# Silver recovery from coins



## Buzz (Oct 15, 2007)

Hi Folks,

I'm looking at 10Kg of old english silver coins.
They are all post 1920 up to 1947 therefore 50/50 with copper.

I was going to nuke them with Nitric and then recover the silver using the "old" method (salt, lye, dextrose).

Would i be ok using Nitric and the Copper cementation method as in steves video.
If so, what kind of purity would i likely to achieve?

Any pitfalls i need to be aware of?

I realise i'm asking a lot of questions lately, don't want to test your patience. I learn quick and hope to give something back in time.

Regards
Buzz


----------



## goldsilverpro (Oct 15, 2007)

Probably 99% pure at the most, depending on how much care you take.


----------



## aflacglobal (Oct 15, 2007)

I realise i'm asking a lot of questions lately, don't want to test your patience. I learn quick and hope to give something back in time. 

Ask all you want Buzz, That's what all this is for.

Are the coins not worth more now than the silver value would be ?


----------



## lazersteve (Oct 15, 2007)

Buzz,

Some of the 'pitfalls' of this method are:

 Use of old copper contaminated with other materials/chemicals.
 Lack of through washing to remove the blue copper nitrate from the cemented silver powder. Wash the silver powder 5-10 times with hot water, or until the rinse water is no longer turns blue when tested with NH4OH.
 Pieces of copper in the silver powder. Don't use wire or thin copper to cement.
 Incomplete cementation caused by using too little copper.
 Using excess Nitric Acid will consume more Copper and produce more fuming when the silver is cemented. Do your math before hand and start with a little less nitric than required. Work your way up to the calculated value if required to dissolve the coins. Use an equal volume of distilled water. The General Reaction list details how much nitric to use.

As Ralph said, be sure the coins are worth less than the value of the silver.

Steve


----------



## Harold_V (Oct 16, 2007)

goldsilverpro said:


> Probably 99% pure at the most, depending on how much care you take.



Yep-----what GSP said. 

It's generally considered proper procedure to electrolytically part the resulting silver for further purification. 

There's no way in hell I'd recover silver as a chloride unless it's absolutely necessary. You can do it with copper much faster and easier, with roughly the same results, and one tenth the headache. 

Harold


----------



## Buzz (Oct 16, 2007)

Thanks for the info guys, appreciate it.

The coins are worthless as far as collectors are concerned due to condition and they have no face value at all.

I was going to use copper piping as used by plumbers in households.
Would this be considered pure enough to use?

Thanks again

Buzz


----------



## Harold_V (Oct 16, 2007)

Copper pipe is very good--it's electrolytic pure copper. I would caution you to not use any solder joints. The copper pipe should be clean of any contaminants, which would report in your silver. Do not use any solder joints. 

The one thing to watch for is total dissolution of the copper. As pipe dissolves, it's no different from any other form. It gets thinner and thinner, then breaks up in small pieces, and eventually is gone. Any you leave behind will report in the silver, which lowers its quality. It is for that reason that the use copper wire be avoided. It borders on the impossible to remove the tiny fragments that are often left behind. Large pieces are very best, for they live a long time, and are easily removed from the silver after the fact. 

Parting the recovered silver in a silver cell will remove the copper, but you also limit the useful life of the electrolyte as copper is accumulated. That is the limiting factor in determining how long it works well. 

While it's commonly accepted practice to start parting silver with some copper in the electrolyte, I ran my cell for years, always beginning with pure silver. Copper accumulates fast enough, and the effect on the silver is very noticeable. At first, with pure electrolyte, the silver deposits in a fairly hard layer to the cell (mine was stainless), and then starts growing random crystals. They entire lot will often scrape off in a strip. Copper makes the crystals grow much softer, so they strip easily, and it also prevents the initial solid deposit. You'll have to weigh that information to determine if the limited amount of scraping you'll have to do is worth the time it takes to recycle your electrolyte more frequently. 

Problem is, when you start with copper, as you exceed a given level of copper concentration, you start co-depositing copper along with the silver. 

