# Recovery of silver solder with 34% silver content



## Etfonedhome (Jul 12, 2017)

:mrgreen: Hello all. 

My name is Emmett, and I have several pounds of 34% silver solder scrap. The rods also contain tin, and copper. 

My employer has authorised me to collect it, as they did not recycle or reuse it. they have been throwing it in the trash. The rule is any scrap must be below 2 inches In length.

I have access to a 5 gallon bucket full, but would like to run a small known quantity test batch, to determine if there is a viable return on investment. 

The biggest hurdle is, my knowledge of chemistry is limited to: don't drink the chemicals, don't get them in your skin or eyes, and don't breathe the fumes..... (im under estimating my ability only slightly, for saftey's sake)

I Have access to the msds for exact chemical content.

Is anyone here willing to help a dummy learn? If so, what would we call a smart first step?

Thanks for your time


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## nickvc (Jul 12, 2017)

Welcome to the forum.
Your biggest problem may well be access to nitric acid which will be needed to recover the silver from the solder, price can also be very high for small quantities.
The value of the silver you presently have is around $155 which is about 10 ozs of silver so the first thing to work out is how much the nitric acid will cost against the value of the silver. The process to recover the silver is very simple simply dissolve all the metal and then cement the silver out using copper, cementation using copper will only remove less reactive metals such as silver gold and platinum group metals. There are hazards as the fumes produced are highly toxic so use of a fume hood is advisable or work with a fan behind you if you have no near neighbors.
You may well find collecting a larger quantity and offering it for either toll refining or for sale on here may be a safer, easier and less expensive route but perhaps less fun and less rewarding for not having achieved the end result with your own hands and gained knowledge.
What ever you decide I wish you luck.


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## rickbb (Jul 12, 2017)

First step is to get your hands on those MSDS sheets. Find out exactly what else is in the soldering rods before you stick them in anything.

You may have a simple recovery method, or a complex one if there is something nasty in there besides the silver.


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## goldsilverpro (Jul 12, 2017)

How much copper and tin? What about zinc? How do you know it's 34% silver? Does it say 34% Ag or does it say bAg-34?

There is a bAg-34 solder listed in many places on the internet, but it actually contains 38% Ag plus 32% Cu, 28% Zn, and 2% tin. If that's what it is, you could use 50/50 nitric to dissolve the alloy without too much interference with the metastannic acid produced by the action of the nitric on tin. If the tin is much higher than 2%, the complications will increase. 

At worst case, it would take about 1.5 liters of 67%-70% nitric plus 1.5 liters of distilled water to dissolve one pound of that alloy. A pound of 38% silver contains about $88 worth at today's silver spot of $15.91/troy oz. That's the intrinsic value. In reality, you would never get quite that much for it.


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## Etfonedhome (Jul 12, 2017)

The box says "34% silver content, with added tin for better solder flow, cadmium free" in that exact phrasing.

I will get the msds tomorrow. 

I also learned a fellow employee has a 5 gallon bucket nearly full, and he will give it to me, because the local recycler he found wouldn't buy it, (it was an auto salvage yard type of business) they said the cost of the reclamation process makes it not profitable for them. He only tried one place then gave up.

Im not looking to get rich, obviously, but more interested in the accomplishment of DIY, and learning something new, even if it's a break even scenario, I'll do it.


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## goldsilverpro (Jul 12, 2017)

It would be very helpful if you knew the copper and tin contents. What is the brand and ID number of this solder?


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## Etfonedhome (Jul 13, 2017)

Ok, the content is 33% Ag, 36%Cu, 29%Zn, 2%Sn, and 0.1%Si


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## Topher_osAUrus (Jul 13, 2017)

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=43&t=25315&p=268446&hilit=Wick+filter#p268446

Someone who was in your shoes, with a higher Ag content than yours


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## Etfonedhome (Jul 13, 2017)

Ok, so I'm slowly learning more and more about this process, and i guess my next question is, what about the copper and zinc? Is it recoverable/ worthwhile to do so? 

Primarily I'm thinking the general consensus seems to be the simplest method is dissolving in 70% nitric acid, then cementing out the silver with copper. 

Can the copper in the rods be reclaimed or used in some way for this process?


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## goldsilverpro (Jul 14, 2017)

Although I believe that dissolving in 50/50, nitric acid/distilled water is the only good way to pursue this, you should be aware of the disadvantages of this process.

*(1)* During dissolving, you will create a lot of corrosive, toxic, very visible, red-brown fumes that must be exhausted away from you and the workplace. This can't be done with close neighbors and it can't be done inside without a fume hood. If you do it outside you must stay upwind. There is no respirator available that will remove the nitric fumes. The dissolving will produce a lot of heat and can get quite violent and boil over. You can tame it down quite a bit by covering the material with the full amount of distilled water needed for the batch, then adding the 67-70% nitric in increments, and waiting for each nitric addition to quit reacting before adding more - stop adding when an addition produces no reaction. 

According to your figures, it will take about 1,440 ml of ~70% nitric and an equal amount of distilled water to dissolve 1 pound of your material, assuming it was done in an open top container. I would treat no more than 2-3 pound batches (per bucket) in 5 gallon plastic buckets.

*(2)* The solid, fluffy metastannic acid produced from the tin must be totally filtered out and rinsed before cementation - a slow process. With only 2% tin, this should work OK. Before cementation, the solution should be perfectly clear. 

It is best if the copper used for cementation is pure. The best copper to use is clean, non-tin plated, scrap buss bar with no solder on it, cut into lengths long enough to stick up out of the bucket and make it easy to remove them. Copper wire is a poor choice because copper slivers will fall into the cemented silver and contaminate it. Copper tubing can do the same thing. For each 3.4 pounds of silver cemented, 1 pound of copper will dissolve. This assumes that there is no extra free nitric aacid in the solution.

*(3)* The copper cementation will only produce a silver purity of about 99.0%. You might get better purity by dropping the silver as silver chloride and then reducing it to silver metal, although that process is trickier than cementation. To further purify this, you would need a silver cell and a melting furnace.

*(4)* You will end up with a lot of very colorful waste solution that is considered hazardous waste by the EPA. You can't dump it. You must treat it.


I have only outlined the basics. Needed details are found by searching the forum and asking questions. To get the hang of this, I would do several tests on about 25 grams at a time in a beaker before tackling larger amounts.


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## upcyclist (Jul 14, 2017)

Etfonedhome said:


> Ok, so I'm slowly learning more and more about this process, and i guess my next question is, what about the copper and zinc? Is it recoverable/ worthwhile to do so?


Looks like GSP touched on the rest of your question, so I'll just give a quick answer to this one: Yes, you can recover the copper in your waste process--definitely read Dealing with Waste if you haven't done so already. The zinc not so much--well, you can, but it'll be mixed in with the other metals you drop at the end.

Essentially, everything in your waste stream located below iron through copper on the reactivity table of metals will show up in your first waste cementation bucket. It'll mostly be copper, because we use it so much for cementing PMs onto (and other reasons), but there will also be tin and lead. Some folks have taken those solids and have managed to sell them as red brass. Others could melt it into ingots and purify them with a copper cell. 

But compared to the value of the precious metals we're refining, the non-precious metals are more of a happy byproduct if you can easily sell them and/or prepare them for sale. At a hobbyist or small refiner scale, it's hard to justify much in the way of expense or time to recover them.
_
Edit: In case it's not clear, the judgement call on what's 'worth it' is my opinion. Others will have different views._


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