First attempt at silver refining

[Gsracer]

After reading for the past few months and watching numerous videos i gave it a shot today. Id say overall it was a success. I do have a few questions though.


Here was my process.


As a trial run I tried a 90 % silver coin weighing in at 12.33 grams and a demitasse sterling spoon weighing in at 10.30 grams.

I used 21 ml of nitric 70% and 21 ml of distilled water. It took roughly 15-20 minutes to dissolve this with very little heat covered.



This is what i was left with



Once it cooled i filtered it through a coffee filter and added a little distilled water to rinse the filter adding what amounted to 40 additional ml of water. You can see the distilled rinse water formed a light green cloudy division between the two layers? Could this be silver chloride? Is it possible my distilled water or coffee filter had chlorine contamination?

At this point i just stirred the liquid and went for the cementation process, this is a trial run after all.





I used a coil of copper ground wire new from a box and the silver began cementing out immediately. Took all of 5 minutes till it slowed down. I filtered this off and rinsed it 4 times with distilled water until the rinse was clear.




continued in next post

 

[Gsracer]

After i rinsed the cemented silver, i melted it into a button



the theoretical yeild was
90% coin 11.09 grams
92% spoon 9.52 grams for a total of 20.61 grams

My button came in at 17.84 grams so im at 86% recovered.

Now i know there is silver still cementing (see picture below) , im going to leave this over night. The solution is still light green and i understand it should be cobalt blue. im curious as to what could have occured when i added the distilled water in the picture in my first post and why the solution went from blue after dissoling to green in the first place.

This is where it stand as of now, this will basically sit over night.





Any tips or criticism would be appreciated as well.

Thanks

 

[Gsracer]

oh one thing to add.

In the last picture, the rest of the solution im going to leave cementing overnight, i noticed there are quite a bit of black bits cementing out with the remaining silver in solution.

Could this be PGMs?

Thanks

 

[Lino1406]

"Cloudy" that is silver chloride. Green - copper chloride. What says the distilled water is not so distilled..no PGM, it would cement fiirst

 

[Gsracer]

So basically your telling me that my Winn Dixie brand distilled water is not really distilled. That was my guess too.

Anyway of being able to tell if the water in using is actually distilled short of making it myself? Any brands I should be looking for?

Also what yield should I be expecting. I had read that <90% would be ideal.

 

[nickvc]

You can use tap water for silver refining but the trick is to add a little silver nitrate solution to your tap water stir it well and leave to settle, this will remove any chloride from the water so it’s ideal for silver recovery.

 

[Gsracer]

Well it looks like the rest dropped out over night. Better color. I’ll rinse dry and melt to a button to see what the final yield really was.

I’ll also test to see if any silver remained in solution.

What can I expect purity wise without running through a cell.

Again this was a pure learning experience for me and practice. Mostly just to see if i could do it. Lol. I have learned a lot reading on here and it has been invaluable.

 

[jmdlcar]

Thank you for posting your first attempt. I will try and remember what you did so when I do my first attempt I will try and copy what you did. It will be awhile because it to cold outside to do anything right now. I will wait tell it gets 40 F outside before I try.

 

[Martijn]

The first silver that cemented will be fairly pure and less contaminated with copper than the last bit if i understood correctly.
You can add an air bubbler to get the very last bit out like in the stockpot. Keep silver nitrate wastes out of your normal stockpot because of HCL and AgCl forming.

 

[Martijn]

And to test if all copper nitrate is rinsed out of your cemented silver: add a couple of drops of ammonia to a test tube with a bit of the rinse water. If there's any blue showing, rinse some more.
Edited: forgot the word ammonia...

 

[Gsracer]

And to test if all copper nitrate is rinsed out of your cemented silver: add a couple of drops of ammonia to a test tube with a bit of the rinse water. If there's any blue showing, rinse some more.
Edited: forgot the word ammonia...

Thank you for posting this, helped tremendously. I repeated the process this time doing that.