Once the point of co-deposition is reached, the deposit is very fine in nature, and soft. It wipes off the cell very easily. While you can't see the copper, when you dissolve crystals to make more electrolyte you'll see the slight discoloration, (not the green, caused by fumes from the nitric), but a light blue/green color. From this you can conclude that you have, for all practical purposes, defeated the purpose for running the parting cell. 

Unless you intend to finish the silver by parting, I see no good reason to process the coins. They would be far more valuable to you for inquarting, assuming you refine karat gold. 

I question your claim that the coins are 50/50 silver/copper. Most coinage is much higher. Canadian coins were 80% as I recall, and US silver coins are 90% silver. Are you sure yours are only 50%? I'd expect much higher. 

One more thing. 

Unless you're making electrolyte, you need not use distilled water. While it's true that you will precipitate minute traces of silver chloride using tap water, even tap water that is treated with chlorine (mine was), you can use it with very good results when digesting silver intended for recovery. The losses will equate to far less expense than the cost of distilled water, and it's far more convenient. The losses are often recovered when the slag that comes from melting the cement silver is further processed, so you don't really lose anything of mention. 

The use of distilled water is way over rated for refining-----although it does have a place. Making test solutions is one of them. Making electrolyte is another. The contaminants in water, in general, do not report in metals when they are melted. I turned out excellent quality gold using tap water, always. 

You might keep that in mind should you start processing. 

Harold


----------



## Buzz (Oct 16, 2007)

Thanks Harold,

As always, some great advice.

The British silver coins were sterling silver up to 1919 but during 1920, the content was reduced to 50%. Then, during 1947, the silver was left out altogether.

For anyone interested:
http://24carat.co.uk/silvercontentofcoinsframe.html

Kind Regards
Buzz


----------



## goldsilverpro (Oct 16, 2007)

I have used copper tubing quite a few times, but only when I couldn't find copper buss bar in a scrap metal yard. They will cost about the same. IMHO, buss bar is the very best. Silver will also cement on the inside of the tubing and it's a pain to get it out, especially if the tubing ends have flattened together when cutting it - use a tubing cutter. Buss bar is so thick (1/4") that there is hardly any chance of copper slivers falling off into the cemented silver. Just make sure there is no solder or silver or tin plating on it. You need bare clean copper.


----------



## Harold_V (Oct 16, 2007)

Buzz said:


> The British silver coins were sterling silver up to 1919 but during 1920, the content was reduced to 50%. Then, during 1947, the silver was left out altogether.



Interesting. Also, had I noticed your location, it may have made more sense. I wondered how you'd come by so many British coins!

We in the US followed a similar course, but at a much later date, as you may know. I can only assume that we were slow to learn.  

Thanks for the enlightenment. 

Harold


----------



## hungry (Nov 10, 2007)

Does anyone know the silver content of Australian coins? I have a few dated between 1947 and 1963.


----------



## Lou (Nov 10, 2007)

Just curious, but why not use zinc instead of copper to cement? It works very well, and excess zinc removed by dissolving away with hydrochloric acid.

Zinc is also cheaper than copper is, by about a third.


----------



## Buzz (Nov 10, 2007)

hungary,

The australian coins were 92.5% (Sterling) Silver up to 1945.

From 1946 to 1963, they are 50% Silver.

1964 onwards, no Silver.

Regards
Buzz


----------



## Harold_V (Nov 10, 2007)

Lou said:


> Just curious, but why not use zinc instead of copper to cement? It works very well, and excess zinc removed by dissolving away with hydrochloric acid.
> 
> Zinc is also cheaper than copper is, by about a third.



Zinc isn't selective, so you don't achieve your intended purpose. It precipitates copper along with the silver. The exception would be if one was capable of performing a perfect stoichiometric conversion, whereby the zinc precipitated the precise amount of copper required to precipitate all the silver in solution, and dissolving all traces of elemental copper in the process. I think that's beyond the ability of almost anyone working as a home refiner, although I could be wrong. 

