# Not so fine silver



## mnap89 (Nov 27, 2010)

Hi there
Im a jeweller and Im mostly making in silver. About three months ago I bought 100 grams of fine silver from my supplier - they always sold good quality silver. So I bought that silver and didnt used it since last week, because I got many sterling scrap that I use. So when I used all of my scrap silver I made some new sterling alloy using fine silver that I bought. So I melted it, added proper ammount of copper and cast an ingot. Rolled it, and annealed. Air pocked showed up. So I cast it again and same thing happend. I have made new alloy, but air pocked were there too. I was casting ingots from some time but never have air pockets before. So I made couple of new alloys, melted with and without borax but air pockets were there all the time. So I added some argoflux - a reducing compound that improves fluidyty of molten silver, prevents oxidation of copper and reduces chances of trapping air in metal. But that didnt helped much. So I tried using new crucible - but that didnt helped too. I have used almost all of my oxygen and propane by melting ... 
But to the point. I think that my fine silver is not so fine as it should be. I have took some of sterling that I made using that fine silver and tried to refine it(I have refined my silver scrap from copper/silver mokume-gane without any problems). So I dissolved it in 30% nitric acid, few black and yellow particles has shown up in acid, so I filtered solution. To get silver chloride Im using pure sodium chloride dissolver in hot water that I add to silver nitrate solution. When it stops making white clouds, I add few drops of 36% hydrochloric acid to get all silver nitrate turned to silver chloride. Then I pour of liquid and wash silver chloride with hot water about 5-6 times. Then I cover silver chloride with 20% hydrochloric acid and add pure zinc. As zinc dissolves chloride changes to silver - it has grey colour. Then I wash silver with hot water about 5-6 times, then dry It and melt in crucible. I am using this method to refine my silver scrap and got good quality of sine silver (checked in hallmaking office).

As I was saying, I have refined sterling silver (made using doubt quality fine silver) using method described before But I think it have quality same as fine silver that I bought.

So I made a little test for purity of silver.
I took three samples of fine silver 
1)some old fine silver(it was refined some time ago from copper/silver mokume scrap)
2)refined sterling silver(alloy was made from bought fine silver and copper)
3)fine silver that is doubt quality

I have melted these three smaples on my soldering board and let them soldify. sample 2 and 3 left some white stain on my soldering board, sample 1 didnt.
Also sample 2 and 3 have little waves on its whole surface - because they have some impurities in them. 2 surface is slightly smotther.
Sample 1 have about 10-20% surface covered with these little waves - so it have some impurities but much less then sample 2 and 3. Rest of sample 1 surface is smooth and bright as it should be.
All three pieces are bight and white colour - so they dont contain copper.
As you melt fine silver it absorbs air, and when it cools it gives that air back, thus giving sounds - like braking little bubbles. As fine silver soldifies it should have little vulcano-like shapes on its surface - because as it soldifies, thin skin forms on its surface and as air wants to escpae from molten silver inside it breakes that skin and leaves little vulcano-like shapes on it surface.
Sample 1 has these vulcanos. 2 has only few little vulcanos - but htey are really small. 3 has 0 of these.

Here is a picture of these three smaples: left 1(old fine silver refined from mokume), middle 2(fine silver recently refined from sterling made of last bought fine silver), right 3(corrupted quallity fine silver that I bought last time).







So Refining didnt improved silver quality. When I made alloy using it it still have air pockets in it. So what should I do?
I think that If I refine it once more it could be better quality and that would solve problem or air pockets in my ingots. But how should I do it? Refine it in same manner that before? Or should I do electrolisys? Or maybe I shoud refine it using method that I have read over this forum. It was something like dissolivng silver in nitric acid, then evaporing acid to get silver nitrate crystals, then dissoling it in destilled water, evaporating again, then heating silver nitrate crystals up to 440*C, and dissolving in destilled water, any particles left and impurities, so filtering sollution, evaporating and so on.

My fine silver should be good quality just for making new alloys and these alloy shoud be good quality so I can make jewellry with it.
And air pockets are not result of bad casting, bad melting etc. Im am doing everything as always. I am sure it is something im fine silver that I bought last time. because as it is melting on soldering board it leaves white stain on it, dont have smooth surface and vulcano-like shapes.

Looking forward for your advices.
Cheers, mark


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## qst42know (Nov 27, 2010)

Refining silver with chloride can carry lead chloride through the process.


