of places. :evil:

Göran

edit : Feel free to remove this post now when the spammer is gone.

 

[tek4g63]

Yeah I thought that was the case. But it burns me up when they do it with incomplete or incorrect information.

 

[jimdoc]

Goldonline has been warned already;
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&p=163085#p163085

All of his posts need to disappear, as his only intentions are very clear.

Jim

 

[canedane]

Im a absolut newbee here ,scrap metal is my normal buisnes,but i dare to come up with an idea.
The silver can be removed with quartz sandblasting sand in a concrete blender with a rubber drum instead the normal steel drum, and only a little of the cobber/brass wil be removed.
I guess i will be cheap to do the rest of the proces with nitric.
I have a stonepolish drum, and i will try to do the experiment i a small scale if my idea isent to far out.
Henrik

 

[nickvc]

Henrik welcome to the forum.
I think if I remember correctly someone was doing this or something similar some years ago, the problem is its slow and due to the shape of much plated silverware it won't strip or abrade off at the same extent over the whole piece meaning large amounts of base metals and so the cost of recovering the silver with nitric starts to rise rapidly.
The only way I can see to get a decent return from this material is to melt and assay it and send it to a large copper refinery which can slowly add it to its anodes and then recover and refine it from the slimes. The problems with this is the need for very large bars to make it viable, slow returns and the fact that the base metals forming the body of the flatware can be all sorts of metals some of which can carry penalties from the copper refinery.
Until silver reaches a more realistic value compared to gold much silver plated scrap will be just dumped as the cost of recovery is just to high to justify the work and costs.