# Dissolving Ag with nitric - quick recap please?



## Bushka (Dec 1, 2013)

Hi. I posted a lot here about a year ago when I was trying to process about 1000 g of old, hard silver chloride. Without going into a long story, I wonder if anybody can help me with two questions:

1. I have a bottle of 50% v/v (50% by volume nitric/water) nitric acid. How much of this solution is needed to dissolve a gram or an ounce of silver?

2. I do not currently have a good means of heating the solution outdoors. Will the nitric convert the silver to solution when cold, but just over a much longer time frame, or do I need to heat the nitric to get the silver into solution?

I am fully aware of the hazards of using nitric acid.

Thanks for any help!

Dan


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## torscot (Dec 1, 2013)

Hi Dan,

If you're trying to dissolve silver chloride with nitric, ("old, hard silver chloride") you're going to waste your nitric. Silver chloride is not soluble in nitric. It won't work. What you have to do is get that hard lumpy chloride as fine as you an get it POWDERED. Mortar and pestil, (or steal the wife's food processor. You may have to replace it though, she may not like the idea) Fine, fine powder. This step's optional. Mix the chloride with 1.5 times the volume with water. then add ammonium hydroxide, 28% ammonia and water, it's available on ebay in 1 litre bottles. This will take up the chloride in a coodination complex. and leave impurities. these impurities might be actual silver, as exposure to light causes silver chloride to turn to silver again. SO DON'T THROW THEM AWAY. Destroy the complex by adding HCI Your silver will drop out again as PURE silver chloride, Nice and white, pure and clumpy, ready to convert to silver. Rinse many time with water, The last rinse using hot water to remove any copper (bluish tint) from the solution. Keep this chloride out of the light! Now you have really good chloride to convert to silver (no big hard lumps). There are many formulas shown on this site for converting. I have found the best to be the Lye/sugar method. Search the site for this formula it's here many times and no need to repeat here. You can skip the ammonia part if you want and try to convert to silver just with the lye, sugar method, but any large pieces 1mm or bigger +/- are not going to totally convert to silver and when you smelt the silver it will just go up ina white smoke. Your loss. I have done this several times, and all with success. All the info came from this site. Remember. if you are just trying for the first time. test with a small lot. 30-40 grams. It would be a shame to lose 1000gr of chloride. Also silver chloride is not pure silver, I can't remember the percentage off the top of my head. 70+% silver the rest chloride. Good luck. Rob.


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## Bushka (Dec 1, 2013)

Rob - thanks for your comments. I figured I might confuse people by mentioning silver chloride and then silver in the same breath. I tend to write too much so thought I'd try to be more terse. I've already converted most of the AgCl to Ag using various methods including the blender with lye and corn syrup. The problem is that, as you say, it is hard to get the hard AgCl pieces to convert to AgO with the lye. It doesn't help that nobody seems to know whether more AgCl will be converted by lye if you leave it longer, say overnight.

Anyway, my plan was this: I have a bottle of nitric acid (way expensive) that I'm trying to use as efficiently as possible. I have an unknown amount of AgCl impurity in my Ag cemented from lye. My plan is to dissolve the Ag out of the Ag/AgCl mixture leaving just the AgCl behind. I would decant off the nitric/ AgNO3 solution and then add more nitric acid and more Ag/AgCl mix powder to the flask. Basically I'm trying to separate the Ag from the AgCl with the nitric so that I can pulverize and re-lye the more concentrated AgCl. If I have enough nitric acid I should be able to convert all the AgCl to Ag eventually, I would think.

I used to use household ammonia to dissolve AgCl but I have been convinced that messing with ammonia and silver chloride is probably too dangerous (potentially explosive). It also took way too much ammonia, but I suppose 28% would do better, if not fumigate myself first.


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## butcher (Dec 1, 2013)

Bushka,

I may be a bit confused on what you are working with, silver chloride, which has or has not gone through the conversion process?

Much also kind of depends on the state of silver here, AgCl, Ag2O, Ag..
You can have a silver crystals that has an oxidized coating of silver chloride...

