# Palladium from solution



## overdriv (Feb 10, 2012)

I have Palladium in solution and would like to know how to get it out of solution.

Here is how I got there:

1. Started with silver electrical parts.

2. Disolved silver in (1) nitric acid + (3-4) H2O .

3. Dropped silver out of nitric acid with table salt and H2O.

4. Tested the left over blue colored solution for PGM's and got a hit on palladium.

Now, the question is how to get the palladium out of the solution of nitric and table salt?


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## philddreamer (Feb 10, 2012)

Overdrive, you can cement the Pd with copper.

You could've cemented with copper the silver & Pd at the same time; then melted into anodes; then ran them in the silver cell. The silver would've crystalized on the cathode & the Pd would have been in the bag as sludge. The Pd sludge then processed thru HCl/Cl or AR...

Just a thought.

Phil


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## overdriv (Feb 10, 2012)

Thanks Phil

Do I need to use a Hydrogen Oxy torch to melt the Palladium after cementing, and should the palladium be refined again after cementing?

A copper pipe should work for cementing. (?)

Nick


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## philddreamer (Feb 10, 2012)

Hi Nick!


> Do I need to use a Hydrogen Oxy torch to melt the Palladium after cementing,



That's what I understand from fellow members experienced with PGM's. I've never melted any PGM's.



> and should the palladium be refined again after cementing?



If you want pure Pd, yes. You should check out Lazerstave's videos on processing Pt & Pd. Also do some searches on the topic.



> A copper pipe should work for cementing. (?)



Yes, but make sure you flatten it out with a hammer, & maybe even bend one end so no Pd deposits inside the pipe.

Take care!

Phil


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## butcher (Feb 10, 2012)

If you get a 11/2" copper pipe or bigger diameter, about 8" long you can cut it lengthwise with a big pair of tin snips, unroll it out flat (hammer and vise, or anvil), cut it to shape, long strips, punch hole if needed for putting a copper wire fro hanging, and sand of surface.

Buss bars from electrical panels, or arms from breakers (silver contact cut off), can also be used.


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## overdriv (Feb 12, 2012)

Thanks for all the responses. 

As it is I have hung the flattened copper in the solution and all that has happened is that the copper has got some black deposit on the copper and it is cemented hard to the copper and it is not like a cement like silver. If left there long enough some black kind of stuff can be seen trickling off of the bottom of the copper in the solution but we are talking about a very small amount of material. Does anyone have a chemical way of getting the pd out, either that or it is not worth while.


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## jeneje (Feb 12, 2012)

overdriv said:


> Thanks for all the responses.
> 
> As it is I have hung the flattened copper in the solution and all that has happened is that the copper has got some black deposit on the copper and it is cemented hard to the copper and it is not like a cement like silver. If left there long enough some black kind of stuff can be seen trickling off of the bottom of the copper in the solution but we are talking about a very small amount of material. Does anyone have a chemical way of getting the pd out, either that or it is not worth while.


Hello overdriv, there is a chemical way, checkout Gold-N-Scrap website by samuel-a he has two videos on the subject. This might be some help for you. I don't have the link but maybe someone else here does, and will post it for you. Good luck with your project.
Ken


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## Harold_V (Feb 13, 2012)

overdriv said:


> Thanks for all the responses.
> 
> As it is I have hung the flattened copper in the solution and all that has happened is that the copper has got some black deposit on the copper and it is cemented hard to the copper and it is not like a cement like silver. If left there long enough some black kind of stuff can be seen trickling off of the bottom of the copper in the solution but we are talking about a very small amount of material. Does anyone have a chemical way of getting the pd out, either that or it is not worth while.


What color is your solution?
How did you determine that you have palladium?

Harold


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## overdriv (Feb 13, 2012)

Hi Harold;

The solution is a very light blue, as I said it is supposedly the throw away solution from processing silver chloride out of adding table salt solution to the solution of nitric acid bearing the silver nitrate (?). 

My guess is that it may be a false reading but when I dipped my q-tip in the solution (light blue) then applied stannous chloride the q-tip turned dark blue green. 


If there is palladium I would like to recover it. I am working with 10 pounds of material.


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## patnor1011 (Feb 13, 2012)

DMG will show you Pd in a minute. Just put a drop or two inside and watch for yellow precipitate.


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## ericrm (Feb 13, 2012)

overdriv
i dont realy have experience with silver
but i often get that hard black crust on my copper when i put a copper bar in a solution that still have smb in it.

up to date i never had any pm in that crust but you still should take a knife scrape it of and test it...

each time that i have precipitate pm out of solution with copper(up to date) ,the black material is very light.
as an exemple i can put the copper bar in the beaker wait 3 sec remove it and i will see a little dark pool forming aroud my copper piece as i slowly remove it and it does that even after 12 houre (always act the same way- contrary of the crust you talk about)


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## overdriv (Feb 13, 2012)

It is so little that forms. I will test it tomorrow. I did another 6 ounces today and the solution after the silver chloride precipitation with salt water, the leftover solution was yellowish but still tested bluish green with stannous chloride for palladium.

