# Recovering Silver from Silver Chloride



## hrushi

I did this Exp recently of converting AgCl to Ag

Take x Kg of dry AgCl
Take x/2 Kg NaOH, Mix Naoh and H2O Put it into AgCl
After 1 hr add x/2/3 Kg Dextrose Anhydrate(C6H12O6) 
After 6 hrs filter the whole with hot water
You get cemented silver upto 99.50 purity ready to melt

Try this!!! :idea:


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## SilverNitrate

Due to AgCl's insolubility, the silver powder formed will still contain AgCl, because the reaction has to be forced to convert the AgCl to AgOH.
You will only slightly purify the silver yield if you use an abundance of NaOH.


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## peter i

SilverNitrate said:


> Due to AgCl's insolubility, the silver powder formed will still contain AgCl, because the reaction has to be forced to convert the AgCl to AgOH.
> You will only slightly purify the silver yield if you use an abundance of NaOH.



I totally agree with this one.

A further complication is, that AgCl on drying has a tendency to become disgustingly dense, making it very hard for the reaction to reach all of it.

When performing gravimetric analysis of silver (dissolve, precipitate as chloride, wash, dry to constant weight and do the math) I've several times found a "menthos" of rock hard AgCl in the silver powder after reducing the dry pellets with zinc in dilute acid for several days.
From wet AgCl that has not been dried, the reaction will run quickly and smoothly to completion.


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## butcher

so are you saying that hrushi formula should be used on silver chloride solution and if so, how much of it should be in this formula?


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## peter i

butcher said:


> so are you saying that hrushi formula should be used on silver chloride solution and if so, how much of it should be in this formula?



Silver chloride is insoluble in water, so I guess that would be hard to do.

I have no reason to doubt that the proportions are OK, bur I've never used this method myself.
All I'm saying is, that drying silver chloride before processing may give you a whole new set of problems to deal with.
It is considered "good practice" to store your silver chloride wet, and the process it when you have collected enough to justify doing it.

If you know that you had X grams of silver to start with, you will get 1.33*X grams of silver chloride.
(MAgCl/MAg=143,3/107,9=1.33)
Then you can just scale accordingly.

Hrushi's method is a classic, but in the case of silver chloride, I prefer reduction with zinc.


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## butcher

I have not worked with silver much yet and just been collecting information, this sounds an lot like the sugar method. and even if I dont use a process it is always good for me to learn about it, it can give many clues to how things work. thanks


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## peter i

butcher said:


> I have not worked with silver much yet and just been collecting information, this sounds an lot like the sugar method. and even if I dont use a process it is always good for me to learn about it, it can give many clues to how things work. thanks



It basically is the sugar method.

Dextrose is the same as D-glucose, aka grape sugar and is the sugar found in corn syrup.


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## Sylar

I have a problem. 

I made the mistake of letting the AgCl dry before reducing it with iron in sulfuric acid. I didn't notice and placed the lot in a crucible. Out came a fraction of the expected quantity metallic silver and a lot of fused silver chloride. (I used borax flux)

This dark brown/black material will NOT dissolve in any acid I've throm at it (AR, H2SO4, HNO3) and puzzles me on what to do with it exactly ...


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## goldsilverpro

Sylar,

Silver chloride will not dissolve in acids. Silver chloride will dissolve in ammonium hydroxide, sodium or potassium cyanide, or sodium thiosulfate. Sodium thiosulfate (Na2S2O3 - photo hypo) would definitely be the safest to use of the three. I've never tried to dissolve fused AgCl in Na2S2O3 and would imagine it would go slowly. 

After dissolving in Na2S2O3, you can use zinc dust to precipitate the silver. If you use an excess of zinc (which you probably will), you will have to remove it. You can try to use a weak (10%) sulfuric solution for this purpose. Don't use HCl. Or, you can dissolve the silver plus zinc in nitric acid and and then cement the silver onto copper.

I don't know what you started with but, if you could have avoided it, you shouldn't have made silver chloride. If you started with metallic silver, you should have dissolved it in nitric and then cemented it.


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## Lou

If one has to make AgCl, never let it dry out!

If it does dry out, you're best bet it to grind it up into a powder as best as one can in a mortar and mix it with sodium carbonate with a little excess charcoal. 


Lou


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## goldsilverpro

Sylar,

Here's a statement you made on another thread:



> About as easy as precipitating AgCl



Silver chloride is very easy to make but often very difficult to deal with. After working with silver for 40 years I learned to avoid silver chloride like the plague, even if it (seemingly) took a little more effort.


