Dry Silver chloride-- Now What??

[Ignatz61]

I have a pound of dry silver chloride I got from a friend. It is has dried out, Is there a simple way to recover the silver from this?
will I get complete recovery or is some of it going to be too expensive to be worth while?

Can I dissolve in Nitric acid?

thanks,

 

[Harold_V]

Now that it has dried, I'd be inclined to suggest it be furnace reduced, using soda ash and borax. You should expect the process to be hard on the furnace and crucible.

Do not fill a crucible to the top, for it will froth considerably before becoming tranquil. Start with no more than roughly ¼ the crucible capacity in volume. That would include the flux.

If you can find it, use anhydrous borax, or borax glass (identical aside from borax glass having been once melted). Neither of them froth up.

Allowing it to dry was a mistake. Silver chloride is not soluble in acids.

You may experience success by dissolving the silver chloride in ammonium hydroxide, then recovering the silver as silver chloride by introducing HCl. Be advised that the ammonium hydroxide solution, if allowed to dry, is very unstable and can explode. Given a choice, I'd opt for the furnace recovery.

Harold

 

[Ignatz61]

Thanks Harold!
It turns out he has 25-35 lbs of this dry silver chloride. I can use the furnace as you suggest. Can I expect complete recovery or is some of it just not going to convert anymore?

Would it be prudent to try the ammonium hydroxide first to try to dissolve as much as possible then, heat the balance of powder that does not dissolve in the ammonia?

I will not let any of it dry once I start. In fact I would like to convert to metalic as soon as possible as we are splitting the proceeds.

I have heeded your advise in the past and things always worked out. I have concentrated on gold plated scrap and I am getting pretty good at recovering and refining the gold from it. Now I need to try my hand at some silver so I look forward to your advise and I will be re-reading many of the silver related posts here on this amazing forum!
Thanks again,
John

 

[4metals]

Melting the chlorides will give off a dense white smoke, nasty stuff. I never processed any silver chlorides that were completely dry but I have done a fair share of silver chlorides that were damp, having air dried before there were enough to melt. Most melts yielded bars of 110 - 150 ounces. The flux and chloride required a #30 crucible.

You can expect about 53 ounces of silver out of every 5 pounds you process. That will be 6 or 7 nasty melts.

The flux I used was 1 part anhydrous borax, 1 part soda ash, and 1 part silica (use diatomaceous earth) mix this mixture with an equal portion of silver chloride.

Considering the number of pounds of silver chloride you have, you may send up a smoke signal that would make an Indian proud! Why not try a small ground up sample using caustic and karo syrup. If it works, and if you grind it up fine enough in a mortar and pestle it should work, there will be much less smoke.

 

[lazersteve]

If you have time to wait the solid piece will also slowly convert to silver metal, allow it to soak in a 5-10% sulfuric acid solution with a large piece of iron.

You'll end up with a solution of iron sulfate and chlorides and a sludge of silver in the bottom.

There is a video of this reaction on my website in the silver videos section. In the video I use moist silver chloride, but I have tried it with dry silver chloride and it works, just slower. Breaking up the solids as best as you can will speed the conversion.

Steve

 

[goldsilverpro]

NH4OH. It will take about 50 gallons of 15% ammonium hydroxide to dissolve 30# of silver chloride. Nasty fumes. Really nasty to neutralize with HCl (lots of HCl needed). And then, you still will need to convert it to metal. Lots of work.

Melting. If you melt it, you will have to grind it first and blend it intimately with certain quantities of soda ash and borax. If you don't, you won't get complete conversion. To convert a particle of silver chloride to silver metal, you need a particle of soda ash right up against it. The reaction will severely eat crucibles, at about $60 a pop. There is an excellent low temp furnace method patented by Kunda, which is safer and less destructive to crucibles.
http://www.google.com/patents?id=Mj06AAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q=&f=false
http://www.google.com/patents?id=qxQwAAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q=&f=false

Karo. Fast and easy. This is how I would do it. Grind it up to face powder. A blender would probably work well. I would then weigh some out and add, for each troy ounce (31.1 grams) of AgCl, 100 ml of water, 16.5 grams of sodium hydroxide, and 11 ml of light Karo syrup. Add the powdered AgCl and stir for a long time until you have a uniform gray cement-like powder. This is best done with a motorized stirrer, preferably one that will chop up the material. You could use some form of 5 gallon paint stirrer chucked in a drill. A big blender might work great for the conversion, also. Blenders also provide heat, which would speed things up. In any case, the solution will turn a dark red/brown color.

Start small.

