# Removing impurities



## Chaos (Feb 2, 2010)

Hello all,
I've got a question and was hoping someone could lend a little of their expertise~
Recently, I purchased a smelter (110 V, 2200 deg max, 1kg...same ones for sale on Ebay)
I got some silver scrap to go along with it (some of which the previous owner, a good friend, had already melted into blocks)
He told me everything that went into the blocks was sterling~
Yet, when I did an acid test on it, the drop turned brown instead of blood red (indicating approx. 80% silver)
I tested all over the block with the same results...
My question: What is the best way to extract any impurities from the block?

A separate question: How would one tell the difference between .925 and .999 silver (acid test reveals .925 and .999 the same)

Thanks for your help,

Jamie


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## Harold_V (Feb 2, 2010)

Chaos said:


> My question: What is the best way to extract any impurities from the block?


You can't. However, you can dissolve the entire block, then selectively recover the silver contained within. You can dissolve the block with dilute nitric acid. Recovering the silver would be accomplished by cementing with copper, or you could go the hard route and precipitate the silver as a chloride (common table salt works well, or you can use HCl). If you choose to dissolve the block in order to extract the silver, melting and pouring to shot (corn flakes) will accelerate dissolution. 



> A separate question: How would one tell the difference between .925 and .999 silver (acid test reveals .925 and .999 the same)


There are subtle differences when testing with Schwerter's solution. The initial reaction may be the same, but given time, the pure silver will stay red, while the alloyed silver test will darken. The test works by dissolving traces of the metal in question. If there is copper present, it will eventually show it's color. 

There's a simple way to test if you can dissolve a trace of the item in question. Pure silver will yield a solution that is all but absent of color. If the resulting solution leans towards green, in spite of being very light in color, that's a sure sign you have some copper present. To verify your finding, add a drop of ammonium hydroxide to a drop of the solution (use a spot plate). If there is copper or nickel present, the familiar blue color will develop. If it's important for you to know whether you are seeing nickel or copper, the addition of a drop of DMG will shift the blue color to pink if you have nickel. If the addition of DMG makes no difference, you have copper. 

Likely not what you wanted to know, but all of this can be very useful when you're trying to determine what metals you have present. 

Harold


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## Chaos (Feb 2, 2010)

Harold,
Thanks 4 the reply!
If you don't care, I had one more question:
What is your opinion on buying weighted silver items on Ebay?
Keep in mind, my purpose is to extract at least .925 pure from the items so I can melt them down and sell the resulting bars for a small profit~
How are the items generally weighted (lead up inside candle holders for example...or is the weighted feature mixed as an alloy)?
Just wondering how easy it would be to remove the unwanted material~

Jamie


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## jimdoc (Feb 2, 2010)

I don't see how you can make a profit by melting marked sterling silver items into an unmarked bar or ingot, especially keeping it at the same purity. Then you have to figure in that the weighted items, that I guess you will be buying, have an unknown amount of junk in them.
How would you factor that in, unless you are getting them free or very cheap, it is a total gamble. Weighted silver needs to be peeled, or cut away away from the weighted section.Bottom line is; I think the marked sterling scrap will be easier to sell than your unknown bar or ingot.
Jim


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## Harold_V (Feb 3, 2010)

Chaos said:


> Harold,
> Thanks 4 the reply!
> If you don't care, I had one more question:
> What is your opinion on buying weighted silver items on Ebay?


Simple. Don't do it. 

Have you experienced filled sterling yet? It varies beyond belief. You'll have no way of knowing the value, for the weight of the object will not reflect, in a meaningful way, what it may contain. They are rosin or cement filled, often with steel bits to act as stiffeners. Some have an exceedingly thin skin, while others have one slightly heavier. In my experience, the typical filled sterling piece might yield less than an ounce. Think of a simple candle holder for an example. 

If you think you can buy sterling and make a profit, make it your hobby, and don't quit your day job. I refined silver as a service to my customers, due to the fact that it was silver I chose to use for inquartation in my gold refining service. I charged 20% for refining silver, and do not consider myself as having made a profit. This was long ago, when silver was far more available, and at a reduced price as compared to today. I also was paying only $4/gallon for nitric acid. 

Said another way, if you think you can make a few fast bucks dealing with silver, I see a dismal outcome for you. It's just not a cash cow the way you may think it to be.

