# silver contacts from the relays



## teclu (Aug 13, 2009)

Hello everybody,


I have these contacts type from the relays(Ag 75%, Ni 25% ), riveted on the copper.
http://i31.tinypic.com/5fdfs8.jpg 
After nitric digestion(50/50), which is the ratio of NaCl (optimal), and after NaCl, for the silver chloride, which would the better way to convert it?

Many thanks!

teclu


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## Platdigger (Aug 13, 2009)

Don't make the chloride Teclu, just cement to copper.


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## teclu (Aug 13, 2009)

Platdigger said:


> Don't make the chloride Teclu, just cement to copper.




Ok, but how?


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## Oz (Aug 14, 2009)

Put a copper bar in your nitric solution and you will see elemental silver grow on it.


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## goldsilverpro (Aug 14, 2009)

teclu,

Since there is a lot of copper already dissolved in the 50/50 nitric solution, I would dilute it with about half of its volume using distilled water and stir. This will prevent any possible crystallization down the line.

Put a piece or two or three of copper in the solution. The more copper surface, the faster the silver cements out. The best is clean Buss bar from a scrap yard, with no solder on it. It is flat and thick and makes the silver easier to separate. Make the bars long enough so they stick out of the solution 3 to 5 inches - this makes them easy to get out. Copper wire is bad because the silver gets trapped among the wire and is hard to separate. Thin copper sheet is not very good because, when it eats through, thin slivers can fall off and blend with the cemented silver.

If there is excess nitric in the solution, it will first dissolve copper. When all the excess nitric has been consumed, spongy gray silver will start cementing on the copper and then falling off to the bottom. For each ounce of cemented silver, 3.4 oz of copper will dissolve.

After a day, more or less (depending on the surface area of copper bar you used), all the silver will be out of the solution. Stir (I usually slowly move one of the bars in the solution, back and forth, to stir), let it settle until clear on top, and test the solution by adding 1 drop of muriatic acid or salt water solution. If a white cloud appears (silver chloride), it is not finished - let it work awhile longer. If the copper bar gets well coated with silver (most falls to the bottom), the reaction will slow down. It helps, sometimes, to scrape the loosely adherent silver off of the bars with a plastic scraper or rod.

When finished, hold the bars over the solution, scrape them, rinse them down into the solution with a squirt bottle, and remove the bars. Allow to settle well and decant or siphon the solution off of the silver. Filter the silver sludge and rinse until the rinse water coming through the filter is not blue. The blue can be seen better by collecting a little of the filtered rinse water and adding a little ammonia to it.

At this point, the silver should be about 99% pure, or a little better.


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## teclu (Aug 14, 2009)

goldsilverpro said:


> teclu,
> 
> Since there is a lot of copper already dissolved in the 50/50 nitric solution, I would dilute it with about half of its volume using distilled water and stir. This will prevent any possible crystallization down the line.
> 
> ...





Platdigger, Oz thanks a lot for your advices!


GSP,
Sir many thanks!

You are a very good teacher, for me certainly.

Now I have few questions, the first: is bad if I use tap water to dilute?...
If the silver contacts are riveted on copper alloys(CuZn or CuNiZn), this change something the cementation process? 

Below are pictures of the silver contacts Ag85Cd15 not riveted(soldering).Soldering alloy and Cd can be a problem?

http://i31.tinypic.com/21g9ci9.jpg
http://i27.tinypic.com/adp7hq.jpg

teclu


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## goldsilverpro (Aug 14, 2009)

teclu said:


> is bad if I use tap water to dilute?...


If there is no sediment in the water, the chlorine added to tap water is about the only problem. It precipitates silver chloride which co-mingles with the silver. This silver chloride makes it hard to see what's happening and it will generally be lost during the standard process. It also makes the melting of the silver a little more difficult. You can boil the water for a few minutes to get rid of the chlorine or, let it sit in an open bucket for a day, or more. Stir it every so often.



> If the silver contacts are riveted on copper alloys(CuZn or CuNiZn), this change something the cementation process?
> 
> Below are pictures of the silver contacts Ag85Cd15 not riveted(soldering).Soldering alloy and Cd can be a problem?



Cd, Ni, zinc, and silver solder won't cause a problem. They all dissolve and the only things the copper will cement are the precious metals. That's the beauty of it.

In the second photo, I see some large points that appear to be silver soldered to heavy copper bussing. It is wasteful, in copper, chemicals, and waste generation, to dissolve all that copper. You can remove the points as follows. Don't worry about the silver plating on the copper - it's very thin. The large points, once removed, are dissolved in nitric, as usual. They will average about 81% silver. The points are 90%, but this is lowered by the solder and the copper that is picked up. Some large points are tungsten/silver (I don't see any), which are processed differently. They are thin, dark, heavy, and generally have a line or cross-hatch pattern on them.

1) Do this outside - upwind. Cadmium is usually present in the point and/or the solder - the smoke can very well be poisonous. 

