# precipitating silver with copper



## GuyDeWhitney (Sep 15, 2013)

I found out the best way to use copper cementing to get the silver out of silver nitrate by doing it right at first by chance, then the wrong way when I started fiddling with the evolution; small rods instead of large bits of Cu or powdered copper.
The silver mostly falls away from the copper and the rod, usually hollow, vanishes from the bottom up, minimizing copper contamination as after the acid holds all the copper it can.
Large pieces of copper will get a coat of silver that will fall away but, with visible discoloring from peeling away a tiny layer of half dissolved copper. Powdered copper works fine except at the end when you are likely to end up with a last dose of copper powder undissolved in the silver powder.


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## Geo (Sep 15, 2013)

sounds like you are using copper tubing. use a hammer to flatten the tubing. another way to help reduce copper contamination is to dilute the silver nitrate with de-ionized water. the cementation is slower but the acid is less likely to chew the copper up into small bits. try to reduce the amount of free nitric by dissolving as much silver into the acid as it will hold. if you only add the amount of acid needed to dissolve the amount of metal, that will also help. try adding an extra amount of silver once the reaction is complete.


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## JHS (Sep 15, 2013)

you could avoid copper ,by using salt.lazor steve has a free vidio on his site that will teach you the basics.
i make no claims as to knowing gold,but i do know silver.
when i process silver in nitric,i do it pounds at a time.slowly and in small amounts add nitric as the process stops.
when it looks as though everything is desolved,i filter it.after filtering it,i borrow a page from Harold,i add 1 oz of 999
silver.i then walk away from it for a couple of days.if i had any nitric left, the bar uses it up.if the bar is completly gone,i repeat it with another bar.then my solution has no extea unwanted material.i then proceed to use the salt method and always get the desired results.the sectet is pacience.
john


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## g_axelsson (Sep 15, 2013)

JHS said:


> you could avoid copper ,by using salt.lazor steve has a free vidio on his site that will teach you the basics.
> i make no claims as to knowing gold,but i do know silver.
> when i process silver in nitric,i do it pounds at a time.slowly and in small amounts add nitric as the process stops.
> when it looks as though everything is desolved,i filter it.after filtering it,i borrow a page from Harold,i add 1 oz of 999
> ...


Hi John, what is the advantage of using up the nitric acid? As you are precipitating the silver with salt the extra acid shouldn't make any big difference, it will be washed away when the silver chloride is washed.
You don't get rid of dissolved copper either, so I don't see any advantage of adding silver.

Göran


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## goldsilverpro (Sep 15, 2013)

g_axelsson said:


> JHS said:
> 
> 
> > you could avoid copper ,by using salt.lazor steve has a free vidio on his site that will teach you the basics.
> ...



I agree with Goran. Why rework silver that is pure? Especially when the odds are that the purity of the silver from silver chloride won't be 999. It's a waste of time and effort eliminating all the nitric, unless you use impure silver such as sterling.


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## maynman1751 (Sep 16, 2013)

What I don't understand is why would you convert silver nitrate to chloride. Why mess with converting the silver chloride with NaOH and Karo. The silver cemented from the nitrate is already elemental. Just filter it, wash with boiling water and dry. Or use it in your silver cell. :?:
Am I wrong about this?


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## mitchd (Sep 16, 2013)

maynman1751 said:


> What I don't understand is why would you convert silver nitrate to chloride. Why mess with converting the silver chloride with NaOH and Karo. The silver cemented from the nitrate is already elemental. Just filter it, wash with boiling water and dry. Or use it in your silver cell. :?:
> Am I wrong about this?





I am no expert and most of the time I just want to dump out the silver and leave it in with the copper that I recover from electronic and gold fill items as it just does not seem worth it....UNTEL I do work with the silver and sell it and find out that all my chemicals have been paid for with silver and a bit of profit to boot.
Using copper to drop out the silver works nice but it takes some time and works best when hot try heating 60 gallons of spent nitric acid loaded with copper and silver just to drop out the silver using copper. Using copper seem to work well for a time then the silver starts to get eaten up again after a bit of time and then it takes even more copper, I ran out of copper tubing a long time ago and buying copper to drop out silver seems crazy, I have recoved copper but its not that pure and makes very dirty silver. For me the dropping of silver out with copper just does not work fast enough or cheep enough and just wont get the very last bit of silver out with out a lot of time. the salt is very fast and with in the next day I can drain off the liquid, start to recover the copper from the liquid using iron that same day and keep adding fresh water to the AgCL, draining the next day, untel the water is clear and then store it AgCl for a day of H2SO4 + iron convertion back to Ag. This seems to work best FOR ME.