Thanks for all of your help.

Nick


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## Harold_V (Feb 14, 2012)

overdriv said:


> Hi Harold;
> 
> The solution is a very light blue, as I said it is supposedly the throw away solution from processing silver chloride out of adding table salt solution to the solution of nitric acid bearing the silver nitrate (?).
> 
> ...


There's a very good reason why I asked. Palladium in solution forms a brown color, and it takes very little to do so. If you have a blue solution, even if it contains palladium, it won't be worth any effort to recover. The harsh reality is even traces of palladium render copper in solution a green color, and if there's enough, it gets dark green then shifts to brown green. Blue is lost almost immediately.

A test with stannous chloride isn't reliable in this instance, but a test with DMG would be. If you have any palladium present, it will reveal itself readily. In truth, I expect you don't have. 

One thing troubles me. Why are you recovering silver as chloride instead of cementing with copper? If you'd use copper, if you have palladium present, it, too, would be recovered, albeit combined with the silver. You'd recover the palladium from the slimes of the silver cell, where it would get concentrated. Just a thought. 

Harold


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## overdriv (Feb 14, 2012)

Thank you for responding, Harold.

I was waiting to hear what you had to say. You have years of wisdom in your responses. The reason I went to this process is because I plan to finish the process re- refining with a silver cell. The silver was gotten from old massive electrical parts and it was my first time processing these types of parts. I was surprised to find weird looking pieces of metal that were imbedded into or the core of the parts (silver surrounding them), these parts might be iridium the nitric does not seem to affect them. Most of them have a waffle pattern in the middle. There are various sizes and shapes. Who knows what is in these things. That is why I thought that a two different types of processes would yield a finer end product. One process may get rid of the certain impurities and the other process would get rid of others. I am probably wrong, but I have read you posts where you have said that you had to refine a batch twice. I am fairly certain there was lead used in the process of soldering, but 100% certain. Washing the silver chloride with copious amounts of hot water gets rid of the lead chloride.

I have a spectrometer. Is there some resource for the various spectrums of PGM's. That why I could identify the larger undissolved shapes/pieces. 

Thanks for your response.

Also, I would like to ask if you are familiar with the Hydrogen-Oxy torch. I have heard that it is the right torch for melting the platinum group of metals. I have been using a acetylene torch, but I get too much black carbon around the lab. 

1. Is there any other torches that can be used with the platinum group of metals as well as gold and silver? (Map-Oxy, Propane-Oxy, etc.)
2. Is there any disadvantage to using Hydrogen-Oxy torch?
3. Is there any concern for using it in a small lab (1000 sq ft).


The guys at the welding store are not much help.

Nick

Nick


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## nickvc (Feb 14, 2012)

Nick I think from the description you gave of what's not dissolved that you had silver tungsten contacts, these are very common and should yield around 40% silver, the material left should be brittle and crumble easily if it doesn't you still have silver in them so retreat them in nitric.


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## Lou (Feb 14, 2012)

Once you use oxyhydrogen you'll never want to use acetylene for anything more than blacking molds (and maybe gold melting). The only disadvantage is hydrogen is about 30% more expensive than acetylene. Also be careful to close the hydrogen fittings and check for leaks. Hydrogen is the lightest gas and easily permeates through hoses and regulator diaphragms so be sure to close the valve!


Lou


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## overdriv (Feb 14, 2012)

Thanks for the heads up on the tungsten silver contacts, I have already processed a batch from another guy and I got about 55% -60% return on the silver from that batch. So are you saying that the stuff that did not dissolve in the nitric acid is tungsten and not iridium? 

Thanks for your input.

Nick


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## overdriv (Feb 15, 2012)

Lou said:


> Hydrogen is the lightest gas and easily permeates through hoses and regulator diaphragms so be sure to close the valve!
> 
> 
> Lou



Are you saying that Hydrogen is more dangerous? I think you can get regulators that special for Hydrogen, ???? Right????

Why wouldn't you use hydrogen-oxy on gold? What would happen? 

I after shutting the handle off to stop the torch. Then I always shut the tank off first then clear the hoses then shut the regulator off and then make sure the handle's valves are closed too. That is what my jeweler buddy, Kenny Noguchi told me to do.

Good to hear from you. 


