# retrieving fine silver metal from silver chloride solution



## jam353wih (Jan 6, 2014)

Hi guys,
I've got a question relating to the issue below.

here i got my silver chloride solution (from parting process of assay bullion) just after adding hydrochloric acid to silver nitrate solution(silver nitrate was obtained after parting process).

my question is; how can I retrieve fine silver granules from that silver chloride solution?

thanks for your time and answers.

james nanai from Lae, PNG


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## butcher (Jan 6, 2014)

jam353wih,

The question if I understand it, sounds like such an easy basic answer, I wounder if I should try to answer it, how much study have you done? if you do not know how to decant a liquid from a powder, it makes me wonder if you studied enough to mix these acids and metals.


I am also wondering why you decided to make silver chloride instead of converting the silver nitrate back to elemental silver powders.

Now you will have to convert the silver chloride back to silver metal before you can melt it.

The silver chloride will be white powders in the bottom of the vessel, you can carefully pour off the nitric/chloride solution from the white powders, or siphon them off with pipette, suction bulb, hose and syringe...

If you do not know how to treat the waste solution you can read the thread dealing with waste in the safety section.


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## 4metals (Jan 6, 2014)

James,

I agree with Butcher, if your assays were strictly gold / silver alloys with no PGM's. While the copper cementing will not yield assay grade silver it will not be contaminated with PGM's and would be a perfect candidate for small lab scale electrolytic recovery. 

Precipitating the silver with copper would also bring down the PGM's and mix them with the silver metal. If you do not purify the silver further, the PGM's will remain in the silver and cause errors in future assays. 

If you do have traces of PGM's using HCl to drop the silver as a chloride and rinsing it well followed by cementing the remaining PGM values on copper would be your best bet. If you are in a place where you can use a lot of rinse water, the caustic sugar reduction method will produce fine silver for you from the silver chlorides and that method is well documented here on the forum. 

I made my own high purity assay silver for years and always kept my PGM containing parting liquors separate from my PGM containing parting liquid. Both were processed differently but this way when my silver anodes made it to my small electrolytic cell in the lab, there was never any worry of PGM traces in my assay silver. The last thing an assayer wants to do is pay a customer for metal that wasn't in his material. 

Welcome to the forum.


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## kadriver (Jan 15, 2014)

jam353wih said:


> Hi guys,
> I've got a question relating to the issue below.
> 
> here i got my silver chloride solution (from parting process of assay bullion) just after adding hydrochloric acid to silver nitrate solution(silver nitrate was obtained after parting process).
> ...



I just did a batch of silver chloride, had 2 liters of clean silver chloride.

I washed it with lots of hot water and tested the wash water with ammonia to show any dissolved copper.

I set two 50ml beakers on a sheet of white paper then added 50ml tap water to one and 50ml wash water to the other.

Then I added about 1/2 ml 10% grocery store ammonia to the wash water in the 50ml beaker and compared the two. The ammonia will turn the wash water blue due to dissolved copper. I kept washing until this test produced zero color change in the wash water.

Once cleaned, I added tap water until there was about 500ml depth above the clean silver chloride.

Then I added about 2 1/2 pounds of sodium hydroxide, adding it slowly and stirring with home-made stir bar with trimmed model airplane propellers fixed to the bottom of a 3/8 inch OD piece of PVC about 2 feet long.

I used an electric drill to stir the silver chloride and NaOH and added the NaOH until the color turned black and no further color change took place.

I allowed this mixture to cool a bit because it will get very hot.

Then I began adding regular granulated table sugar a spoon full at a time while stirring.

Once I added the sugar too quickly and it erupted like a volcano spewing hot caustic liquid and cement silver about a foot above the reaction vessel - so add the sugar very slowly!

Once all the silver had cemented i began washing with much hot water until a strip of pH paper came up neutral from the wash water.

Once all the sugar and caustic was washed out I dried it in a Corning ware casserole dish, the melted into some nice pure silver for my silver cell.