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## Harold_V

Listen to what Chris said. I didn't invest as much time in refining as he did (only about 22 years for me), but I learned the same lesson early on. Avoid silver chloride unless you have no alternative. I created very little, aside from what got filtered from my gold solutions. I used it to advantage, to recover greater values in the furnace. I can't think of many other advantages, but plenty of disadvantages. 

Copper is your friend. 

Harold


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## goldsilverpro

One time I was processing about 100,000# of silver brazed stainless steel material. I set up a large volume 50/50 nitric solution and used large SS baskets and a hoist to dunk and bob the parts up and down. It was operated at room temperature. The silver content ran about 1% - 2%.

Every day, or so, I harvested silver by adding HCl and precipitating silver chloride. To prevent any Cl- from remaining in the solution, I first analysed the solution and then only added enough HCl to precipitate 90% of the silver. The added H+ somewhat rejuvenated the nitric and allowed me to continue stripping. Evaporation losses were made up by adding nitric. Since the nitric usage, when dissolving silver, is only about 50% efficient, the solution got weaker and weaker. Were I to do this again, I would experiment with using H2O2 to increase the efficiency. Also, the 10% copper in the braze used up quite a bit of the nitric.

Since everything in the system was known, I could calculate all quantities involved before starting. The initial volume of the nitric tank (probably around 500-1000 gallons - it's been too long to remember exactly - it was probably less, since I may have done it in 2 or 3 batches) was determined to give a final free nitric concentration of about 10-20%. Of course, as the [HNO3] decreased, the time cycle increased. The solution got pretty thick (from Cu concentration) at the end. Because of initial planning, everything worked perfectly.

I rinsed/decanted several times, kept the AgCl wet, and used a cut off 55 gal plastic drum to convert it to Ag. To thoroughly chop the AgCl up, there was a Lightnin' mixer in the drum. I added NaOH, in exact quantities, and let it mix for about 5 min and then added the Karo syrup. I let the mixer run for several hours. When I melted the silver, there was zero silver chloride present in the melt. In other words, I got a 100% conversion.

All in all, it took about a week, or so, to process the 100,000#. 

I mention this to show that, *in rare cases*, the production of AgCl is necessary. There was no other way to do it and be able to re-use the nitric. This was one of the few times in my life that I intentionally made AgCl.


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## Sylar

Thanks for the help.
I'll see if I can pick up some thiosulfate on my next trip to my chem supplier. Any ideas on how much I would need?

I'll also try grinding up the AgCl shot, but it appears very hard ... maybe some type of electric blender ...


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## Juan Manuel Arcos Frank

Sylar:
You can get sodium thiosulfate in a photo store,it is fixer in photography...you can get it free in a photo studio...a neewspaper or a X Ray gabinet in a hospital.

Manuel


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## Juan Manuel Arcos Frank

The much-feared silver chloride is not as bad as you say...in my special case is the raw material for silver recovery from photo processes..It had paid my bills since many years ago...it is an important intermediary in the Karo syrup refining process of silver...Of course...it has some disadvantages...never let it dry...never mix it with organic compounds because it will form a colloidal solution.

Silver chloride...do not feel bad,you are a great guy!!!!

Manuel


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## goldsilverpro

Sylar,

I think you've worked yourself in between a rock and a hard place. BTW, how much silver are we talking about?

The more I think about it, I perhaps wouldn't use Na2S2O3. I think you'll end up with some by-products that will confuse the issue - like sodium sulfide and a little silver powder. If you do try it, it will theoretically take 3.5 grams of Na2S2O3.5H2O (standard photo hypo) per gram of AgCl. In practice, it will probably take more. 

On this web page, there is a quote at the bottom:
http://www.saltlakemetals.com/Solubility_Of_Silver_Chloride.htm



> "Many texts state that Silver Chloride is soluble in Sodium Thiosulfate. It is, about like Ammonia, above, but more Silver Chloride dissolves when the solution is heated. The thing that the texts don't tell you, is that the solution is NOT clear. The solution looks like metallic water with brown mixed in with it. The solution filters well in a buchner funnel, but smells bad -- like the stinky geysers at Yellowstone. Also, as the Silver chloride is dissolving (it does not dissolve quickly) light affects it. The light reduces the Silver Chloride in the Thiosulfate solution to fine Silver powder much more aggressively than if the Silver Chloride were not in solution."



Juan,

Have you ever dissolved *Fused* silver chloride in Na2S2O3? I have not. If you have, can you give this man a detailed, step-by-step clear answer on how to do it, for a change? I don't think it's going to be that easy. I may be wrong.



Were it me, I would either (1) try the Na2S2O3, (2) dissolve it in ammonia or (3) grind it as well as possible, blend it with soda ash, and do my best to convert it in a furnace at a tightly controlled temperature.

