Tumbling _cementation_

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MrCrusher

Well-known member
Joined
Mar 21, 2016
Messages
56
Location
Maryland
Hi everyone.

I have seen Lou say many times to tumble silver chloride in iron to convert into elemental silver. I have searched what I think is every way to Sunday. Now I may be overcomplicating this and looking for a post that don't exist.

Can someone confirm what I am planning to do?

I have built a nice 5 gallon bucket for tumbling in. I want to add my silver chloride 5% sulfuric acid and I acquired some nice wrought iron nails. If what I have seen and understood is correct I only need to tumble until it is converted then remove the nails?

My question then is will there be any excess iron remaining in the elemental silver after the conversion? Also after filtering the Chloride can I just put the filter papers in the tumbler as well? Will the shredded paper just burn off when melting? I will then just make shot and run through a silver cell before final melting.

It looks to me like this is the most cost effective way to process the silver. If I am wrong please enlighten me.

Thanx
Mr_Crusher
 
Last edited by a moderator:
The iron will dissolve slowly proportional to the acid and the amount of silver in the chlorides. For years I used a small scale method for converting clean chlorides from aqua regia reactions which is based on the same theory. I'll describe it here as you will be using the identical chemical process either way. And the more ways you hear the same process described, the better you understand it.

Get an old cast iron frying pan that you will from here on out consider refining equipment and never again cooking equipment! New (and unseasoned) is better because a seasoned pan which has grease in its pores will not work, you need contact with the iron and the silver, so if you are using a used pan, degrease it as completely as you can. Add your silver chloride to the pan, cover the silver chloride with a dilute sulfuric acid about a half an inch deeper than the chlorides in the pan. (Pre mix the acid about 10 water :1 sulfuric acid) and use a plastic spatula to stir the silver allowing it to contact the iron of the pan. The silver chloride will turn a dark gray when it converts and if you are doing a few ounces at a time it is easy to judge when it is done. Then pour the acid and the converted silver chloride into a filter to collect the silver, rinse it and melt it with the paper holding it.

As far as tumbling the filter papers which will break down into pulp you may be making a mess. For one the color change the silver chloride goes through when it is reduced to metallic silver is how you know when you are done. The papers will not change color and may throw you off. I would keep the papers out of the mix.

I did a lot of chemical stone removal for years on lots ranging from a few ounces to 100 ounces and accumulated the silver chloride on a lot by lot basis. The frying pan was the perfect size for what I was doing. This also eliminated fishing out any iron nails that have not dissolved.

Sooner or later the frying pan will have a very thin bottom and soon after that, no bottom. Keep an eye out for the condition of the pan so it doesn't fail while you're using it.
 
That is awesome. I have hated silver chloride forever. Done the zinc, nails, etc. Did not like doing any of them so I have just been saving it wet in a jar.
New cast iron skillet just made it on the shopping list. Great idea. Thank you for it.
 
4Metals,

Thank you for the reply. I was planning to do about 30 - 50 ounces at a time. I think that may be a little to much for a frying pan. I thought a 5 gallon bucket on a 45 deg angle would comfortably hold that amount.
I also would not have to stir it :) So that was my plan. From your description of the process it sound to me like it is a fairly quick conversion?

I did not see you say it was not an economical way to make the conversion, so I guess I am on the correct path there.

That was very good advice on the not mixing the filter papers in. Since the chloride gets sucked into the papers in the Buchner funnel. After I process a few batches and get an idea of how long it takes to convert fully. Would you agree it should be a reasonable plan to run just the saved filter papers and let them cycle another 20% of the time it normally takes for the conversion? Or will burning the paper off making the shot cause issues?

Thanx
Mr_Crusher
 
Filter papers with silver chloride can be mixed with NaOH to convert the silver chloride into silver oxide. The NaCl can be washed off and the filter with silver oxide burned and smelted with a bit of flux to collect the trash. Silver oxide breaks down to silver and oxygen from the heat.

Göran
 
Goran,

Thanx for the advice. I do not know anything about flux will just using borax be enough or should I use something else?

Thanx
Mr_Crusher
 
The frying pan was fine for silver chloride generated in stone removal lots of up to 100 ounces, actually from karat gold lots of that size as well. So the silver yield never exceeded 15 ounces. I just reduced it as it was generated and put it all in one "melt me when I'm full" bucket. I always saw silver chloride as more of a pain than it was worth. Until I melted the bucket.

You are on the right path and the only reason I mentioned the frying pan method is it is another path to the same end and I personally feel the more details a logic minded person hears, the better decisions he or she can make.