Hope this helps.

kadriver


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## jam353wih (Feb 13, 2014)

guys,

thanks very much for your effort and time. i would like to apologise to you for not getting myself clear in the question that i have asked.

now i have been following the steps of one of the old chemist in recovering silver which he convert the silver nitrate(contain PGMs) into silver chloride. dry it to silver chloride powder and then smelt into metal form. when i used this sliver for assay bullion, i found out that my assays were incorrect.

guys, can you outline the steps clearly for me to convert silver nitrate solution back to fine silver also refine those silver chlorides metals bars to fine silver?

guys , i am just a trainned lab technician by those old chemists and your explaination would be helpful to me. 

thanks 
james


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## butcher (Feb 13, 2014)

James,

Your best bet is to do some study and research, I can answer a few questions, but for you to get a good understanding you need to do the study, the few questions I can answer will not give you the kind of education you will get on your own when you study it yourself.

Silver Ag dissolved in nitric acid HNO3 makes silver nitrate AgNO3, we can get the silver back several ways, with a displacement reaction using a metal higher in the reactivity series of metals like copper, this will give us a silver metal powder, the copper replaces the silver from solution as a silver metal powder we call silver cement (we also call this process cementing silver from solution with copper).

2AgNO3 + Cu --> Cu(NO3)2 +2Ag (S)

Whenever possible this is my choice method to get the silver from the nitrate solution, as it is metallic silver and can be easily melted after washing the contaminants, note copper will also cement palladium or platinum if it is involved in the silver nitrate, these will normally cement latter in the process after most of the silver, for me this would not be a problem as I can recover them from the silver when it is purified in the silver cell later.

Silver Ag can be recovered from nitric acid HNO3 as silver chloride AgCl, by using sodium chloride, NaCl (table salt), hydrochloric acid HCl, or other chlorides like potassium chloride...

AgNO3 + NaCl --> AgCl + NaNO3
AgNO3 + HCl --> AgCl + HNO3
AgNO3 + KCl --> AgCl + KNO3

The silver chloride is a white insoluble powder, drying it is not advised (it makes conversion to metal very difficult later, normally it should not be melted as silver chloride , silver chloride is volatile in the high temperatures needed, so silver will go up in smoke, it can be melted with sodium carbonate and charcoal but even when melted this way there will be losses (some say 3% to 7% silver loss even with this method, how much of your silver that goes up in smoke will be determined on how the melting process is done)...

silver chloride can be converted to silver metal, there are several processes this can be done with, a few common methods. Silver chloride with sodium hydroxide and karo syrup. Or silver chloride with a dilute sulfuric acid and iron metal. Or silver chloride with dilute HCl and aluminum, then there are more methods that can be used for conversion that are less common.

Normally if you have to (or for some reason choose to make silver chloride), you are best off keeping it wet and converting it back to silver metal before melting it.

Note silver as silver chloride is not the only precious metal that can vapor off in a melt with chlorides, gold is also volatile and can go up in smoke in a melt with chloride salts...


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## jam353wih (Feb 16, 2014)

Butcher, thanks very much for your assistance and advise. i will do some study first and then come back to you later especially to get a list of what equipment and reagents that will be used for refining my silver. 

thanks 
james


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## Akshay (Feb 23, 2020)

Which process is best to refining silver 
By making it silver chloride or by adding copper


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## nickvc (Feb 23, 2020)

If you want high purity silver then go for silver chloride as cementing with copper usually leaves some copper in the silver but converting chloride completely comes with its own problems.


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## Akshay (Feb 23, 2020)

But i heard that cementing silver with copper will cost more wastage than chloride


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## rickbb (Feb 24, 2020)

Refining implies that you already have metallic silver and want to "purify" it. 

If so then you want to look at a electric cell such as a thrum cell.

https://www.quora.com/What-is-a-thum-cell?share=1


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## Akshay (Feb 25, 2020)

thank you guys


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## Arthur Brown (Feb 29, 2020)

When you have silver chloride (any halide) simply complex it in sodium or ammonium thiosulphate and electrolyse the silver onto a stainless cathode against a carbon anode. Machines for the recovery of silver from photographic fixer may be available, patents and other documents will be searchable.


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## Akshay (Mar 5, 2020)

Will try that thank you


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