Remember, the purpose here is to purify silver, not just recover it. If you intended to reuse the recovered metal for inquartation (not really a great idea unless one has no other metal source for inquartation), zinc would work adequately. Silver that is introduced to a silver cell should be of the highest possible quality to insure respectable life of the electrolyte. 

Harold


----------



## hungry (Nov 11, 2007)

Thank you for the information Buzz.

ED


----------



## Lou (Nov 11, 2007)

Oops, I don't think I wrote that properly. I meant once he had the silver chloride instead of using the old Karo syrup trick. Zinc, silver chloride, sulfuric acid works. Otherwise zinc is kind of useless, as it's far enough down the electromotive series that it'll drop a bunch of undesirables out.


----------



## Harold_V (Nov 11, 2007)

I thought your question was rather strange, coming from someone with a chemical background, and considerable understanding of the process in question. 

I always avoided creating any unnecessary silver chloride. It was much easier to recover silver from solution with copper, and I managed to keep a steady supply from processing heavy contacts for customers. The only real negative is that the recovered copper had no market, and was discarded at the land fill. Economically, that wasn't the best scenario, but the price of copper was low. Today, that's not the case, although there's still no market for the copper in sludge form.

My routine was to use aluminum scrap when I converted any chlorides, but, being a machinist, with access to identifiable material, I was able to avoid adding alloys that were troublesome. 6061 aluminum contains almost nothing that will contaminate silver, and was the most commonly used alloy I had at my disposal. Zinc might have been a good choice, too, but I didn't have it in quantity the way I did aluminum. My choice was a matter of convenience. 

Harold


----------



## knightee (Jan 4, 2008)

how did this turn out i have 2kg of 50/50 coins ?????????


----------



## Harold_V (Jan 5, 2008)

knightee said:


> how did this turn out i have 2kg of 50/50 coins ?????????



Not sure I understand your question, but if I had the coins and wanted to extract the silver, I'd simply dissolve them in nitric acid and water, then recover the silver on scrap copper. You can expect about 99% purity by that method. The cement silver can then be melted, cast in an anode, and electrically parted for further purification.

Harold


----------



## knightee (Jan 5, 2008)

The coins are 50% silver , what percentage of silver could i achieve by using the cathode method after i make the powder from nitric acid. Can the cathode elocrolysis (sp :? ) be recreated at home on the cheap


----------



## Harold_V (Jan 5, 2008)

Depending on your work habits and handling after the silver is parted, you could expect a purity as high as 9999. 

I ran my silver cell without the addition of copper in the electrolyte. What I learned from doing that is that the silver plates out very firmly and well attached at first, then as the level of copper (in the electrolyte) increases, a product of the refining process, the deposit becomes softer, and less firmly attached to the cathode. 

As the process continues, the deposit further changes in nature, eventually growing long, stringy and spongy threads, which start to include traces of copper. From this, you can clearly conclude that if you keep the copper level quite low by frequently changing the electrolyte, you can produce a high level of purity. 

The anode must be contained in a bag (or filter, assuming the anode isn't suspended vertically) that captures particles that are regularly shed as it is consumed by the process. These particles would be traces of other values (gold, platinum, palladium, etc.) along with a large amount of silver particles. Copper, as already stated, goes into solution. 

This can be accomplished at home, but it would not be a good idea for a single batch. A cell is required, along with a power supply. You could easily spend far more than the value of the silver, which would not make sense. 

If, on the other hand, you want to learn to refine silver, then you're on the right track. 

Harold


----------



## goldsilverpro (Jan 5, 2008)

This "knightee" coin part of the thread sort of continues here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=1428

And, here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=1422


----------



## depperl001 (Aug 14, 2010)

Buzz said:


> hungary,
> 
> The australian coins were 92.5% (Sterling) Silver up to 1945.
> 
> ...



Hi,
The Australian 1966 50c coin was/is 80% Ag + 20% Cu

Regards,

Josef Vavryn


----------