I think when you put nitric into that vessel of silver chloride you will be making some aqua regia in solution, a high nitric acid version of the aqua regia, a portion of the Hydrogen from the nitric acid and the chloride salts would form some HCl in solution as the chloride salt is oxidized by the acid, and any silver that may try to go into solution (as silver nitrate) would again precipitate as silver chloride.

I do not think this will work as you have planned.
But I can see where it might assist to change some of the silver powders back to silver chloride.
(I would just save that expensive nitric acid).

But if you have already used the NaOH or the reduction process on this silver chloride batch, you may not just have silver chloride, you could have silver oxide silver chloride and elemental silver..

I am assuming this is mostly silver chloride already gone through the reduction process with glucose and NaOH, I would probably just use sodium carbonate (prolonged low heat at first), and then melt to finish the conversion to silver metal.

Just my thoughts, there are others that can help you make a decision better than I can, I am still a bit confused as to what you have in that jar.
.


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## goldsilverpro (Dec 1, 2013)

If close to pure silver and if it's 70-71% nitric cut 50/50 with water it will take about 2.44ml to dissolve a gram. This would be the worst case in an open top beaker. If the beaker is covered with a watch glass it should take less. Any copper in there will take about 8.3ml/gram. Other nitric soluble metals in the alloy would likely take more nitric than silver does.


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## Bushka (Dec 1, 2013)

Hi butcher. If I dug up my old posts you might remember my situation. You helped me a bit back then, too.

I had a couple of jars of AgCl from a high school lab, which appeared to have some copper salts as a contaminate. I cleaned up the AgCl and dissolved some of it in ammonia and then electrolyzed it with a battery charger to get silver cement. I didn't process much this way because it was too difficult to dissolve the AgCl and I didn't want to mess with ammonia for safety reasons.

After consultation here, I ran all of my AgCl through a blender with NaOH and then syrup. I had no idea how long I needed to blend but just did the best I could. So now I have a batch of cement powder that has an undetermined amount of AgCl in it. I could keep repeating the blender process, but I thought the nitric acid route might be more definitive. Your comment about aqua regia is very interesting. I hadn't thought of that.

My ultimate goal was to drop silver out with copper and then melt and/or just sell the silver powder sometime.

Does any of this information change your view of what I can do with this stuff?

Dan


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## Bushka (Dec 1, 2013)

goldsilverpro said:


> If close to pure silver and if it's 70-71% nitric cut 50/50 with water it will take about 2.44ml to dissolve a gram. This would be the worst case in an open top beaker. If the beaker is covered with a watch glass it should take less. Any copper in there will take about 8.3ml/gram. Other nitric soluble metals in the alloy would likely take more nitric than silver does.



Thanks! Is your 70-71% above by volume as in a v/v percentage? In comparision, my bottle is 50% v/v, not weight/weight or weight/volume (w/w w/v respectively).


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## butcher (Dec 1, 2013)

I would just powder it fine and mix the silver powders with sodium carbonate, bring the heat up slow before melting, the sodium carbonate flux can help to reduce any remaining silver chloride to metal.

It sounds like mostly you have silver, possibly some silver oxide and maybe some unconverted silver chloride, you could use the nitric to dissolve the silver and silver oxide leaving some silver chloride (with the nitric acid).
Me I would save the expensive nitric and just melt the silver as is.

Our Gold Silver Professional may have some better idea's.


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## goldsilverpro (Dec 1, 2013)

Bushka said:


> goldsilverpro said:
> 
> 
> > If close to pure silver and if it's 70-71% nitric cut 50/50 with water it will take about 2.44ml to dissolve a gram. This would be the worst case in an open top beaker. If the beaker is covered with a watch glass it should take less. Any copper in there will take about 8.3ml/gram. Other nitric soluble metals in the alloy would likely take more nitric than silver does.
> ...



Commercial reagent grade nitric is about 70-71%. This is w/w. It sounds your bottle is 70-71% w/w diluted 50/50 (v/v) with water.


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## Westerngs (Dec 1, 2013)

Bushka,

If your ultimate goal is to get silver metal to further process or refine, I would skip the nitric acid step altogether.

From your post you state that you have silver and silver chloride mixed together. I would smelt it. Use boric acid and soda ash for flux, cover smelt with excess soda ash. I would also use some silica sand as all that soda ash will eat up your crucible, silica sand will reduce that corrosion. Smelt at a lower than normal temperature, say somewhere around 1800F.