It is possible you aren't getting all the zinc out, you can reduce the chloride with sodium hydroxide NaOH.

Electrolytic silver cell would produce the best purity. And valuable metals can be recovered from the anode slimes.


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## mnap89 (Nov 27, 2010)

I dont have any lead in my workshop, so I dont think it would cause this problem. But it can be true because fine silver that I bought is already corrupted. So I need to try getting lead out using sulphuric acid. 
I dont hink that zinc could be the problem. Because Im using silver/copper/zinc solders when I make jewelry. Sometimes I put few small pieces with solder when Im melting my scrap and it never caused any problems.
Also when im turning silver chloride to silver using hydrochloric acid and zinc, I wait until all chloride is uniform grey colour, Then I add just a little more zinc just to make sure cholride is completly turned into silver, when sollution stop bubbling it mean all of zinc has dissolved but to make sure I add some 36% hyrdochloric acid, stir it and see if bubbles appear. If no it means all zinc is in acid. then I pour of acid and wash silver. I always did it that way and it never caused any problems.
I still would like to hear more opinions about how to solve that problem before I start do do anything.
All information is valuable.
Cheers, Mark


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## qst42know (Nov 27, 2010)

The white smoke residue from your melt is possibly silver chloride, formed while acid washing away the zinc. Silver chloride can cause melt troubles. 

Does your melt flux include any soda ash? It can help reduce silver chloride.

Electrolytic silver cell is the recognized method to produce the purest silver and your reward could be platinum group metals in the anode bag.

It's all here on the forum. 8)


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## mnap89 (Nov 27, 2010)

What makes you think its silver chloride?
When I got my silver chloride I cover it with hydrochloric acid and then add zin to change chloride to silver. You say when I add hydrochloric acid, silver chloride dissolves in acid, and after zinc is dissolved silver chloride settles back?
If its true that I have silver chloride in silver that I refined, then how it is possible to silver chloride be in fine silver from supplier?
I dont add nothing when I melt fine silver. But maybe I should. you say soda ash? I will see if I have some, and maybe I will try that.
Last time when I was refininf mokume scrap, I dissolved it, get silver chloride, and turned it to silver by hydrochloric acid and zinc it was fine. no white stain on soldering board, air pockets in ingots, etc.
But if what you say is true, if my refined silver contains silver chloride, then if I would dissolve it in nitric acid, silver chloride that was in silver should appear on the bottom since it cant be dissolved in nitric acid.


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## qst42know (Nov 27, 2010)

I would expect some silver chloride to form when you add HCL to your zinc reduced silver. That's why reducing with NaOH would give a cleaner silver.

If you are not using a silver cell to finish refining you should get some benefit from using a good flux recipe.


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## mnap89 (Nov 27, 2010)

I dont thing what you saying is possible. If you reduce silver chloride with zinc, it become silver and it cant be dissolved in HCl. Silver chloride froms if you add HCl or NaCl to silver nitrate, but not when you add HCl to silver.
Or maybe I dont know something?
Could you tell me more about reducing silver chloride with NaOH method?


Lou said:


> A test for purity: take a sample of pure silver powder and dissolve it in quality nitric acid. Note if there is ANY color whatsoever to the solution--it should be colorless. Evaporate this (still watch color) to dryness and heat in a porcelain dish to 440*C. Cool this and dissolve in hot distilled water and look for any sediment on the bottom. Sediment on the bottom indicates metal oxides that formed during the fusion of the silver nitrate at 440C...just about every impurity will form an oxide at that temperature. No oxides and no color mean that your silver is over 99,995% pure.
> 
> This procedure can be repeated and high quality reagents used to yield silver that is factors of ten more pure. Eventually, however, there comes a point where Ksp and solution equilibria put a cap on what ultimate level of purity you can get. Just think, 107g of silver, roughly a mole, contains 6.02214 X 10^23 atoms. Even if your silver were 99,9999999% pure you would still have a large number of other atoms!! There is interesting chemistry behind the purification of metals, both from the analytic and from the physical standpoint!


Can you use this method to refine you silver after it has been refined dissolving in nitric acid and reducing from silver chloride?


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## qst42know (Nov 27, 2010)

It is silver chloride that is the impervious layer on silver.

If you can access lazersteve's video it explains the NaOH reduction process better than words.

http://www.goldrecovery.us/


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## mnap89 (Nov 27, 2010)

If I dissolve silver in nitric acid and then add to it sulphuric acid, white particles appear. is it lead sulphate or silver chloride?