There are time when salt may be best and there are times when copper will be the best way to go. it's all in what works best for you.

Mitch.


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## JHS (Sep 16, 2013)

[

Hi John, what is the advantage of using up the nitric acid? As you are precipitating the silver with salt the extra acid shouldn't make any big difference, it will be washed away when the silver chloride is washed.
You don't get rid of dissolved copper either, so I don't see any advantage of adding silver.

Göran[/quote]

Hi Goran,
when it comes time to process waste,you will find it makes life
a bit easier.as far as an oz of silver,well i am not loosing anything.i do get it back,weather it be a gram or an oz.
john
p.s. why would i waste pounds of copper in the waste when i can use my method?


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## Geo (Sep 16, 2013)

actually, if you follow the waste stream, the copper will be recovered before disposal. you may have to use very inexpensive steel to reclaim the copper but its really a small price to pay. cemented silver can be 99.5% if you are really diligent about your work habits (from other members observations). each person develops their own way of dealing with certain problems. many, like me, find it easier to just reduce the silver to elemental silver straight from solution. there are other members that use copper to cement their gold and swear by it. i wouldn't do it unless i had no other choice. they seem to have built their process around cementation rather than precipitation and it works for them. if your objective is to reclaim your metal as pure as you can and cementation works for you, who can say its wrong?


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## butcher (Sep 17, 2013)

Any time I can, my choice is to cement the silver from the silver nitrate solution with copper metal.

In Ideal conditions I prefer a thick solid piece of copper electrical buss bar, I also like the ones which are silver plated, so I can also recover that tiny bit of silver.

There are times where I may use other copper items, much depends on what process the silver is recovered from and how large the batch... 

Some copper things I have used to replace the silver in solution:

Cathode copper, which comes from recovery of silver from silver brazed copper and silver-plated copper, in copper electro-winning copper sulfate cell project

Copper powder, usually at the beginning of the cementing process, and switching to thick solid copper to finish up the reaction, this copper powder is a byproduct of other recovery processes.

Very fine copper wire (finer than human hair) from small transformers, this fine wire after incineration and washing is similar to the powder only finer, and is used like the powder at the beginning to consume the fine copper completely before finishing up with a larger buss bar of copper.

With powder or finer pieces of copper, I only use it in the beginning of the reaction, and make sure all of the fine copper dissolves before all of the silver is cemented out of solution, crushing any clumps and good stirring are important to make sure you do not have bits of copper metal mixed with silver metal cemented powders, (slight excess of free nitric is also helpful) before all of the silver is finished cementing and adding the buss bar to complete the process.

When using just the thick buss bar you will not have to worry about bits of copper mixed with your silver metal you cemented out.

Clean copper plumbing pipe, 1 1/2" to 3" diameter about 6" long split lengthwise (use hack saw or large tin snips), and hammered out flat, lightly sanded, or cleaned with a wire brush (heating with a torch and rinsed off with water just prior to use. Sometimes you will want to cut this slab of copper again to better fit vessels using large tin snips, the larger diameter pipe is easier to cut and open up flat, and is thicker than small pipe would be, the horn of an anvil and a hammer makes easy work of unrolling the copper pipe. I do not like the idea of just smashing the copper smaller piece of pipe flat, although it will work.

Copper electrical wire, grounding-bonding wire in larger diameter, or sometimes even 10AWG for cementing small batches.

Copper arms from contactors or breakers, many times these will have some silver or silver plating, I only use the larger heavier pieces.

Silver-plated copper dinnerware (if using this be sure its copper and not brass or a white metal)...


1 gram of copper will cement 3.4 grams of silver, I am guessing I could sell my scrap copper at about $2.50 per pound (453.5g), silver around $20.00 per troy ounce (31g), so if I cemented 3.4g of silver for every gram of copper in that pound of copper worth $2.50, I could cement 1541.7 grams of silver, or about 49.7 troy ounces of silver.
So I could sell my scrap copper for $2.5o, or cement silver with it and get about $994.7 worth of silver (darn I wish I had that much silver nitrate, I would be out there dissolving a copper buss bar right now).

Now, if you over used your nitric acid, or did not completely consume the acid, you would use more copper than needed, reacting the free nitric acid (in your silver nitrate) just to dissolve copper into solution instead of cementing silver, nitric is not cheap or easy for me to get, so I am careful of with my use of HNO3, whether I buy it or distill my own.

About 1.2ml of 70% HNO3 diluted with equal volumes of water will dissolve a gram of silver, and it takes about 3.4 times this much nitric to dissolve a gram of copper.