The tumbler in the 5 gallon bucket range should serve well for the quantities you are looking to process at once. And it is a quick process. The silver chloride is reduced as soon as it contacts the iron. If you make some iron nuggets that are pretty decent size, recovery will be easier and you will know if you put 5 nuggets in you need to take 5 out. As they get too small you make new ones. I'm thinking 1" rebar sliced into 1 1/2" long chunks should do well. The problem some run into is using iron so small it is difficult to get it all out because it gets lost in the gray silver fluff.

Maybe Refining Rick can tell us what he didn't like about the iron nails method. Likely it is the left over nail recovery from the silver metal. The more we all hear about a process from those who have done it, the more we all learn.

As far as losing sleep over the silver sucked into the pores of the filter paper, I would let that one pass and throw the papers in with your other used filters and any papers used for stannous testing. These papers are burned down and when you get enough you refine the powders. That kind of reminds me of a nephew of mine when he was a little kid, he obsessed so much about the one Cheerio that he lost out of his bowl that he spilled the entire bowl of Cheerios chasing it.

In case I am wrong about the filter papers, can you post a photo of the papers after you have rinsed them. Some guys get real sloppy and there is a lot of chloride remaining on a poorly scraped paper. If this is the case, Goran's method will be fine. If it is hard to see any silver and you are assuming the pores are loaded up with the white metal, try Goran's method and see if the micro bead you get is worth the effort. By the way we solved my nephew Corey's issue with Cheerios by getting him a dog, a Cheerio on the floor didn't stand a chance!
 
But my dog won't eat filter papers unless I bath them in gravy.

Just use a piece of steel pipe, 2-3" in diameter, an inch shorter than the bucket. You can stand it up, fill the bucket with silver chloride, add sulfuric, cap the bucket, then tumble. At a 45 degree angle, it will just roll in the bucket. When you are done, you can easily grab the piece of pipe & wash the silver off it, back in to the bucket...then filter. Now worries of fishing for a heavy chunk of steel that could cut your filter paper.

Although fishing for steel with a magnet makes it pretty hard to miss.
 
It's the small pieces of iron that get lost and contaminate your silver. Pipe works fine except if it's black iron it's painted and if it's galvanized, it is zinc coated. But the size is good.

The chunks of rebar bang around the bottom and give good contact too and are super reactive to a magnet in a plastic bag.

Either way is good, it's all about the iron atoms contacting the silver atoms.
 
4metals said:
Maybe Refining Rick can tell us what he didn't like about the iron nails method. Likely it is the left over nail recovery from the silver metal. The more we all hear about a process from those who have done it, the more we all learn.
Click to expand...

Yes, that was exactly it. I generally find silver chloride to just be annoying in the first place. I have tried most all accepted methods and they just seemed to be a dirty stinky hassle. I always felt that some of the "nail flakes" stayed in there.
Same for the Zinc. I tried zinc powder the first time. Don't try that. It is very messy. Then I used zinc "buttons". That worked better, but I still couldn't shake the feeling that it stayed contaminated and/or unconverted.
Really I just do not like silver chloride. I do not like waiting for it to settle or it's bulk. That is why I am loving the cast iron pan idea. I can do that batch by batch and save up metallic silver powder instead of saving the chloride, wet and hidden from light.
Do you recommend keeping cement silver wet or dry in storage? Does it even matter at that point? I wouldn't want it to oxidize in a dry powder form.
Thanks in advance.
 
Refining Rick said:
Do you recommend keeping cement silver wet or dry in storage? Does it even matter at that point? I wouldn't want it to oxidize in a dry powder form.
Click to expand...
Silver does not oxidize at room temperature. The tarnish we're familiar with on silver is a reaction with sulfur, not oxygen. You can prevent that by keeping your dry silver cement in a sealed container.

Dave
 
I have clients who dry cement silver and store it covered until they have to weigh it out and melt it with another inquart lot. Dry it well and store it in a covered container, airtight is better.

No sense melting 99+% silver just to remelt it to inquart. Every time you melt it, it costs you something.
 
I am attempting my first metal refining/recovery reaction. Yay! I am a trained chemist, but untrained in this type of chemistry and in PM recovery.