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## qst42know (Nov 27, 2010)

Hello mnap89 

I owe you and everyone else that read this an appology, I tested this myself. And went and checked. Sulfuric acid is not for silver nitrate solutions. Silver sulfate is the result. It does not remove lead, lead also reports to the bottom as sulfate.

Hot water rinses are the correct solution for lead chloride in silver chloride.

When the experts quit laughing I'm sure they can be more help.


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## mnap89 (Nov 28, 2010)

If you add sulphuric acid to silver nitrate that may contain lead, it will form lead sulphate and silver sulphare, but you can add water and silver sulphate will dissolve and lead will stay on the bottom, is that correct?
From what I heard if you make silver chloride and there is lead chloride too you have to rinse with hot wate so lead chloride will dissolve in hot water. but what temperature that water should have, and when do you know that there is no more lead there?
There was somewhere on this forum that if you have silver and lead chloride in your sollution you should add amonia water and silver chloride will dissolve, but lead chloride will remain on the bottom, so you can filtrate it. And after you left lead behind you add HCl and silver chloride will appear again, but can you add hot sollution of NaCl and water with same effect? Is this method correct or I missed something?
Is it possible to use Ammonium bicarbonate instead amonia water? From what you can read over the internet, as you heat Ammonium bicarbonate up to 60*C it decompose for amonia (gas), water and CO2(gas). So there will be some amonia in you solution, so it should react with silver chloride and dissolve it. Tell me if Im wrong.


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## qst42know (Nov 28, 2010)

Silver sulfate is only minimally soluble in water.

Lead is only one of many possible contaminates.

The only certain way is the silver cell.

Consider buying your material from a source that does use a cell. 

Unless you find platinum or palladium in this silver and then buy all they have.


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## mnap89 (Nov 28, 2010)

Ok I am thinking about doing some electrolisys to refine my silver.
Can I use graphite rod for cathode, or should it be stainless steel or only fine silver?


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## lazersteve (Nov 28, 2010)

mnap89 said:


> Ok I am thinking about doing some electrolisys to refine my silver.
> Can I use graphite rod for cathode, or should it be stainless steel or only fine silver?



You'll want a rectangular piece of graphite for the cathode, not a rod. The other materials you mentioned will work also. The soft graphite will tend to decay over time so get the hard kind. 

Steve


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## mnap89 (Nov 28, 2010)

Is it important to have rectagular cathode? I know that it will have bigge surface so silver will deposit faster, right?
Ok I was watching a video on youtube on silver refining, and there was shown that you shoud use not less then 0,8 volt and not more then 4 volt. Dont remeber about amperage. but could someone tell me about these things? Im planning to refine small pieces up to 3 oz maybe, but mostly 1 oz at time.


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## Palladium (Nov 28, 2010)

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=39&t=2919


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## aflacglobal (Nov 29, 2010)

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=39&t=5195

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=3940

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=732&p=6603#p6603


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## mnap89 (Nov 29, 2010)

I have read these topics. 
But I dont understand how much amperage I should have... I know about hte voltage should be somewhere abou 1-3 but what with amperage? Will 5A work? 
From what I have read, Voltage affects crystal size, and you need right voltage to get only silver plated out. But what is with amperage? Bigger amperage - more sillver deposit on cathode in less time, right? But you can run silver cell with 0,1 A and with 40 A, right? It only changes ammount of silver plated on cathoder in cetrain time. Is that right?
So what should I use for my power supply?


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## HAuCl4 (Nov 29, 2010)

mnap89 said:


> Lou said:
> 
> 
> > A test for purity: take a sample of pure silver powder and dissolve it in quality nitric acid. Note if there is ANY color whatsoever to the solution--it should be colorless. *Evaporate this (still watch color) to dryness and heat in a porcelain dish to 440*C. Cool this and dissolve in hot distilled water and look for any sediment on the bottom. Sediment on the bottom indicates metal oxides that formed during the fusion of the silver nitrate at 440C...just about every impurity will form an oxide at that temperature.* No oxides and no color mean that your silver is over 99,995% pure.
> ...



So simple that it'll likely be overlooked as a refining method. No reagents, only heat and water used. Done in a closed system the nitric acid can be easily recovered too. Nice post Lou!.