To state this backwards a gram of copper would consume about 4.15ml of excess HNO3 in your silver nitrate solution, so if you do not get too carried away with your use of nitric acid when putting the silver into solution, and use heat to be more wise with its use, it would not take much copper at all above the needed amount to cement your silver, although we do want to be sure the solution is slightly acidic when we cement silver, we do not need large amounts of free nitric in the silver nitrate solution.

If silver nitrate is too concentrated, especially with more copper nitrate already in solution the cementing process is more slow or difficult, than when solutions are more dilute.

The copper nitrate by product I can use in many different recovery operations, or convert it to another form of copper salts for use, and actually I will eventually get my pound of copper metal back, so the that buss bar (or the tiny portion of it that dissolved, I do not have enough silver to dissolve the whole 1# bar) was not wasted in the process of cementing silver.

I actually hate dealing with silver chloride, I am not that fond of the conversion methods, But I do seem to find myself with silver chloride much more often than I would like, mostly from recovery processes where I cannot use, or do not want to waste my nitric acid, I not only feel dealing with silver chloride is troublesome, and easier to loose silver in the processes, more trouble melting back to silver, 
I do not get excited at the reaction of making silver chloride, or converting it.

Cementing silver with copper is always just plain exciting to me, and melting silver metal from the silver cement is another pleasure. 

I am very tired, rambling again

Edited, (after a few hours of sleep), I meant to say silver nitrate where I said chloride, The ratio numbers (I am not good at remembering) and have made notes, these numbers do vary a little, but the Numbers I got from GSP have served me very well.

Actually when it comes to numbers, silver, and learning to recover or refine precious metals, GSP's posts have been, and are still invaluable to the success of the forum and to the members here who wished to learn this art.
I recommend reading GSP's posts, his well written book, all of the information he has provided, and his equations (many of which I still cannot compute).

The forum and its members, owe Chris (Gold Silver Pro) a giant Thank-You, for our success and education.


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## bswartzwelder (Sep 17, 2013)

Butcher,

You say rambling, but what I hear is educating. I have not read every post on the forum. I started with the "Data" section and read almost everything. Then I moved to the "Types of PM Scrap" and "Where to Find Scrap" sections, but didn't finish them. I read the "Safety" section in its entirety, and skimmed the "Chemicals" and "Legal Things".

The entire "Processes" section has been my favorite. Lately, after I catch up with new posts here, I often go to one of the sections I have not finished and start reading unread posts. I have yet to have a day when I haven't learned something. 

I purchased C. M. Hoke in hardcover and read it when I'm processing something outside. I would like to see someone rewrite Ms. Hokes book and add a little more specificity to her reactions. Instead of a pinch of this and a spoon of that, it would be nice to see it more like how you and other members on the forum explain thing. "It takes X grams of Y to react with Z grams of this solution and you can expect to recover W grams of PM A. I know that with all the variables we deal with, the numbers would most likely be off (even by quite a bit), but it would help with a starting point. She also doesn't mention what pH to expect when adjusting solutions. It would be my guess that although pH meters hadn't been invented yet, and possibly not even pH test strips, but a rewrite of he book including those items might be a worthwhile project. This forum is filled with C. M. Hokes and we all owe you guys a debt of gratitude for your time and efforts.


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## Platdigger (Sep 17, 2013)

Butcher, you said "Any time I can, my choice is to cement the silver from silver chloride solution with copper metal."

I am sure you meant to say "nitrate" solution. You must have been tired... 8)


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## goldsilverpro (Sep 17, 2013)

These are the dissolving numbers I use. They are easy to memorize. They are only ball park numbers but being more precise is usually a big waste of time since I never know exactly how much I'll need. I only use these numbers to get an idea of how much I MIGHT need. I find out how much I REALLY need as the dissolving is progressing.

One gallon of 70% nitric will dissolve about 100 tr.oz. (about 7 pounds) of silver. 

A gallon of nitric will dissolve about 2 pounds of copper or many other common base metals. 

A gallon of aqua regia will dissolve about 2 pounds of gold or about 2 pounds of many common base metals - copper, iron, etc.


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## butcher (Sep 17, 2013)

Thank You Chris (GSP), (for the numbers), and for everything you have done for the forum, its members, and the world, thank you your sharing your education, Your time, and help.
The forum and the world are in debt to you, for your help has increased its education, you have also helped to insure the ability of common man to gain an understanding of precious metals, something not many in history have done. 

I do not know how to say how important you are to all of us...
But I can say
THANK YOU. 

(PS:edited the rambling above).


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