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Topic: Questions about electrolyzing AgCl in ammonia  (Read 28519 times)

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Offline eprigge

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #15 on: December 01, 2012, 01:27:38 PM »
Hi.  Thanks for the reply.  If you check TWW's last post, he provides a link to this method.  It looks like the way to go if I can clean up the copper first.  The problem is that instructions are pretty vague.  How much NaOH to use - stoichiometric or an excess?  how much dextrose? sodium carbonate, borax and so on.  If you or somebody could help me with those questions then I think I'd be all set!

Regards.

Sorry, I didn't see that.  As to quantities to use for reduction, I used the info from this patent, end of page 3, beginning of page 4.  Basically, you use an excess of both NaOH and dextrose.

http://www.google.com/patents/US3658510?printsec=abstract#v=onepage&q&f=false

As to the flux quantities, I don't think they are too critical.  You want to coat your crucible with the borax/boric acid (1:1) mix and also perhaps cover a bit of the surface of the melt.  The soda ash is what reduces left over AgCl though and you would need a 1:1 molar ratio there, if you knew how much left over AgCl you had, which you won't.  So, you'd guess.  It releases CO2 when it reacts with AgCl so if you see fizzing on adding annhydrous NaCO3, there's still AgCl left.  I think.  A patent regarding that reaction:

http://www.google.com/patents/US4306902?printsec=abstract#v=onepage&q&f=false

Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #16 on: December 02, 2012, 04:37:32 PM »
Sorry, I didn't see that.  As to quantities to use for reduction, I used the info from this patent, end of page 3, beginning of page 4.  Basically, you use an excess of both NaOH and dextrose.

http://www.google.com/patents/US3658510?printsec=abstract#v=onepage&q&f=false

As to the flux quantities, I don't think they are too critical.  You want to coat your crucible with the borax/boric acid (1:1) mix and also perhaps cover a bit of the surface of the melt.  The soda ash is what reduces left over AgCl though and you would need a 1:1 molar ratio there, if you knew how much left over AgCl you had, which you won't.  So, you'd guess.  It releases CO2 when it reacts with AgCl so if you see fizzing on adding annhydrous NaCO3, there's still AgCl left.  I think.  A patent regarding that reaction:

http://www.google.com/patents/US4306902?printsec=abstract#v=onepage&q&f=false

That's interesting.  I think I get it now. 

Other questions:

* Everybody mentions Borax, but googling says borax isn't the same as soda ash.  I assume real soda ash is what I want. 

* Maybe you covered this before but what does the boric acid do?

* What's the cheapest way to get a hot flame that will work well.  Home Depot has a MAPP torch but it's $50.  Is that the best way to go?

* Do you know if the silver reduction can be done in a stainless steel container?  I'm a little nervous about doing it in a plastic bucket.

* I have a crucible to melt the silver, but nothing to pour it into.  TWW uses a block of wood carbonized.  Do you also do that?

Thanks for all the help, and it would be great for anybody else to chime in.  (Then I'll shut up with all the questions).  :)

Dan

Offline Tittywahah

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #17 on: December 02, 2012, 05:12:11 PM »
Borax is Sodium borate.  I use it as a flux and as an excellent shield against oxidation of silver and copper, it is also used to keep melting silver in a single globular shape and to stop it from splitting as you melt it, also acts to prevent silver oxide from forming during the heating process and does the same for copper.

Soda ash is Sodium Carbonate, a bleaching agent, a very strong alkali.

I use the carbonized wood, pouring it is not necessary unless you are actually wanting to pour it into a mold.  Melt and allow to cool on the wood.

Hot flame?   For small amounts of Silver under about 10 grams a normal butane pen flame from a jewellers supplier will do since the carbonized wood underneath holds and reflects back up at the bottom of the silver the heat necessary to melt the silver as you heat it from above.  Otherwise as I said before a weed burner is much hotter, I use this for larger amounts.  Maybe I should add about melting silver that it is not really fluid like say when you melt tin or lead.  You can pour the silver onto concrete really, as long as it does not run off.

Silver reduction?  I assume you mean the reaction itself?   Neither stainless steal or plastic - Never.  Glass for absolutely everything.  I hope that I have not misunderstood what you meant by 'Silver Reduction'.
« Last Edit: December 02, 2012, 05:23:48 PM by Tittywahah »

Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #18 on: December 06, 2012, 07:33:34 PM »
OK, for anybody still paying attention.  I think the lye/corn syrup method is easiest for me to get silver cement.  However, I have some confusing issues.  Any comments on my saga below are appreciated:

I’ve had these bottles of silver chloride in my basement for about 30 years, and finally got around to doing something with them.  A year or so ago, I dissolved some in ammonia and electrolyzed it.  I didn’t get very far, though.  After revisiting the subject recently on the internet, I have found out much more information than seemed available even a year or two ago.  So I’ve been playing around with techniques such as copper replacement.

