Refining silver from scrap

I can direct you in proper procedures, but before you decide to proceed, know that you must have the ability to purchase nitric acid, and be able to handle it safely. A fume hood will be required, and a method of disposing of solutions contaminated with spent acid solutions bearing iron and other metals can't be avoided. . Copper is easily removed, so that's not an issue.
Silver purchased in Mexico always runs the risk of not being silver at all----and it often is not. A nickel alloy, commonly known as German Silver is used, and may not be readily recognized by the novice. There is a testing solution made from nitric acid and potassium dichromate that tests for silver---and is full-proof. It should be used on all pieces, regardless of markings, to ascertain that they are, indeed, silver. It also is wise to use a magnet. It's not uncommon for items such as chains to be made of steel, and rhodium plated. You will likely come to understand that a lot of things you think are silver are not.
Silver, in order to be pure, must go through a minimum of two processes. The first one is the dissolution of the silver, then the recovery from solution. The second one is the electrolytic parting of the silver to remove traces of contamination. The ability to melt silver and cast anodes is a requirement----although silver can be processed through the first operation without being melted. You would need a low voltage DC power supply, and a stainless container to function as a parting cell.
Give some of these things some consideration before you ask me to dedicate time----it's not something I can do in minutes, and I have a full schedule.
Harold

snip------- Sigh!
Just a correction to the first post, posted in haste. My comment should read
and is *fool*-proof.
Harold

Thank you very much!

Hit send instead of save on previous.
I have found a few sites that describe at a high level what you state below. But I'm looking for specifics.
For example:
Where would one purchase Nitric Acid? Is a license required?
Safety and environment are important so how do you handle for storage, disposal and use.
You mention a hood which raises another question, what equipment is needed and can some/all of it be made from items I can get at the hardware store and still be safe?
The process itself has been described as two parts, dissolve/suspend the silver and then separate it. You allude to this process not being complete without a third part, melting to further refine. I would guess that requires a furnace and melting to purify and then disposing of the excess, "slag" right?
I have seen some sites that give instructions for building a furnace from common materials (ex: 50 gal drum lined with refractive cement). Do you agree with this?
There's a lot to this I know and if you are too busy I'll keep on searching. If you have time to enlighten me on any of the basics I would appreciate it,
- ben

Hit send instead of save on previous.
I have found a few sites that describe at a high level what you state below. But I'm looking for specifics.
For example:
Where would one purchase Nitric Acid? Is a license required?
Safety and environment are important so how do you handle for storage, disposal and use.
You mention a hood which raises another question, what equipment is needed and can some/all of it be made from items I can get at the hardware store and still be safe?
The process itself has been described as two parts, dissolve/suspend the silver and then separate it. You allude to this process not being complete without a third part, melting to further refine. I would guess that requires a furnace and melting to purify and then disposing of the excess, "slag" right?
I have seen some sites that give instructions for building a furnace from common materials (ex: 50 gal drum lined with refractive cement). Do you agree with this?
There's a lot to this I know and if you are too busy I'll keep on searching. If you have time to enlighten me on any of the basics I would appreciate it,
- ben

Hello Ben:
The old "Amateur Telescope Making" books have procedures for recovering silver from mirror-silvering wastes. Some libraries will have the three volumes (editor was Albert Ingalls, I think). I don't recall which volume(s) had the silver recovery information.
If memory serves, one of the methods involved precipitating silver chloride, then mixing it with a flux and heating in a crucible to a high temperature. For silver scrap that would probably mean dissolving the silver in nitric acid first, then adding salt solution, then allowing the white matter to settle, decant the solution, wash the mass thoroughly with distilled water....
Silver isn't horribly expensive; unless there are some sentimental reasons for recycling your material, it might be cheaper and would certainly be less effort to trade the scrap to a reputable jeweler for silver ingot or wire or whatever.
Regards -- Terry