 

[Ignatz61]

Thanks guys,

I think I will try a small amount using several of the ways sugested. I do like the low temp furnace method. GSP do you think this will produce a lot of smoke , smell etc..? The patent say it gives off co2 and o2 ...seems pretty benign.

In the Karo method when the material turns red/brown what then? Melt? I am sorry I am just starting to learn Silver refining I know I have read about some of this on the forum but at the time it had no immediate practical purpose so It did not stick completely.

 

[goldsilverpro]

From what type of material does this AgCl come from? What process was used to produce it? Much comes from acid systems and, if any acid remains, I would expect some nasty smoke.

The efficiency of the Melting or Karo methods depends on thorough grinding of the material. I confused you with the red/brown color thing. Don't worry about that. I would stir it for at least an hour. If you do the Karo method like I said, it will work. Try a little bit.

 

[Noxx]

Harold,

Actually, AgCl is slighly soluble in concentrated HCl. I experimented this myself. I think I still have some pictures somewhere.

 

[Oz]

Chris,

If there is lead chloride in with your silver chloride and you follow this procedure would you be making a red PbO2 or yellow PbO as an indication of the lead impurity? If you did would you happen to know how the Karo would affect this or a good way to separate the silver and lead oxides at this point?

 

[Harold_V]

Harold,

Actually, AgCl is slighly soluble in concentrated HCl. I experimented this myself. I think I still have some pictures somewhere.

That makes sense, Noxx, considering the difficulty one has in extracting the last bit of silver from a gold chloride solution. Don't think it would be practical in this case, however. Sure would be a good way to wash the stuff, though, in case it was contaminated with some base metals.

Harold

 

[Harold_V]

Considering the number of pounds of silver chloride you have, you may send up a smoke signal that would make an Indian proud!

Heh! I'd forgotten that part. I experienced the same thing when I ran my waste material, although it was not just silver chloride. The furnace ran under a large hood with a 1 horse motor and blower assembly to eject all the gasses. When the operation had concluded, there was a film of white material stuck to the underside of the hood, proof positive that more than just a little was coming off the furnace. Good call, 4metals.

Harold

 

[nickvc]

personally i would dampen the chloride mix with zinc dust and add a small quantity of hydrochloric to start the reaction which should convert it back to metallic silver a bit smelly but not as bad as the melting of chloride.

 

[Juan Manuel Arcos Frank]

Let me put my two cents.I suggest two alternatives:

FIRST.- Get,for free,some spent fixer in a hospital,news paper or industrial X ray cabinet then add your dry silver chloride which will be dissolved.Add some sodium sulphide,let it settle down,pour off the liquid (it is regenerated fix),let dry the black mud (this mud is silver sulphide),mix with 1:3 of potassium nitrate (1 part of silver sulphide+3 parts of potassium nitrate) and melt it,starting with 400 C,you will see that the mixure starts to boil releasing many fumes and change to a green liquid color,rise temperature to 1000C and you will see that beautiful balls of liquid silver forms.

SECOND.- GSP has posted a patent about getting pure silver from dry silver chloride,I am not home right now so I do not have it in front of me but it says to use sodium carbonate(Na2CO3) in proportion 1:1/2,I mean,1 part of silver chloride and half part of sodium carbonate,mix well,rise temperature to 500C for half an hour,the mixure turns green due to a solid reaction between powders,mix well until all the mixure is green,then rise temperature to 1000C and you will get white and shiny silver,just like the moon.I have tried this method and it is my standard,it works lovely.

I hope it helps.

Regards

Manuel

 

[goldsilverpro]

SECOND.- GSP has posted a patent about getting pure silver from dry silver chloride,I am not home right now so I do not have it in front of me but it says to use sodium carbonate(Na2CO3) in proportion 1:1/2,I mean,1 part of silver chloride and half part of sodium carbonate,mix well,rise temperature to 500C for half an hour,the mixure turns green due to a solid reaction between powders,mix well until all the mixure is green,then rise temperature to 1000C and you will get white and shiny silver,just like the moon.I have tried this method and it is my standard,it works lovely.

I am curious as to what the green color is. It sounds like it could be either melted silver chloride or copper. If some of the AgCl melts before being converted, it could end up in the slag. Since the Na2CO3 is in great excess, the only way I can see this happening is by inadequate blending of the dry AgCl and Na2CO3 (Kunda blended it together in a blender). Also, for AgCl, he says the temp should be between 570C and 625C. Hard to control unless you have an electric furnace. Of course, since you are melting the silver at the end, it wouldn't hurt to have the temp a little on the high side. With a gas furnace, you might be able estimate the temp by color. 550C is a dark blood red and 625C is a dark cherry red

 

[Juan Manuel Arcos Frank]

GSP,my Dear Friend:

The green color of the powder means that silver chloride has reacted to form silver carbonate and sodium chloride:

2AgCl+Na2CO3-------Ag2CO3+2NaCl

at 500 C silver carbonate decomposes to silver oxide and carbon dioxide:

Ag2CO3-------Ag2O+CO2

then silver oxide is reduced(at 500C) to metallic silver:

2Ag2O--------4Ag+O2

rising to 1000C is to make silver liquid.