So now I am serious about converting this stuff to silver ingots and being done with the issue.  The problem is that I’m having a little trouble finding a good way to take what I have now, and turn it into pure, clean silver.  Here’s what I mean:  I have about 750 grams total of dry material.  Some is pretty clean AgCl, some is dirty AgCl (meaning unknown amounts of copper contamination, and/or other metals, as well as some small bits of foreign debris caught up in the AgCl).  I have another jar of lumpy AgCl that seems to have partially converted itself over to silver over the years.  There are also some chunks of green solid in the bottle.  In addition, I have several jars of ammonia with copper in solution, with some amounts of silver and likely silver chloride in solution as well as precipitated.  I have a couple of other flasks with a small amount of clear ammonia covering a mix of AgCl and silver precipitate.  Basically, I’ve got all these different “cats and dogs” in these bottles and I want to get all the silver out of them.
My goal was to get everything into clean AgCl, and then use the lye/corn syrup method to get silver cement.  One concern is how do I get everything (silver, AgCl, copper compounds?) into solution so that I can filter out any bits of debris?  I guess any further questions would depend on that answer.

I washed one of the bottles of AgCl with some ammonia to remove any copper, and then I found that if I left copper pipe in the solution for a few days, I get a surprising amount of silver precipitate.  Is this precipitation free of copper after washing.  Should I use just distilled water to wash?

The other concern is that I was originally electrolyzing the AgCl ammonia solution in the presence of copper.  I’m thinking that if I left the electrolysis going too long, I could start plating out copper and contaminate the silver.  If so, then would I have to dissolve the silver in nitric acid, and then add HCl (or salt I suppose) to get clean AgCl and copper in solution?

That’s mostly it.  It seems a bit scatter brained but I hope my general question is understood.

Thanks.

Offline Borek

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #19 on: December 07, 2012, 05:24:45 AM »
AgCl dissolves in ammonia.
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Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #20 on: December 07, 2012, 07:41:48 AM »
AgCl dissolves in ammonia.

Have you tried to dissolve AgCl in household ammonia?  It takes a ton of ammonia.  I read that you can theoretically dissolve 1 kg of AgCl in 1 liter of concentrated (something like 25%) ammonia.  I don't know the concentration of household ammonia, but it would take gallons to dissolve what I have.

How about dissolving the silver in nitric acid, pouring it off, and then dissolving the AgCl in concentrated lye?

Offline eprigge

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #21 on: December 07, 2012, 10:42:12 AM »
I think from what you describe your best bet is going to be to sell the crude, contaminated, clumpy AgCl to someone who knows how to do the extraction.  Or pay them a fee to do the extraction and send you the purified silver.  As you are finding out, it is not easy.  IF you had pure AgCl that was fresh (finely divided) it would be quick and easy to do the lye/glucose reduction and then cast pure ingots. 

But with what you have, there will be large amounts that don't get reacted.  Clumpy AgCl doesn't react or dissolve easily at all and is a b$*%( to grind.  It will reduce with sodium carbonate in a melted state but that isn't an easy process either since you need a furnace and proper crucible and sodium carbonate tends to dissolve crucibles.  Once you've reduced it you will have some copper contamination.  Unfortunately, copper I oxide is soluble in a silver melt.

If you want pure silver you would need a two step process, reduce the crude metal, cast into an ingot and then electrolyze in silver nitrate bath to purify and melt and cast again pure.  Unless you are looking for the fun of doing the above, just sell it to a small refiner. 

Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #22 on: December 08, 2012, 06:37:18 PM »
eprigge:  Selling off doesn't sound like much fun!  Honestly, though, I'm half in it for the money, and half for the fun of it.  I may have overstated the "mess" that the AgCl is in.  I'll have to take a pic of what I have at this stage.  Does the ingot have to be .9999 pure silver to have value?  Coins are 90% silver and they have good value.  My understanding was that the ingot buyer tests the silver and pays you based on that test.  Not having ever sold an ingot, I could be way off on that.

For now I'm going to get the rest of the AgCl out of the second bottle (prolly have to bust the glass to get it out), and then see exactly what I have to work with.


Offline eprigge

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #23 on: December 08, 2012, 06:59:59 PM »
eprigge:  Selling off doesn't sound like much fun!  Honestly, though, I'm half in it for the money, and half for the fun of it. 

That problem afflicts us both.  If you want to sell a 'fine' silver ingot it better be .999+.  I can pretty much guarantee you won't get 3 9s from from crude AgCl reduction, maybe 2 9s.  In some cases impurities flux out and float off on top of a melt but copper oxide will dissolve in and contaminate a silver melt.  So it has to be electrolytically removed.  If you sell an ingot where you can't characterize the purity, you can expect a lot less money.  You can always have an a$$ay done I guess.

You could electrolyze out of an AgCl bath directly (I would use thiosulfate instead of ammonia to dissolve it) but it is *really* hard (slow) to get old, clumpy AgCl to dissolve in anything AND you need an inert anode (platinized or perhaps carbon).  And, as you pointed out, you need to know when your bath is depleted or else the copper/impurities plate out too.  AND if you don't get it all out of the bath you are wasting it...

http://www.saltlakemetals.com/Solubility_Of_Silver_Chloride.htm

If you want fun, you got it.  :-)

Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #24 on: December 08, 2012, 08:44:24 PM »
I was trying to avoid Salt Lake Minerals because their procedures for getting pure silver were depressingly complicated and expensive if you don't already have a real lab.  ::)  But thanks for the link to solubilities.