The way we did it back in college was this.
First sort out the dud material. steel, zinc, dental alloy etc.
Melt the silver and pout it slowly into a bucket of cold water. This produces shot with a large surface area to weight ratio.
Then we would pour nitric acid into an old crock pot, heat it up and gently add the silver shot and try not to breathe.
Add acid and water as needed until it was completely dissolved and the acid nearly spent
When cool, this solution was very carefully decanted off. Any brown fluffy stuff in the bottom could contain gold or platinum so filter and rinse it and put it somewhere safe.
The solution you decanted off contains mostly silver and copper nitrates. To separate these you add salt. The silver will precipitate out as silver chloride.
Decant off the excess solution and filter and wash the precipitate.
There is a method for separating the chlorine but I don't remember it. We would just put it in a crucible in the forge and burn it out, with a resulting plume of chlorine gas.
I wouldn't stamp it .9999 fine, but it worked ok for our mokume research.
This worked ok when silver was over $30 an oz and we could scrounge the nitric from the chemistry dept.
Nowadays you would probably go though 50 bucks worth of nitric to get 25 bucks worth of silver.
If you have enough, send it to a refiner and take the payout in fine silver shot.
Paul K. Dickman

Thanks Paul and Terry,
Appreciate the responses. The deal breaker is Nitric then. If it truly costs more in nitric (at retail) to separate the silver then the silver is worth then I'll bag it. I thought you could recover the nitric and re-use it another time or two. If that was the case then with silver now at $12.75 oz it'd be worth it, if not I'll likely do as you say and send it off.
Once again thanks,
- Ben

That doesn't work. When you use nitric acid, the thing that does the work is the hydrogen, which is displaced by silver. The solution you end up with is silver nitrate, and the hydrogen is released to the atmosphere. Assuming you have used a proper amount of nitric, or less, there ceases to be nitric acid present, so there is nothing to recover. You can safely look at acids much the same way you do fuel in the tank of your automobile. It does work, and when it is finished, you no longer have the fuel, although, in the case of acids, you still have the solution in which it was dissolved.
A gallon of nitric acid will dissolve a lot more silver than it's worth------a lot more! 30 troy ounces of fine silver can be fully dissolved with 1 liter of nitric acid. You would expect a reduced yield from silver alloys, because copper requires considerably more acid, pound for pound, as compared to silver. To get maximum yield, you have to let the acid do its work through gentle heating, allowing time----and not use excessive amounts, which yield problems in successive operations. Water, too, adds to the efficiency, forming the hydronium ion. Pure nitric acid dissolves silver at a reduced rate and efficiency as compared to water/nitric mix.
While the methods proposed by others work, they are not well accepted. Working with silver chloride is less than a pleasure, plus the volumes you start with are huge compared to the elemental silver that is converted from the chloride. Furnace reduction of several ounces of silver would require a large crucible to accommodate the chloride, and the reducing agents recommended cause serious dissolution of the crucible, so it becomes a matter of economics.
It is common practice to recover silver from solution with copper, which yields a fairly high grade of silver. While nearly pure, it's still in need of final parting, or electrolytic refining. That step should not be ignored, particularly if working with precious metals in general, for the silver becomes the carrier of many of them, the platinum group in particular. Traces of precious metals are recovered in the electrolytic cell, and can be difficult to recover otherwise, especially the platinum group. Separating gold from silver is dead easy.
Tap water is not acceptable when dissolving silver. The chlorides contained within will precipitate some of the silver. While it's not lost to you, if your objective is to make electrolyte, it is contaminated by the precipitate. A small home still will provide ample distilled water, which I highly recommend, depending on the nature of the recovery intended. De-ionized water works equally as well as distilled.
Silver chloride can be converted to elemental silver by aluminum or zinc, it need not be converted in the furnace. That was common practice for me, depending on the nature of the silver I'd recover. Silver was primarily recovered with copper, as above, but when working with dreadfully dirty solutions, precipitating as silver chloride with salt was the better choice, to aid in cleaning the recovered silver. Silver chloride can be acid (HCL) washed to eliminate contamination from metals that are dragged down with the chloride.
My last year of precious metal refining was back in '94. By then, it was difficult to buy nitric acid, even as a business. With the advent of 9/11, I expect it will be most difficult to obtain, with a serious amount of documentation included should you be successful. I was paying slightly over $4/gallon at the time, and owned my own stainless 55 gallon drum, which would be exchanged for a full one. Part of my reason for selling the refining business was the ever tightening noose of regulations. That prompted an early retirement. I think you'll find that you'll have great difficulty buying the things you need to refine successfully-----and if you intend to recover the real value of your metal(s), you can do that only by proper refining. If you don't produce and market metals that meet or exceed industry standards, and become recognized as a refiner, your options are to sell your recovered metals to a scrap dealer or other refiner, something you will quickly come to realize is akin to getting a serous screwing, so you're worse off than when you started.
Understand that there is no slick way to process precious metals without getting fairly involved. I refined for 22 years, starting out with the intentions of owning pure gold when it was illegal to do so. By the time I had acquired enough knowledge to refine and was well underway with my "hobby", changed legislation (January '75) had legalized the ownership of gold, so what was an illegal hobby became very legal, and slowly evolved into a business. It was never planned as such. Back then, you could buy acids easily, from most any chemical supply house. There were few, if any, regulations prohibiting the purchase or handling of acids. That changed drastically by the time I sold the business.
Don't be discouraged by those that say you can't refine economically. You certainly can----but you must get serious about doing it---and come to terms with the idea that it doesn't work well with slipshod methods.
If you intend to proceed, I can provide a lot more information------just let me know.
Harold
If that was the case then with silver now at $12.75