You are right about to control temp,it is very hard and I control it with the green color,but you have to mix pretty good the powders and make it slowly,because if you do it quickly the silver chloride is not all converted.I mean,I use the green color to ensure that all silver chloride has been converted to silver carbonate.

Soluble chlorides can be converted to their metal boiling them with a solution of sodium carbonate...Unsoluble chlorides (silver,mercury,lead and bismute) can be converted to their metals metling them with sodium carbonate.

Anyway,the patent that you have posted works pretty good.

Best regards

Your friend:

Manuel

 

[Helian]

You can very easily recover the silver from your silver chloride without producing the copious chlorine fumes you will get from a furnace. Simply put it in a plastic bucket to a depth of two or three inches at a time. Then cover it with a mixture of 20 parts distilled water to 1 part sulfuric acid, taking care to add the acid slowly with eye protection. Add enough liquid to cover the silver chloride to a depth of three or four inches. Then throw in about a pound of galvanized roofing nails. I like these because them work well and can be easily removed from the silver later with a strong magnet. Stir with a flat wooden board for about 15 to 30 minutes. You will see the silver chloride gradually turn gray (cement silver). Keep stirring until all the white silver chloride has disappeared (been reduced to silver). Do this outside, if possible, as the reaction produces hydrogen gas. When no more white chloride is visible, pour out the liquid and dispose of it safely, and then rinse the silver several more times with distilled water until all traces of acid have been removed. Then, while the silver is still covered with water, remove what's left of the nails with a magnet. Drain off the excess water, put the silver in a casserole, and warm it over a hot plate until thoroughly dry. You can sell it as a powder, or melt it into ingots. However, silver has a nasty habit of sucking up oxygen when molten, and it takes some skill to pour nice ingots.

 

[goldsilverpro]

Helian,

You can very easily recover the silver from your silver chloride without producing the copious chlorine fumes you will get from a furnace.

The copious white fumes mainly come from molten AgCl. The patents above use a temperature below the melting point of AgCl and, if I remember right, the patentee says that there are no fumes.

I see much merit in your system. You've put a lot of thought into it. I like the nails. I agree with the constant stirring. The nails also enable you to stir well and they're easy to remove. However, I would wonder if you're getting 100% conversion. When you melt, what does your slag look like? Is there a layer in between the slag and the metal?

I can see you getting 100% if the AgCl was fresh and wet. The dry AgCl poses some problems. When AgCl dries it forms crystals. In my experience, if you don't grind it to face powder (I like the blender idea), you don't get complete conversion, no matter what method you use. As the silver reduces, it forms a crust around unreacted AgCl particles, thus preventing further reaction. This unconverted AgCl is easily lost in the slag and can only be recovered by smelting. Also, in order for all of the AgCl to convert, each AgCl particle must come in intimate contact with the iron.

You can easily test for unconverted AgCl in the Ag powder. It's better to test it while it's still wet:

(1) Dip out about a gram of the Ag powder and put it into a 100ml beaker. Add about 20ml of distilled water and stir well. Allow to settle and pour off only the water. Repeat 5 or 6 times. You must rinse out all of the Cl-. Hot water may be best. Add the water from a squirt bottle and, when you add it, rinse down the inside of the beaker.

(2) Add a little nitric acid (3 or 4 ml) and some distilled water. When the Ag has completely dissolved, the presence of a white cloud or a settled white powder indicates unconverted AgCl.

 

[Platdigger]

I like Juans' "Thio" method.
As long as you can get the thio inexpensively.

Question for Juan: will sodium sulfide also precip gold from thio solutions?
I would just try it if I had some of the sulfide.

 

[oldmickster]

Hi, I have never posted anything - so don't be hard on me... Silver chloride is most often refined by using water and iron.. Zine should work fine well too. The reaction is the Fe or Zn will replace the Ag and you will have Ferric/zinc Chloride in solution and the Ag will fall out as a black paticipate. In the olden days they use to use iron pots to refine the silver chloride ore. I would first try just warming and stirring with steel wool. The extra steel wool can be removed with an HCL wash. It should be easy and not smell too bad. I have (a long time ago) use nails to drop silver collected from an analytical salt test I use to run. Best of luck..

Oldmickster