The (2) ammonia procedure would be - dissolve in ammonia, acidify with HCl, filter the freshly made AgCl and keep it wet, and convert it to silver with Al, iron, or Karo syrup/NaOH. However, this procedure can produce explosive compounds if you do wrong things. Before doing this, I hope that Lou can chime in to keep you from being injured.

The (3) furnace method might work but, if you get it too hot, it will quickly eat the crucible. The problem is that the Na2CO3 (soda ash) must be in intimate contact with the AgCl, in order to get conversion. With powdered AgCl, this is easy. With fused AgCl, you would have problems, unless the blender worked. If the blender works, add about 1.5 times more weight of Na2CO3 than you have AgCl plus a little borax and blend them all together. Read patent numbers 4306902 and 4388109 before attempting this. 

http://www.google.com/patents?id=qxQwAAAAEBAJ&printsec=abstract&zoom=4&dq=4306902#PPA1,M1

http://www.google.com/patents?id=Mj06AAAAEBAJ&printsec=abstract&zoom=4&dq=kunda+sherritt#PPA2,M1

These patents use a temperature between 900F and 1200F. To do this, the AgCl and Na2CO3 must be in intimate contact. These temps are below the melting points of both Na2CO3 (1564F) and silver (1762F) and they won't destroy the crucible. If the stuff won't blend together, you can raise the temp up to about 1800F, with a lot of stirring, but I guarantee that the crucible will have a very short life. Been there, done that.


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## Harold_V

goldsilverpro said:


> I guarantee that the crucible will have a very short life.


I certainly agree with the short life of crucibles that are used in conjunction with soda ash. It is for that reason the tilting furnace I built used no crucible. Even with a 94% alumina lining, it enjoyed a relatively short lifespan. 

Soda ash and fluorspar should be avoided when possible. Each are very destructive of crucibles, although quite indispensable under certain circumstances. Where silver is concerned, it's best to avoid having to deal with silver chloride. 

Harold


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## Juan Manuel Arcos Frank

GSP,my Dear Friend:

I have nothing to say,you have already said everything clearly and accurately,as always.

Regards.

Manuel


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## Texas

goldsilverpro said:


> Sylar,
> 
> Silver chloride will not dissolve in acids. Silver chloride will dissolve in ammonium hydroxide, sodium or potassium cyanide, or sodium thiosulfate. Sodium thiosulfate (Na2S2O3 - photo hypo) would definitely be the safest to use of the three. I've never tried to dissolve fused AgCl in Na2S2O3 and would imagine it would go slowly.
> 
> After dissolving in Na2S2O3, you can use zinc dust to precipitate the silver. If you use an excess of zinc (which you probably will), you will have to remove it. You can try to use a weak (10%) sulfuric solution for this purpose. Don't use HCl. Or, you can dissolve the silver plus zinc in nitric acid and and then cement the silver onto copper.
> 
> I don't know what you started with but, if you could have avoided it, you shouldn't have made silver chloride. If you started with metallic silver, you should have dissolved it in nitric and then cemented it.



Hi Goldsilverpro, I read your comment, I have a 20 lbs of soda bicarbonate, clay, borax...and silver chloride, I know that because this sand turns dark at the sunligth, well, I did melt the chloride with soda and a pinch of borax, (I didnt know yours method of karo syrup), then if you say that chloride does not dissolve in nitric, what method do you recommend to me? considering the mud and other waste to stay in a filter, and get a only silver solution.
I tried with nitric: step by step
first: I sifted the sand, 2: add nitric (it bubble brown!!, and this dont have cooper, I guess) 3: filtered, and add hcl, and dont make silver chloride, then what I do?
And I put a post on how to melt silver chloride, delete  

thanks
Texas


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## solar_plasma

goldsilverpro said:


> Sylar,
> 
> Silver chloride will not dissolve in acids. Silver chloride will dissolve in ammonium hydroxide, sodium or potassium cyanide, or sodium thiosulfate. Sodium thiosulfate (Na2S2O3 - photo hypo) would definitely be the safest to use of the three. I've never tried to dissolve fused AgCl in Na2S2O3 and would imagine it would go slowly.
> 
> After dissolving in Na2S2O3, you can use zinc dust to precipitate the silver. If you use an excess of zinc (which you probably will), you will have to remove it. You can try to use a weak (10%) sulfuric solution for this purpose. Don't use HCl. Or, you can dissolve the silver plus zinc in nitric acid and and then cement the silver onto copper.
> 
> I don't know what you started with but, if you could have avoided it, you shouldn't have made silver chloride. If you started with metallic silver, you should have dissolved it in nitric and then cemented it.



I tried this once on fresh and still wet AgCl powder and it worked quite fast.


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