[reply to Harold Vordos]
Mr. Vordos, thank you so much. I was a little discouraged by the other posts warning of cost effectiveness and about ready to forget about this thread. If my original post is taken from a cost effective standpoint exclusively it probably wouldn't be worth refining my current small silver scrap. So in that sense they are correct and the advice is appreciated. I'll confess that the real drive behind this is fascination with the process of precious metal refinement as well as the potential for a few extra bucks on the side at some point in the future. As you say this will take some effort and I'm willing to put in the effort.
I want to focus exclusively on silver. My current "stockpile" of scrap is insignificant. But my idea is to (after some experience refining very small amounts) continue to acquire scrap via garage sales, flea markets, etc where with good negotiation skills, one could obtain samples for far less than current spot. Bring the items home and conduct whatever preliminary purity test is required (what about field tests?). If the sample passes the test toss it in the "brine bucket" until the liquid has become saturated and is ready for separation.
Looking at the financial side assuming 1 liter can dissolve 30 troy ounces. I found a site that lists Nitric Acid 70% Technical at $50 a liter plus a $25 haz-mat fee and it appears I could actually order it online no questions asked (not sure about that though). I'll assume this is on the high end price wise. So for my $75 I have enough solvent for 30 troy ounces which has a current value of $380. As you probably know the haz-mat fee is a single per shipment fee so one could obtain more per shipment and reduce the cost per liter. To error on the conservative side lets say because of impurities, my own ignorance or some other reason 1 liter ends up dissolving only 20 troy ounces. We're still talking about close to $250 worth of metal for $75 plus the cost of the scrap. If I can obtain the material that will yield those 20 ounces for $4 an ounce I'd have about $155 invested to this point. Not considering the cost of other materials needed to finish the job and end up with .9999, and not to mention time. On such a small scale this is definitely not a scheme to get rich but it should prove to be a slightly better than break-even proposition right?
Financials aside I would still want to know how to safely do this if for no other reason than to satisfy my own curiosity. Your post raises even more questions so I'll get to it. I see this process taking quite some time so hopefully you're a regular here!
- Would I be breaking any laws that you are aware of by refining a small amount of silver in my garage (and I realize you are not an attorney, just that you are aware of)?
- You mentioned the "serious amount of documentation" that will come with Nitric, I'm assuming that will address all safety concerns I have right? (ex: storage, what do in the case of a spill, safety equipment, disposal, etc.)
- Don't see just plopping anything with a silver appearance into the mix as being wise. I am told certain metals do not react well with Nitric, how can I test the scrap to have some assurance this will be avoided?
- You and another site I read mentioned heating the liquid. To what temperature and for how long? Is this required or simply to speed up the process?
- How about a materials list to get us to the point where I can begin adding materials to the brine bucket (lol I know that's not a proper term)? It appears I could start with 1 liter 70% Nitric plus some distilled water and a proper container. What are the proportions of water/nitric or does that depend on what the exact scrap content is? And is there really a way to know exactly what's in the scrap? You mentioned stainless steel for a container is that your recommendation?
I think this is enough for now. Once again thanks for your replies, very much appreciated.
- Ben