So since i had some succuess with the first attempt, i decided to run about 10 troy ounces through.

I began with 370.62 grams, this was a mixture of about 80 percent junk silver coins that where slick and 20 percent sterling, Plus some slag ive collected from my crucibles from when i melted sterling in the past.

I was able to process this at high heat with the beaker covered and in only required 360 ml of nitric and 370 ml of water. There was about 10 grams of material left after this completed.

I separated it into two beakers however i only took photos of 1 of them.



This time i took a copper ingot i had and used it for the cementation, worked pretty good, i think i will go with this method from here on out.





Here is my silver more or less dried, I need a buchner funnel, this is the most tedious part washing it and filtering the rinse water through a standard funnel. But the ammonia test of the rinse water posted above helped me out a lot to know when i was done.






Here is the weight albeit i believe it was a little damp.

 

[Gsracer]

i threw in the button from the first attempt to get the bar over 10 troy ounces, and placed everything into a crucible.





Into the furnace it goes, took 10 minutes.



and my completed bar with one slight defect. cant be perfect i guess.




All in all if you take out the 10 grams that didnt dissolve in the nitric the yeild is close to 88 %. Not terrible for mostly coins and a bit of sterling. I am sure there is silver in solution in my cobalt blue waste bucket. I might try to precipitate it out as silver chloride at a later date, but i need to read up more on that process.

In either case i took a sterling bar i had and processed it this evening. Its cementing as we speak so ill have a better set of numbers for that one as i know exactly what went into it.

Cheers!

 

[FrugalRefiner]

When you use copper to cement silver, avoid having any of the copper outside of the solution. Have it all submerged. Copper above the solution can oxidize, then drop off into your silver cement, lowering the purity a bit.

Dave

 

[Martijn]

Glad i could help. And nice work. Great looking bar.
Keep watching the thickness of that copper wire holding the bar up. Labglas don't like falling pieces of metal.
But why not run it through a silver cell? Do you have an xrf result of this bar?

 

[kurtak]

Gsracer

First of all I just want to say that for a beginner just starting out & learning you are doing an AWESOME job with your venture into processing silver --- clearly you have done (&/or been) doing your homework before just diving in - making a bunch of mistakes - then asking us to fix them --- so - job WELL DONE on doing your research FIRST & then setting your self up to do this right once you were ready to actually start working with the process :!:

A couple of pointers as you move forward & start working in larger batches

1) glassware is fine for doing small batch learning experiment's - but as you move up in batch size start using SS (stainless steel) SS works just fine for processing silver & you don't need to worry about breaking it like glass

2) as Dave pointed out - when cementing your silver you want the copper fully submerged in the solution - so get yourself some SS wire/rod to hang your copper from

3) to get complete cementing of the silver the silver nitrate needs to come in contact with the copper so you can't just let the copper sit in the solution - the solution needs to be stirred from time to time so that the solution further away from from the copper comes into contact with the copper (one reason for working with SS instead of glass) --- AND - as the cement builds up in the bottom of the beaker - it "traps" silver nitrate in the cemented silver & doesn't get to the copper - so - you can't just stir the solution - you have to stir the cement to bring the trapped silver nitrate up out of the cement in order for it to make contact with the copper

In other words - the stirring needs to be aggressive & done from time to time (again the reason for working out of SS instead of glass)

This set of SS pots will get you started - but when you get them you NEED to replace the rivets that hold the handles to the pots with SS screws as the handle rivets are aluminum

:arrow: www.harborfreight.com/stainless-steel-stock-pot-set-4-pc-60624.html?cid=paid_google|||60

use 1/16 inch SS TIG welding rod for hanging your copper - check with you local welding shop - they will likely give you (or sell for a few $) a couple rods --- 1/16 inch = about 14 gauge wire so good size for hanging your copper

:arrow: https://www.amazon.com/KUNWU-Stainless-Steel-Welding-ER308L/dp/B08F5F31RP/ref=asc_df_B

Here is a 21 inch SS spoon for $4.50 (good for stirring)

:arrow: https://www.restaurantsupply.com/winco-bhks-21-21-heavy-duty-solid-stainless-steel-basting-spoon?msc

Kurt

 

[Gsracer]

Glad i could help. And nice work. Great looking bar.
Keep watching the thickness of that copper wire holding the bar up. Labglas don't like falling pieces of metal.
But why not run it through a silver cell? Do you have an xrf result of this bar?