There's something I don't understand, though.  You talk about having to electrolyze silver and guess at endpoints etc etc to get anything really pure and worth selling, but what about all these guys online plating out silver from copper wire.  (as in http://www.youtube.com/watch?v=znByBb6wf7g ).  In that video, he says he plated out most of the silver from AgNO3 with copper wire, and made some AgCl in the video from what was left over.  If people are starting with sterling silver (loaded with copper) and then adding copper wire, then what are they doing with the silver they cement or precipitate out?  If they wash it and then melt it into ingots, are you saying it won't be 999 purity, or something that will bring top dollar?

Also, how do you prove you have achieved 999?  I assumed the buyer would confirm this with some kind of simple jewelers test.

Regards.

Offline Tittywahah

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #25 on: December 09, 2012, 01:53:44 AM »
I was trying to avoid Salt Lake Minerals because their procedures for getting pure silver were depressingly complicated and expensive if you don't already have a real lab.  ::)  But thanks for the link to solubilities.

There's something I don't understand, though.  You talk about having to electrolyze silver and guess at endpoints etc etc to get anything really pure and worth selling, but what about all these guys online plating out silver from copper wire.  (as in http://www.youtube.com/watch?v=znByBb6wf7g ).  In that video, he says he plated out most of the silver from AgNO3 with copper wire, and made some AgCl in the video from what was left over.  If people are starting with sterling silver (loaded with copper) and then adding copper wire, then what are they doing with the silver they cement or precipitate out?  If they wash it and then melt it into ingots, are you saying it won't be 999 purity, or something that will bring top dollar?

Also, how do you prove you have achieved 999?  I assumed the buyer would confirm this with some kind of simple jewelers test.

Regards.
I always begin with sterling silver because I do not have any pure silver.  After the displacement reaction with copper, I then filter and wash with a few rinses while still in the filter bag, I use distilled water after one treatment with 0.1 mole Nitric acid to help flush out any copper ions that might be left.  After allowing to dry it's just a simple case of heating on carbonized wood. The silver is, I believe, at the minimum 98% no less.  More steps can be achieved I believe to purity by re-dissolving in Nitric acid, getting the silver nitrate crystals then heating these back into silver.  (This seems to be the best method for obtaining max purity in a home situation/backyard chemistry so to speak)

Offline Tittywahah

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #26 on: December 09, 2012, 04:06:27 AM »
I found this in one of my articles that I have collected:  Now It may be of no use to you but I thought that I would post it anyway - I have also given a link to the original site where I found it.

""A third method of reduction of the chloride, is one which is very convenient for those who do not possess a furnace, or have the convenience of fusing ores or residues. Moisten the chloride with dilute hydrochloric acid, and immerse a plate of zinc in the moistened mass for several hours. Decomposition will gradually take place, the silver being deposited, whilst the soluble chloride of zinc is formed. After the chloride has been thus completely decomposed, the remaining zinc is withdrawn, and the precipitate is washed with dilute hydrochloric acid, until there is no longer any precipitate formed in the decanted fluid by means either of ammonia or of sulphide of ammonium. The precipitate is next well washed with warm water. It is now in a condition for being dissolved in nitric acid.""

http://albumen.conservation-us.org/library/monographs/sunbeam/chap13.html

Link: 

Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #27 on: December 09, 2012, 09:47:10 AM »
Thanks for the comments TWW.  Can I inquire as to what you do with 98+% silver ingots?

Offline Tittywahah

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #28 on: December 09, 2012, 11:13:35 AM »
Thanks for the comments TWW.  Can I inquire as to what you do with 98+% silver ingots?

I use it to make silver nitrate anhydrous for use in old photographic processes, I mean 1840's style, not black and white film.

Offline Bushka

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Re: Questions about electrolyzing AgCl in ammonia
« Reply #29 on: December 09, 2012, 11:42:42 AM »
Thanks for the comments TWW.  Can I inquire as to what you do with 98+% silver ingots?

I use it to make silver nitrate anhydrous for use in old photographic processes, I mean 1840's style, not black and white film.

That's very interesting.  I guess according to eprigge I'm going to need to get 999 purity in order for it to be sale-able.

The AgCl I'm dealing with was made by high school students a long time ago.  There are some green flakes and specs in the powder, which I attribute to some kind of copper salts.  I've washed all the silver/AgCl powder in dist. water to start, and next I thought I'd soak everything in an excess of muriatic acid to dissolve the copper salts.  I realize it won't dissolve copper, but I don't have any reason to think there is pure copper in the powder.  I have to pick up some muriatic, but I tried dissolving a little in some of that CLR I had sitting around (HCl plus sulfamic acid).  It seemed to dissolve the copper salts pretty well.

From there we'll see... but at least I can take a stab at  cleaning up, drying and pulverizing the AgCl.

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