If you want to try to learn,than by all means try. We used an old crock pot with the brown glaze in good shape. You will also need filter paper, funnels crucibles and some method to melt metal.
A fume hood would be nice, but it could be done outdoors with a breeze if you stay upwind. I pukes out a lot of fumes at the start.
But if you are hoping for a money making venture, you must understand some things about precious scrap.
If you can buy silver for $4 an oz, you have already made nearly all the money you can.
Refining it will not add value and can possibly reduce it's value.
If you get enough (20 oz) One of the larger refiners (Hauser and Miller, Hoover and Strong) will pay you on the spot for clean, legitimately marked silver alloys. Depending on your total weight they will probably give you 90% -95% of the value of the metal contained.
For unmarked, contaminated or alloys of dubious origin. They will do an assay. Last time I sent off my sweeps (1999 or 2000) The assay charge was $90 and an extra $30 to get a platinum assay. Then they paid me out at 98% of the value of the metal contained. It takes a couple of months, but the reputable firms pay you based on the spot price the day they receive your shipment.
If you send them an unmarked bar of fine silver, they will insist on the assay anyway and all you will gain for your work is the savings on postage.
Because of economies of scale, the only way I can see to make money as a small refiner, is to do boutique refining for the thousands of goldsmiths who are convinced that the big refiners are ripping them off.
Having done refining, I can't imagine they could possibly steal enough.
Yes, you are probably breaking laws doing it at home, but if you neighbors are far enough away, you should be able get away with it.
You do not want to risk a visit from a hazmat team however, that could draw interest from you insurance company, your mortgage company and any future home buyers.
Virtually all of us here are doing something in their home that is probably illegal. If you're careful and don't annoy the neighbors you can usually fly under the radar.
Paul K. Dickman

It's time to take this thing off line. If you're interested in more information, please contact me on the side. My email address is correct.
Harold

Thanks for your reply Paul, this information will be very useful going forward.
Take care,
- Ben

Good luck
Pick Harold's brain fully. He knows more about this than anyone I know.
Ours was a seat of the pants operation. I only evolved because each time a billet of mokume didn't bond we were left with a 2 lb block of copper with a half oz of gold and silver in it.
Be very careful. The Nitric acid, it's fumes and the Chlorine fumes burned out of the precipitate are extremely hazardous.
We were in our twenties, and thought we would live forever.
Paul K. Dickman

That's a shame - I for one am very interested in others' practical experience of silver refining.

Just trying to avoid boring folks with what could be mundane details. I could certainly include you in the information I may provide-----but I hesitate to make everything public----if for no other reason, I'd not enjoy being responsible for some person following my instructions and then having problems. I'm not convinced I'm doing the right thing in helping someone accomplish a task that can be harmful to them. Refining presents many hazards.
What to do? :-)
Harold

On Fri, 19 Jan 2007 08:08:32 GMT in rec.crafts.metalworking, "Harold and Susan Vordos" wrote, Want to make sure us lurkers don't learn too much, eh?

Thanks Paul LOL....and I intend to pick his brain as much as his schedule...and patience allows for =)
Definitely understand and appreciate the caution. I won't bring anything on this property until I feel confident enough that I know how to handle it safely and (more importantly) know what to do in case of a mistake. Wife would not be happy with a haz-mat team showing up at the door, husband in cuffs...oh that would not be good.
Once again thanks to all, this group is awesome.
Take care,
- Ben

Chuckle!
Nah, it's nothing like that. Now that I no longer make my living refining, I'm more than happy to help others, but I'm sure you realize that things I say can put me in an awkward position when some moron comes close, but doesn't follow instructions properly.
Working with nitric acid can be deadly------there are many explosive compounds so created----some of them very unstable. Simply combining one of the common household liquids with silver nitrate can be very interesting.
If people are prone to experimenting, not following instructions, I'd rather not be implicated when they blow up their house, or kill themselves. Years ago, when I was refining, a guy in town blew out a wall while refining. This guy had a doctorate in chemistry and should have known better. Maybe I was lucky, but I never had any of those problems. I learned from a book on refining, and I followed instructions.
Harold.