I will eventually get to a cell, but ive been learning one part at a time. From melting and casting to refining and ultimately electro-refining. My LCS is a pretty nice guy, i will take my silver over there to have it checked but the ultimate goal is running this through a cell as you stated.

Gsracer

First of all I just want to say that for a beginner just starting out & learning you are doing an AWESOME job with your venture into processing silver --- clearly you have done (&/or been) doing your homework before just diving in - making a bunch of mistakes - then asking us to fix them --- so - job WELL DONE on doing your research FIRST & then setting your self up to do this right once you were ready to actually start working with the process :!:

Thank you for the feedback, i definitly read on here for months before i joined, of course i watched sreetips on youtube which is what got me really interested. Sorry to say it was premature feedback as you will see below this is a learning experience lol and i made a few very stupid mistakes.

A couple of pointers as you move forward & start working in larger batches

1) glassware is fine for doing small batch learning experiment's - but as you move up in batch size start using SS (stainless steel) SS works just fine for processing silver & you don't need to worry about breaking it like glass

2) as Dave pointed out - when cementing your silver you want the copper fully submerged in the solution - so get yourself some SS wire/rod to hang your copper from

3) to get complete cementing of the silver the silver nitrate needs to come in contact with the copper so you can't just let the copper sit in the solution - the solution needs to be stirred from time to time so that the solution further away from from the copper comes into contact with the copper (one reason for working with SS instead of glass) --- AND - as the cement builds up in the bottom of the beaker - it "traps" silver nitrate in the cemented silver & doesn't get to the copper - so - you can't just stir the solution - you have to stir the cement to bring the trapped silver nitrate up out of the cement in order for it to make contact with the copper

In other words - the stirring needs to be aggressive & done from time to time (again the reason for working out of SS instead of glass)

This set of SS pots will get you started - but when you get them you NEED to replace the rivets that hold the handles to the pots with SS screws as the handle rivets are aluminum

:arrow: www.harborfreight.com/stainless-steel-stock-pot-set-4-pc-60624.html?cid=paid_google|||60

use 1/16 inch SS TIG welding rod for hanging your copper - check with you local welding shop - they will likely give you (or sell for a few $) a couple rods --- 1/16 inch = about 14 gauge wire so good size for hanging your copper

:arrow: https://www.amazon.com/KUNWU-Stainless-Steel-Welding-ER308L/dp/B08F5F31RP/ref=asc_df_B

Here is a 21 inch SS spoon for $4.50 (good for stirring)

:arrow: https://www.restaurantsupply.com/winco-bhks-21-21-heavy-duty-solid-stainless-steel-basting-spoon?msc

Kurt

This is great info, and perfect timing as i was just going to order some larger beakers today. Would it be safe to assume i am able to dry the cement silver in a stainless steel pan, as i am having a large issue finding suitable pyroceram locally. This will be infinitely more convenient. I tig weld so i have plenty of 308L Stainless tig rod on hand. I have been stirring frequently and vigorously. I have only accumulated about 3.5 liters of waste from what i processed so far, i ran several tests with HCL from the waste pot but did not precipitate any silver chloride. So im pretty sure i got it all out.

Well that brings me to my problem.

My first two batches went off without a hitch.

Batch 3 and 4 i made some very stupid mistakes.

Lets start with the easy one, or at least i think the easy one.