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## mnap89 (Nov 29, 2010)

Can I use power supply from my PC as power supply for silver cell? It have 3,3V up to 14A output.
Will it give good results?


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## Barren Realms 007 (Nov 29, 2010)

Yes you can use it on a small one with fair results.


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## mnap89 (Nov 29, 2010)

Thanks.
Right now I made some silver nitrate. Its almost dry now. But I can see that there is just a little blue crystals. It must be copper nitrate. But there is just a little bit of it. Is it ok if I make electrolyte from it? I have seen somewhere that elecrtolyte should be made only silver nitrate but I have seen sources that say that it also should have few drops os nitric acid. Which is correct? If you add nitric acid it will dissolve your fine silver ad it deposits on the cathode. It will be slow process but it will.
And can someone tell me more about Lou mentioned before about rising purity ot silver nitrate by heating and dissolving it? It was said that it should be heated to 440*C in porcelain dish. Silver nitrate should fuse and impurities should oxidise thus making them insoluble.
Can you use standard coffe mug for this procedure? And How do I know that I have reached 440*C? Will silver nitrate crystals melt into on big crystal or what? Should I use electric kiln for that purpose or can you do it using hot plate or oxy/propane torch?
Can you use coffe filters for anode bag?


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## butcher (Nov 29, 2010)

I have not used a silver cell in this fashion so take a grain salt with the information I post here. (Poster’s inexperience in this field).

The silver nitrate electrolyte (liquid) can have some excess nitric acid, the silver nitrate solution will only hold so much silver depending on temperature and other factors, the fairly pure silver anode is not dissolved without applied external current once the silver nitrate solution holds as much silver Ions as it can, but apply an external current with your power supply, the now then the NO3 negative (anion) moves to the silver anode, and dissolves the elemental metal into solution (oxidization)(loss of electron), and the invisible (clear in solution)silver positive Ion in solution (cat ion) moves to the cathode (gains an electron)(reduction) and plates out to the cathode as the silver crystal we can see,

Copper in the electrolyte, some I understand can be beneficial, but up to a certain limit, then it can start to contaminate your pure silver crystals at the cathode, there are ways to deal with this, do not have copper in anode or solution above the limit, or removing a portion of the heavy laden copper electrolyte and replace this portion of electrolyte with only purer silver nitrate,

I believe stainless steel can be used as a cathode I can be wrong. You want a large surface area for cathode. A pure silver cathode can also be used.

There is a ton of information on the silver cell types and usage on the forum, a little studying will give you everything you need to get this project up and running, this information has been posted in great detail, by some of the best in the bussiness, reading will give you more chance of success than asking a few questions and jumping into it. we cannot burden our pro's to explain all this over again, we will need their time to get us out of a bind with the project after we do our homework.

440 degrees C is greater than 800 degrees fehrenheight, I do not think your coffee cup will hold up.
A hotplate will not reach those temperatures.
fuse is not melting they are different fusing can make salts soluble but not melt to metal, looks like he is just below the temperature needed to melt into metal.this would be hard to achive with a torch, or a controlled enviroment like a furnace with good temperature control.
I do not see where you need this procedure in refining your silver, I would dissolve silver in nitric let settle decant and filter then cement silver with copper, wash ,melt silver to anode form, read up on silver cells, you will see the muslin cloth, anode candlestick, cell construction, and much more, I would do this instead of using a coffee filter.


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## g_axelsson (Nov 29, 2010)

Would it be so bad to just cement the silver onto copper? PGM:s would follow the silver but zinc and lead would stay in solution. Some copper would also add to the silver by drag down, but the silver were ment to be alloyed with copper anyhow.

/Göran


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## mnap89 (Nov 30, 2010)

According to wikipedia. Lead chloride is soluble in amonia, silver chloride is soluble to amonia too. So I think that trying to separate silver chloride from lead chloride isnt the best idea because some of the lead chloride will dissolve too.


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## Barren Realms 007 (Nov 30, 2010)

mnap89 said:


> According to wikipedia. Lead chloride is soluble in amonia, silver chloride is soluble to amonia too. So I think that trying to separate silver chloride from lead chloride isnt the best idea because some of the lead chloride will dissolve too.



If you follow the recomended procedures of boiling you gold powder in water to remove the lead before you use ammonia this is a mute point and needs no discussion.


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## TK Rose (Dec 1, 2010)

qst42know said:


> The white smoke residue from your melt is possibly silver chloride, formed while acid washing away the zinc. Silver chloride can cause melt troubles.