2) Grab the part with pliers.

3) Heat the back, behind the point, with a torch. This will melt the solder. For safety's sake, try not to overheat. Don't melt the copper or the point.

4) Slide off the point on the edge of a coffee can.


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## lazersteve (Aug 14, 2009)

GSP,

Excellent post on the recovery of silver from nitrate solutions.

I noticed you stated that 1 ounce of silver requires 3.4 ounces of copper. This seems backwards to me as one mole of copper will hold two moles of nitrate and silver only holds one, from this I would think it would require less than an ounce of copper to recover an ounce of silver. 

I'm just trying to get the numbers straight in my mind and it seems backwards the way you wrote it.

Here's the balanced equation and my math:

Cu + 2AgNO3 = 2Ag + Cu(NO3)2

Meaning 63.5g of solid copper dissolves and 215.8g or solid silver is recovered.

The ratio of silver produced to copper dissolved is:

215.8 / 63.5 = 3.4

So 1 ounce of dissolved copper produces 3.4 ounces of recovered metallic silver.

Steve


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## metatp (Aug 14, 2009)

goldsilverpro said:


> Since there is a lot of copper already dissolved in the 50/50 nitric solution, I would dilute it with about half of its volume using distilled water and stir. This will prevent any possible crystallization down the line.
> 
> Put a piece or two or three of copper in the solution. The more copper surface, the faster the silver cements out. The best is clean Buss bar from a scrap yard, with no solder on it. It is flat and thick and makes the silver easier to separate. Make the bars long enough so they stick out of the solution 3 to 5 inches - this makes them easy to get out. Copper wire is bad because the silver gets trapped among the wire and is hard to separate. Thin copper sheet is not very good because, when it eats through, thin slivers can fall off and blend with the cemented silver.


GSP,
Thanks from me also. I have one question. I have been using copper piping since I already have some. I noticed the same thing you mention with copper sheet when I have excess nitric. I avoided most of the issue when I used up th nitric by adding more silver, but leaving it over night was sometimes an issue of very small sliver falling off. What I do to keep the purity high is routine stilling and removing the copper piping every once in a while. Unless I am adding a new fresh piece of copper toward the end, I don't leave it in overnight. Will the Buss bar would help me avoid this extra steps? I am not in a rush, but it would still be nice to let it sit overnight with no worries.




goldsilverpro said:


> The blue can be seen better by collecting a little of the filtered rinse water and adding a little ammonia to it.


Never thought of using ammonia. I usually have to get my wife's opinion of when it is clear. And even after that, I rinse it a couple more times.

Tom


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## goldsilverpro (Aug 14, 2009)

Tom said:


> Never thought of using ammonia. I usually have to get my wife's opinion of when it is clear. And even after that, I rinse it a couple more times.


Use a small beaker or clear jar (I like a test tube) for the rinse sample. Add enough ammonia to make it alkaline - just guess - it only takes a few drops for 10-20 ml of rinse water. The ammonia forms a very visible blue complex with the copper. Try it with a couple of drops of copper solution diluted to 10 ml with water. It helps to see it if you put a white piece of paper behind the beaker. This also works great when rinsing crystal from a silver cell.



> Thanks from me also. I have one question. I have been using copper piping since I already have some. I noticed the same thing you mention with copper sheet when I have excess nitric. I avoided most of the issue when I used up th nitric by adding more silver, but leaving it over night was sometimes an issue of very small sliver falling off. What I do to keep the purity high is routine stilling and removing the copper piping every once in a while. Unless I am adding a new fresh piece of copper toward the end, I don't leave it in overnight. Will the Buss bar would help me avoid this extra steps? I am not in a rush, but it would still be nice to let it sit overnight with no worries.



With the Buss bar, you can leave it overnight, or longer, with no problems. Ask the scrap metal dealer if he has Buss bar scrap. They often keep the heavy valuable stuff out of sight. Get the copper colored bar with no tin or silver coating or solder on it. It is usually found 1/4" thick in various widths - usually 2" through 6". I usually try to find the 2".


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## goldsilverpro (Aug 14, 2009)

Steve said:


> I noticed you stated that 1 ounce of silver requires 3.4 ounces of copper. This seems backwards to me as one mole of copper will hold two moles of nitrate and silver only holds one, from this I would think it would require less than an ounce of copper to recover an ounce of silver.
> 
> I'm just trying to get the numbers straight in my mind and it seems backwards the way you wrote it.



You're right, of course. I've made that same error before. Got to watch myself. Also, in the silver cell, one ounce of copper entering the solution will reduce the silver in solution by 3.4 oz. Same deal. There's only so much NO3- to go around.


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## teclu (Aug 14, 2009)

goldsilverpro said:


> teclu said:
> 
> 
> > is bad if I use tap water to dilute?...
> ...





Sir,

Thanks again!

teclu


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