At work we occasionally make small amounts of Silver Chloride from a process that uses silver. It would be nice to recycle that back to silver metal rather then sending it out to pay someone to do it. Since I find this stuff interesting, I was going to try it in the lab. Today I set up my first reaction:

I mixed 10 g of Silver Chloride "cake" with ~3 g of Zn metal (not powder, but very fine chips) with ~75 mL of 8-10% H2SO4 and stirred it vigorously in a beaker. I believe this follows the typical sulfuric method, but using zinc chips rather than a piece of iron (i.e. skillet or pipe as mentioned above). I honestly expected these very fine Zn chips to perform the reaction faster/better than the more "crude" skillet/pipe. I completely over looked the matter of having Zn contamination because the chips will be far too fine to realistically pull out by hand. Hopefully any excess will be removable with further dilute H2SO4 washes.

The reaction has been going for only ~1 hour but there is little/no appearance change. The AgCl "cake" is rather chunky, and I didnt bother grinding/breaking it up better (it came to me wet). About how long does this reaction take? What should I expect to see as it progresses/finishes? I believe the light-gray color should change to a much darker black color?

Heading home from work shortly, will leave it stirring overnight.
 
Hi Chemtag and welcome to the forum.

As a chemist you should have an easy time to adjust to the recovery and refining of precious metals. As in all crafts, there are a lot of experience that you acquire over time, luckily here on the forum there are a number of highly skilled members that freely share their experience.

I have no personal experience on converting silver chloride this way so I can't help you with your questions on how it would look and how long time the conversion would take. I'm not even sure what mechanism lies behind silver chloride conversion with sulfuric acid.
For iron I can think of at least two different scenarios. If zinc works better, then one of them are probably wrong. :D

Since you seem to have access to a suitable lab, maybe you also have access to nitric acid. In that case I would stop the conversion after a while, wash the silver / silver chloride / zinc mixture well and then leach it with nitric acid. Filtering would separate the silver nitrate from the silver chloride (zinc would dissolve and follow the silver nitrate), then it's easy to see how much silver chloride there is left.
A piece of copper in the silver nitrate solution brings the silver back out as a fine powder.

Another alternative is using ammonia to dissolve the silver chloride from the converted silver. But this is something we usually not recommend as drying up ammonia with silver chloride can create explosive compounds. ALWAYS ACIDIFY ammonia with dissolved silver chloride to avoid dangers. The silver chloride precipitates again when the pH drops below 7.

When working with silver chloride it's always better to have it wet than dried out. Fresh is easier than stored. Fine powder better than chunky.

Let us know how it works out.

Göran
 
I fiddled with the reaction more today. I read that AgCl going to Ag metal should produce a darkening in color (i.e. white suspension to a more brown/gray/black suspension). I did observe that today. I let it stir until mid afternoon, then added a little heat (~60 C) for another hour. I then filtered and washed exhaustively with dilute H2SO4, HCl, and hot water.

However, there were a lot of large chunks of the original material still left, along with a lot of the darker powder. The chunks are unusual looking, and I suspect maybe some sort of filter-aide or other inert media that was mixed in with my "pure" AgCl sample. The material seems almost rubbery, so its hard to imagine its just clumps of AgCl powder.

I pulled out the large chunks and then took the dark powder and mixed it with HNO3. I was hoping to see a definitive reaction with nitric (I was expecting NOx fumes) but so far it hasnt done anything.

My plan is to mess with the sample a bit more, then I will probably post a new thread instead of a-hoc adding to this one. I'll make sure to have pictures and give proper details/explanation so its not painful for others to guess what I am trying to do.
 
NaOH turns silver chloride into silver oxide. After filtering off the NaCl the oxides can be leached with nitric acid. Any unreacted AgCl can be recycled back and treated again.

I suggest that you take an old silver coin or some scrap sterling jewellery to do some initial tests of the reactions of silver, that way you avoid dealing with garbage in the material. It's easier to learn when you have pure reactions without any contamination throwing you off. Hoke wrote about a number of acquaintance experiments in refining.
http://goldrefiningwiki.com/mediawiki/index.php/Hoke_acquaintance_experiments

Göran
 
Goran,

I didnt run the NaOH + Sugar reduction, so I dont believe there will be any silver hydroxide (or NaCl, for that matter).


Practicing on a silver coin is a good idea, as I could digest that with nitric acid and then crash out the silver with HCl to give "authentic" silver chloride. We might have some silver compounds on our lab shelves that I can convert to silver chloride and not bother finding and buying a silver coin.

Thanks for the tip!
 
My bad, I know you ran with zinc and sulfuric acid. I should have been more detailed in my answer.

The NaOH treatment was a suggestion to see if the remaining material was silver chloride or something else. An alternative to the zinc-sulfuric conversion.

Göran
 

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