retrieving fine silver metal from silver chloride solution

[jam353wih]

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

 

[butcher]

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.

 

[4metals]

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.

 

[kadriver]

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

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

 

[jam353wih]

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

 

[butcher]

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...

 

[jam353wih]

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

 

[Akshay]

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

 

[nickvc]

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.

 

[Akshay]

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

 

[rickbb]

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

 

[Akshay]

thank you guys

 

[Arthur Brown]

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.

 

[Akshay]

Will try that thank you

 

[Dreamer]

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

Thanks for sharing all your work K! I was searching through the site and stumbled upon this post. I ran into a problem that I know that you have dealt with before. Processing my (copper) waste bucket, I wound up with 1400 grams of material that I strained, picked out the copper particles, filtered, dried and incinerated. I cooked this stuff in dilute nitric for days (well a day and 1/2 anyways) and could not get the apparent silver to go into solution. I switched to AR to get any gold and PGM's out.

After all is said and done, I'm sitting on 1000+ grams of dried, dirty Silver chloride that appears to be impervious to Nitric acid. Since you crashed the silver market, it's not worth my time to invest in a silver cell (Lol!). Do I just melt this into shot to liberate the Chlorine and do the Sliver nitrate->Silver Chloride-> Lye and Sugar method or is there an alternative way to clean this junk up?

Thanks again for your remote mentorship!

 

[4metals]

If it was Silver cemented from nitric solutions on copper it should dissolve in nitric but if it was silver chloride it will not dissolve in nitric, ever. Fuhgettaboutit. Silver chloride is insoluble in nitric acid.

Take a small sample and see if it dissolves in ammonia. That will give us a good idea if it is silver chloride or not.

 

[Dreamer]

If it was Silver cemented from nitric solutions on copper it should dissolve in nitric but if it was silver chloride it will not dissolve in nitric, ever. Fuhgettaboutit. Silver chloride is insoluble in nitric acid.

Take a small sample and see if it dissolves in ammonia. That will give us a good idea if it is silver chloride or not.

Yeah, those halides are tough to break. I wasn't really good with keeping my nitric only waste separate at the beginning. When I dissolved the incinerated material in nitric, the stannous test was positive for Au so the chlorine became free from somewhere.

Yes, sample dissolved in ammonia but slowly. I've avoided using NH3 in my refining thus far. I'll reference Hoke and read up on it. Meantime, In my mind, Melting this into shot should free the chlorine allowing me to re-dissolve in nitric and from there, I can separate the metals. I usually just cement out the PGMs after precipitating the Au and store it for later in my journey.

Is there an easier, simpler way or one that will efficiently improve my knowledge base for my future refining endeavors?

Thanks for your help. I'm grateful to have access to guys and for this site.

 

[Yggdrasil]

Yeah, those halides are tough to break. I wasn't really good with keeping my nitric only waste separate at the beginning. When I dissolved the incinerated material in nitric, the stannous test was positive for Au so the chlorine became free from somewhere.

Yes, sample dissolved in ammonia but slowly. I've avoided using NH3 in my refining thus far. I'll reference Hoke and read up on it. Meantime, In my mind, Melting this into shot should free the chlorine allowing me to re-dissolve in nitric and from there, I can separate the metals. I usually just cement out the PGMs after precipitating the Au and store it for later in my journey.

Is there an easier, simpler way or one that will efficiently improve my knowledge base for my future refining endeavors?

Thanks for your help. I'm grateful to have access to guys and for this site.

Smelting Silver Chloride without flux is not recommended.
With flux (sodium bicarbonate if I'm not mistaken) is better but not good, heavy losses may occur.
Two methods stands out as preferable.
NaOH then Sugar and the next one is weak Sulfuric (10%) and Iron with vigorous stirring.

 

[Dreamer]

Smelting Silver Chloride without flux is not recommended.
With flux (sodium bicarbonate if I'm not mistaken) is better but not good, heavy losses may occur.
Two methods stands out as preferable.
NaOH then Sugar and the next one is weak Sulfuric (10%) and Iron with vigorous stirring.

Thanks Yggdrasil. Yes, I would normally do the NaOH sugar with clean material but this stuff is quite dirty and still has an appreciable amount of Au and PMGs locked-up. Is there a paper on the Sulfuric/Fe method you could recommend?

 

[Yggdrasil]

Thanks Yggdrasil. Yes, I would normally do the NaOH sugar with clean material but this stuff is quite dirty and still has an appreciable amount of Au and PMGs locked-up. Is there a paper on the Sulfuric/Fe method you could recommend?

No paper that I know about.
If it is moist AgCl and contaminants, I would leach it in hot AR as much as possible and then wash it thoroughly.
Then cement the values out on Copper.
Convert the AgCl to Silver, make shots/bar and run it through a Silver cell.
If it is dry AgCl I would smelt it with flux and run it through a Silver cell.
Alternatively dissolve it in Nitric leaving the Gold and some of the Pt as solids, the Silver and Pd along with some of the Pt will be dissolved and need further processing.