I believe the white smoke and residue is carried over zinc, i.e. zinc oxide, the same stuff lifeguards smear on their noses.
It also causes those bubbles, Zn boils at 1664°F a mere 24°F hotter than Sterling's melt temp. and 97°F cooler than pure Ag's melt temperature. 
Just one of the disadvantages of cementing with zinc, especially Zn dust or shot, you are bound to get carry over of small particles of metallic Zn, as well as zinc chloride if cementing in HCl solution, ZnCl2 decomposes into zinc oxide (see above) and chlorine.


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## goldsilverpro (Dec 1, 2010)

Silver chloride melts at 851 F and gives off white smoke at a temp. of much less than 1664 F.


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## mnap89 (Dec 2, 2010)

I dont think it could be silver chloride or zinc. If it would be zinc of sivler chlorie it would be really small ammount. And when melting it would burn away. I can melt it 5 times and there is still the same effect. I suppose it is lead. it doesnt burn away so easy. Zinc doesnt affect your alloy working properties - lead does. It must be lead.
You say that electrolisys is to best way to refine my silver, right?


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## butcher (Dec 3, 2010)

I believe electrolysis refining of silver would be the best choice.


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## mnap89 (Jan 14, 2011)

I have tried refining silver by electrolisys. I have used rechargable batteries just for test. It worked, but the process was really slow. I have used 2,4V and got about 0,2A... Anode was about 20g of 98-99% silver and cathode was fine silver. anode was just a simple button, cathode was about 5x4cm sheet. electrolite was 25g of silver nitrate per 1l of destilled water and few drops of nitric acid.
Using batteries is not the best idea, so I am thinking about using power supply from pc it have 3,3V 10A output, so it could work for refining silver, dont you think?
Or another thing is adjustable power supply.




you can get many types of these. 0-15V or 0-30V, but I think 0-15V would be just fine. 0-2, 0-3, 0-5, 0-10 or 0-20A. Do you think that 0-5A would do the job?
Or the best choice would be building your own power supply?

BTW, here is a photo of my refining.





Cheers, mark


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## stihl88 (Jan 14, 2011)

The best is certainly the Adjustable Power supply you have posted above, especially with adjustable current.

I just bought one myself and i'm kicking myself as to why ive never owned one up until now.
My one will supply up to 16v and 30 amps but does not have adjustable current/amp output
as this is automatic. If i wanted adjustable current output i would have paid a fortune for a 
high current model.

I am using my power supply to power an HHO generator & HHO Torch setup, ive nearly finished the HHO
generator and will post pics of it here on the forum once i get it up and running. I'm hoping for about 3Lpm
HHO output from this generator...


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## rbramsey (Jan 14, 2011)

I use a computer power supply for my cell. Most current P/S have 3.3V @20A or more. I prefer the ones with a power switch in the back but it is not necessary. 3.3V works well as I can see. I ran 8.3ozt of once refined silver with one of Steve's graphite cathodes in about 2 days or so. The electrolyte was 100g/l of silver. 

I am toying with the an idea to modify the P/S to add current limiting, also take the 12V output and turn it into a 0-12V variable output. 

Richard

I have a question about the electrolyte while its on my mind. Is there a balanced (for a lack of a better word) load for the amount of silver in the electrolyte? If I start with a solution of 50g/l will the cell try to balance the electrolyte to say 100g/l before it starts to plate out silver. Or is the set when the power is added? Can I increase the silver content to 200g/l to create more of current draw to plate faster. This part of the cell I don't quite understand how it works. I hope this is clear enough to understand.


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## lazersteve (Jan 15, 2011)

The more silver nitrate in the electrolyte the more conductive it is. 

The amount of nitric in the electrolyte determines how much silver will be dissolved in the electrolyte. For every silver atom that goes into the electrolyte from the anode, another plates out on the cathode. The number of silver atoms in the electrolyte remains constant barring any copper or other contamination that gets in the electrolyte.

Steve


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## mnap89 (Jan 15, 2011)

Thanks for reply guys,

So for now, I will use PC power supply, and when I get some cash, I will buy 0-15V 0-20A adjustable power supply.
Another good thing aboud adjustable power supply is that you can use it to make things, like refining silver, refining gold, plating etc. you just have to set up correct voltage and amperage.

Cheers, mark


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