You will see some smoke, sadly that is silver going up in the air. But doing a cold smelt with excess soda ash cover should limit the silver losses to about 2-3%. That is about a fair trade off to the cost of doing things other ways and you will have silver metal much faster.

Just my opinion.


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## butcher (Dec 1, 2013)

Adding some carbon in the flux and some as a cover over the top may also help in reducing the silver back to metal.


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## Bushka (Dec 8, 2013)

Butcher - Just one more thing about the nitric acid. I was thinking about your post and I'm not sure what you mean about chloride salts. I should have pretty much all silver and silver chloride with some oxides as you say. Where would the chlorides come from to turn the silver nitrate back into silver chloride? If it did convert to silver chloride that may not be a bad thing because then I'd have a wet spongy chloride that I can convert with lye.

I'm still kind of stuck on doing something with this nitric acid because I already have it and might as well use it up. I'm still a little concerned that there are some things in my cement I'm not aware of and if I just cook it up as is I might get an unpleasant surprise. The nitric could help me flush out any unknowns. I'm also trying to do this on a shoestring budget as I don't see myself doing this over and over. I've read here that I can melt silver in a wooden block with I think a propane (or was it nat gas?) torch (the kind you get at Home Depot, and not the higher temp MAPP torch).


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## Bushka (Dec 8, 2013)

goldsilverpro said:


> Bushka said:
> 
> 
> > goldsilverpro said:
> ...



Thank you! That makes sense.


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## Bushka (Dec 8, 2013)

Westerngs said:


> Bushka,
> 
> If your ultimate goal is to get silver metal to further process or refine, I would skip the nitric acid step altogether.
> 
> ...



Thanks. Even though I've read over a lot of posts, and spent a lot of time posting here earlier in the year, I think my learning curve would eat up my silver before I figured out how much of everything to use, and even how to get a low temperature heat. I feel like I'd have a better chance for success if I convert everything to silver first with nitric I already have and then try to melt the cleaner silver. I only have two small crucibles. So either those have to last or I have to use a block of sintered wood.


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## butcher (Dec 8, 2013)

There are several methods to convert the silver chloride to metal, what silver metal powders or silver oxide you have mixed with the silver chloride would not be a problem, one way is with dilute H2SO4 and iron, you can read about this process in Hokes book, or on the forum.

Getting the silver chloride lumps broken up and finely divided is an important step, as well as good stirring to get silver chloride and iron in contact in solution during the conversion process.

Any copper salts or powder involved would also be converted to metal and would show up in the melted silver.


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## Bushka (Dec 9, 2013)

butcher said:


> There are several methods to convert the silver chloride to metal, what silver metal powders or silver oxide you have mixed with the silver chloride would not be a problem, one way is with dilute H2SO4 and iron, you can read about this process in Hokes book, or on the forum.
> 
> Getting the silver chloride lumps broken up and finely divided is an important step, as well as good stirring to get silver chloride and iron in contact in solution during the conversion process.
> 
> Any copper salts or powder involved would also be converted to metal and would show up in the melted silver.



Could you take another look at the question about aqua regia above? I'm wondering after you know a little more about what I have if you still think this is an issue. I don't think I have any Cl salts to contaminate the AgNO3 and turn it back into AgCl. What do you think?


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## niteliteone (Dec 10, 2013)

Bushka said:


> butcher said:
> 
> 
> > There are several methods to convert the silver chloride to metal, what silver metal powders or silver oxide you have mixed with the silver chloride would not be a problem, one way is with dilute H2SO4 and iron, you can read about this process in Hokes book, or on the forum.
> ...


Isn't the "AgCl" a "Cl salt" :?:


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## butcher (Dec 10, 2013)

If I have AgCl, and Ag powders.
I add some HNO3.
The nitric will form some AgNO3, with the silver, now I have Ag+ cations, and NO3- nitrate anions in solution, along with free nitric acid, and the chloride salts of silver chloride (AgCl).
The acid will also form aqua regia in solution, the Hydrogen from my acid will oxidize some of the chloride salts (AgCl or other chlorides in solution) to form HCl in solution, so basically I will form some aqua regia in solution (with a high nitric content).