Batch 3

After i cemented all the silver, during my final rinses i noticed a brownish precipitate in the the rinse water. My sterling was 100 percent clean Sterling, with no iron of any kind. At first i thought this was iron contamination, because apparently i just dont trust the distilled water i am buying. So i continued along testing the rinse water with ammonia and not the slightest color change at all.

Precipitate in rinse water and cement






Well while i left this drying overnight, i pondered this in bed last night and when i woke up this morning i noticed it had a hit of green here and there. So i took a sample and dissolved it in a few ml of nitric and distilled water and bingo copper confirmation. I had just placed the copped bar in the beaker this time around and it came in contact with the cemented silver, i should have known this would contaminate everything. Plus with stirring i probably knocked a lot of copper.

sample of cemented powder with nitric and distilled water.




I guess i should just run this cemented silver through nitric again as this will be the easiest for me.



As for batch 4.

I had what i "thought" where 6 coin fiddleback spoons from the early 1800s, all 6 where identical but badly worn. I'm lucky had the foresight to run these on their own as i was not sure of the authenticity. I tested two of them with nitric and hcl. I grinded the bowl of the spoon with the dremel and tested with nitric and hcl and they where indeed silver. However i should have tested them all but i assumed since they where identical they would all be the same.

So i did my process, cut them into pieces, incenerated and started the reaction.

After a few minutes of digestion the reaction stalled, and stalled big time. Apparently two of the spoons where some type of plated brass i fished out those two. Well all the undigested pieces anyway. At this point there wasn't much to do so I Add a little bit more nitric and heat and continued on the process.

I was left with a forrest green solution which did indeed cement out some silver on the copper. So i now have what i assume is badly contaimated cemented silver.

What would be the ideal step here. Process this small ammount seperatly agin through nitric and see where it goes? Chuck it up as a loss due to learning? lol.






I made two clear mistakes here, the first one im thinking i let the copper sit in the cemented silver but ill wait to see what you guys have to say. The second one i made an assumption, that one will not likely happen again.

This is definitely a learning process and i am thankful for this resource.

Jerry

 

[nickvc]

Please note what I posted earlier regarding your water there is no need to use distilled water just use tap water and add silver nitrate to it and stir well, allow to any chloride to settle, decant and or filter and you are good to go.
Any silver chloride can be collected and stored wet and converted when you have sufficient to bother with.

If you did put brass into your solution it really won’t matter too much it will consume more nitric but will cause no other problems.
If your aim is to produce 999 silver then a cell is a good route but you can get that from converting silver chloride to metallic silver with a little care especially with the rinses.

 

[etack]

You also need to coat your ceramic wool.


Eric

 

[Gsracer]

Please note what I posted earlier regarding your water there is no need to use distilled water just use tap water and add silver nitrate to it and stir well, allow to any chloride to settle, decant and or filter and you are good to go.
Any silver chloride can be collected and stored wet and converted when you have sufficient to bother with.

If you did put brass into your solution it really won’t matter too much it will consume more nitric but will cause no other problems.
If your aim is to produce 999 silver then a cell is a good route but you can get that from converting silver chloride to metallic silver with a little care especially with the rinses.

Great to know, as for the tap water, here where i live. We have a very high chlorine content in our tap water since we are at sea level, right next to the ocean, with a low water table Im afraid i would end up with a ton of silver chloride as well as other contaminants. I have not looked in depth at silver chloride conversion at this point since im just starting. But i will keep it in mind. Thank you.

You also need to coat your ceramic wool.


Eric

You are absolutely right. I have some cement on order for it.


I was able to correct the issues with batch 3 and 4. I ran them through dilute nitric a second time and everything cemented cleanly.

I think im getting the hang of this now. I am testing rinse water with ammonia and hanging my copper with 308l tig wire in the middle of the solution being careful not to let it rest on the cemented silver.

I have to say these last two batches are the cleanest cement silver i have made thus far.

Pics of batch 3 and 4






Although i did notice in this picture the silver was indeed cementing on the stainless steel rod.



Here is my clean cement

 

[Martijn]

That's gorgeous to look at. Nice job.