Harold


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## bid_slayer88 (Feb 12, 2010)

I'am sorta in the same boat as Chaos. I have some " pure sliver " bars bought from a rather shaddy seller the price was ooooh soo to good but it was clear that it was silver and at the same time very clear not pure silver I figured at most 50 % purity. I heard read that nitric acid will take care of my problems then put copper in the soultion and all is well. well if I understand soo far corect ....that nitric acid acts with silver and copper the same right? soooo what if these silver bars are split with copper and I melt the bars with nitric acid? because even my hope-less chemistrey mind knows that .5 silver/.5 copper desolved with nitric acid and add a copper object and get pure silver clingging to it won't happen? am I going wrong some were ? little help please ...any thanx :?:


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## Harold_V (Feb 13, 2010)

Ok, lets start with correct terminology. One does not "melt" with nitric, one "dissolves" with nitric. Melting is a heat process, unlike dissolving. 
As far as your question goes, it is true that silver and copper will both dissolve in nitric acid, particularly dilute nitric. Something about the hydronium ion that is rarely discussed. It is always desirable to dilute your nitric for this purpose, even when dissolving pure silver for making electrolyte. 

Once you have both metals in solution, the copper contained within does not cement silver. Elemental copper will, providing the required electron that allows silver to leave the solution and the added copper to enter. This process is totally effective and will recover, for all practical purposes, 100% of your silver, leaving the vast majority of copper behind. It just takes time. The greater the surface area you provide (copper), the faster will be the recovery. If there is an abundance of silver present as cement (that's what one calls the recovered silver), it pays to agitate it a couple times, to free any trapped silver nitrate, allowing it to interact with the added copper and to be recovered as cement silver. Simple as that. 

When all of the silver is down (you can test by removing a drop of blue solution and testing with either table salt or HCl. If a white cloud forms, there is still silver present), the copper should be removed, the silver allowed to settle well, then the blue solution decanted. The silver should then be washed several times with water to remove all traces of dissolved base metals. At this stage of recovery, tap water is perfectly acceptable. When it is clean and has dried, it can be melted to create an anode, which would then be parted in a silver cell. 

Following the above procedure, you should be able to recover silver (by cementing with copper) that is about 99% pure. If there are traces of platinum or palladium present, given enough time, they, too, will be cemented by the copper. For that reason, it's always a good idea to part the silver to achiever higher purity. That not only recovers the included values, which can include gold, but insures that you market silver of good quality. 

Harold


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## Refiner232121 (Feb 13, 2010)

If I had coin silver I would dissolve this in dilute nitric acid.
I went on Steves web site to learn about cementing with copper.



> Here i have silver and copper nitrate from inquatating that ive done
> just recently
> its about 2 cups liquid
> i also have a small section of a copper pipe and i have a string with 2 loops in eithere end



What I would like to know is what is the next process after the silver is diluted in nitric acid.
If you dip in a copper pipe in that solution the pipe will disslove.
Can someone tell me what step I am missing 
Do I have to dilute this solution before dipping in the copper pipe


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## Refiner232121 (Feb 13, 2010)

From reading a few other threads I am thinking that I have to dilute the silvernitrate with water befor cementing with copper wire.
If that is true how much water do I have to add 
Because Harold was saying that a bit of nitric acid in that solution is good to have


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## Barren Realms 007 (Feb 13, 2010)

Refiner232121 said:


> If I had coin silver I would dissolve this in dilute nitric acid.
> I went on Steves web site to learn about cementing with copper.
> 
> What I would like to know is what is the next process after the silver is diluted in nitric acid.
> ...



You are just not catching what is happening. The silver that is contained in the solution is cemented out when the copper bar is added, the copper that is in the solution stays in solution. Dilute nitric works better than pure nitirc to disolve the original silver, with some heat added.



> Harold wrote
> 
> Once you have both metals in solution, the copper contained within does not cement silver. Elemental copper will, providing the required electron that allows silver to leave the solution and the added copper to enter. This process is totally effective and will recover, for all practical purposes, 100% of your silver, leaving the vast majority of copper behind. It just takes time. The greater the surface area you provide (copper), the faster will be the recovery. If there is an abundance of silver present as cement (that's what one calls the recovered silver), it pays to agitate it a couple times, to free any trapped silver nitrate, allowing it to interact with the added copper and to be recovered as cement silver. Simple as that.


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## bid_slayer88 (Feb 13, 2010)

thanks Harold_v makes lot more sense now.


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