In solution along the Ag+, NO3-, Cl-, H3O.
Now the newly dissolved silver metal as silver nitrate, will join with free chlorides in solution and precipitate back out as AgCl, until either one of all of the silver cations or free chloride anions are removed from solution, so basically some of the silver metal powders I dissolved into the solution as silver nitrate converts to silver chloride,(again depleting my solution of the chloride anions), I may be left with some silver in solution, as silver nitrate or even gold if it was in the original powders, from here I could add just the correct amount of chlorides to solution as HCl, NaCl, KCl, to provide the needed chloride anions to precipitate remaining silver from solution as AgCl.


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## Bushka (Dec 10, 2013)

butcher said:


> ... The acid will also form aqua regia in solution, the Hydrogen from my acid will oxidize some of the chloride salts (AgCl or other chlorides in solution) to form HCl in solution, so basically I will form some aqua regia in solution (with a high nitric content).
> 
> In solution along the Ag+, NO3-, Cl-, H3O.
> Now the newly dissolved silver metal as silver nitrate, will join with free chlorides in solution and precipitate back out as AgCl ...



My confusion is in where the chloride _in solution_ comes from. My understanding is that AgCl is not at all soluble in acid solutions, aqua regia or not. Am I wrong about this? Also, it seems you are saying that I am likely to have other, more soluble chloride salts as a contaminant and that will contribute to the Cl concentration. Do I have you right on that?

I'm not sure the conversion of AgNO3 back to AgCl is really a problem, actually. My problem is that I am starting out with hard, dry 30 year old AgCl powder that is partially converted to silver. If I dissolve my silver/silver nitrate powder in nitric acid, some will go into solution as silver nitrate and some (probably a small amount) will convert to soft silver chloride. I can keep adding nitric, decanting the spent solution and adding more nitric and powder (cement) until all the silver is either converted into silver nitrate solution or into soft silver chloride. There will also be the hard bits of original silver chloride, but now I can convert the nice soft stuff with lye and then have a pretty pure hard silver chloride to pulverize further and convert as best I can with lye.

I'm not sure why this wouldn't work, other than it probably sounds incredibly tedious to you guys who work with this stuff all the time! :shock: I just see a mess coming if I just try to melt the stuff as is.

Does that make sense?


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## Bushka (Dec 10, 2013)

niteliteone said:


> Isn't the "AgCl" a "Cl salt" :?:



I suppose so, but I was always used to thinking of a salt as a product of an acid/base reaction. I thought Butcher was talking about some other chloride salts rather than AgCl because my understanding is that AgCl will not dissolve in nitric acid. (As mentioned in my other post).

Thanks.


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## butcher (Dec 10, 2013)

The silver chloride will not dissolve to any extent in the nitric acid.
With that said, silver chloride is still a salt of HCl acid and silver (Acid + metal = salt, of that metal and acid), and yes anytime we have chlorides in solution and add an acid we can put some of those chlorides into solution.

This is why we always recommend incineration when changing acids.

Example we have metal chloride salts with some other base metals and gold, and we wish to remove some metals with nitric acid but do not wish to put gold into solution. 
So (I normally use hydroxide was first to remove as much chloride as possible converting most of the metal salts to oxides or hydroxides and rinse with water), then incinerate to remove traces of chlorides and further oxidize base metals, after cooling I can wash the powders, and now I can use nitric acid, without the chance of dissolving gold (from forming aqua regia) as my powders are chloride free.


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## Bushka (Dec 13, 2013)

butcher said:


> Example we have metal chloride salts with some other base metals and gold, and we wish to remove some metals with nitric acid but do not wish to put gold into solution.
> So (I normally use hydroxide was first to remove as much chloride as possible converting most of the metal salts to oxides or hydroxides and rinse with water), then incinerate to remove traces of chlorides and further oxidize base metals, after cooling I can wash the powders, and now I can use nitric acid, without the chance of dissolving gold (from forming aqua regia) as my powders are chloride free.



That's interesting. Hopefully I'll have more time soon to do something with my cement. It's been sitting on my work bench for nearly a year now.

Dan


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