Nick


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## Harold_V (Feb 15, 2012)

overdriv said:


> Most of them have a waffle pattern in the middle. There are various sizes and shapes. Who knows what is in these things.


As you now know, they are made of sintered tungsten, and silver filled. Nick's description of how to test them for complete extraction is on the money. You'll learn that it takes a prolonged heating in nitric to extract all of the silver, but it can be extracted. Keep the vessel covered with a watch glass, so you don't lose values. I used to literally boil the solution, taking advantage of the boiling action to keep the material well stirred. Worked for me. 



> That is why I thought that a two different types of processes would yield a finer end product. One process may get rid of the certain impurities and the other process would get rid of others. I am probably wrong, but I have read you posts where you have said that you had to refine a batch twice.


The batch of silver that I had to refine twice was due to an over abundance of palladium and other values included in the anode. An impervious crust was generated on the anode, preventing silver from digesting. You most likely won't have to worry about that, and you definitely won't have to worry about that having extracted silver from the contacts you mentioned. Any of the traces of contamination that may follow the silver in cementation will most likely be removed by the borax flux you should use when you melt the recovered cement silver. Pour that silver to a cone mold, for easy separation of the slag from the silver, then re-melt the clean silver to pour your anodes. 

Messing with silver chloride is, more or less, a losing proposition, although I do encourage you to explore that process, too, for there are times when it is required. For recovering silver from contacts, though, it's pretty hard to beat the use of copper. 



> I am fairly certain there was lead used in the process of soldering, but 100% certain.


Absolutely not! Lead melts at too low of a temperature to be used for such high amperage application. It could fail under adverse conditions. I might also add that I never encountered and contacts so applied, and I processed a lot of contacts in my years. Silver contacts are typically applied with silver solder, which melts at a much higher temperature. It is also a source of some silver, so when you remove the contacts by heating, you should knock off as much of the solder as you can, too. I used to do that by heating the contact (in the mouth of my fume hood) with my torch, then giving the buss a sharp rap on the edge of a coffee can when the solder was molten. Very little solder would remain on the buss, which can then be used to cement the silver after dissolution. 



> Washing the silver chloride with copious amounts of hot water gets rid of the lead chloride.


Which should be a non-issue for those contacts. 



> I have a spectrometer. Is there some resource for the various spectrums of PGM's. That why I could identify the larger undissolved shapes/pieces.


I'm no help there. My refining was kept to a low tech level, so I'm not versed on such things. 

I do recall reading that the color bands that represent platinum can be easily confused with the color bands for iron. If you learn anything, I'd appreciate hearing from you. None of that is clear in my mind. 

No need for me to address the hydrogen torch, as I don't have any experience with one. I would suggest, however, that while an oxy/acet torch isn't the preferred method of dealing with the platinum metals, unless you expect to process them in abundance, my suggestion is to not get too caught up with a torch. I refined commercially for about 20 years and managed to accumulate only about 75 ounces of each palladium and platinum in all that time. What little I melted I did with my natural gas/oxygen torch and achieved my goals without issues. Acetylene will work, just avoid a reducing flame. By sharp contrast, it's a reducing flame you need for blackening molds, so the acetylene torch is actually quite good for both silver and gold. You're far more likely to process them than you are the platinum metals, if I'm to judge by my experience.

Harold


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## qst42know (Feb 15, 2012)

The silver braze must be alloyed with something so it melts at a lower temperature than the metals being joined. I would not be surprised to find the silver braze was alloyed with a good portion of tin.


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## overdriv (Feb 15, 2012)

Wow, Thank you for your time and your answers to my questions. As usual you hit the ball out of the park. 







> As you now know, they are made of sintered tungsten, and silver filled. Nick's description of how to test them for complete extraction is on the money.



They would not tell me where these contacts had come from or did not know. Oh, wait I remember one guy said they came from electric starter motors. 




> Messing with silver chloride is, more or less, a losing proposition, although I do encourage you to explore that process, too, for there are times when it is required. For recovering silver from contacts, though, it's pretty hard to beat the use of copper.



I am sold on inquartation and will go back to that on the next batch. But that brings out another question. If I wanted to inquart, would I just try to heat all these contacts up to the point of melting and then mix together and then dissolve in nitric? Would there not be more chance of getting more impurities in the silver?






> Absolutely not! Lead melts at too low of a temperature to be used for such high amperage application.





Thanks, did not know that. And that is why I started out on this process. 







> I have a spectrometer. Is there some resource for the various spectrums of PGM's. That way I could identify the larger undissolved shapes/pieces.





> I'm no help there. My refining was kept to a low tech level, so I'm not versed on such things.







> I do recall reading that the color bands that represent platinum can be easily confused with the color bands for iron. If you learn anything, I'd appreciate hearing from you. None of that is clear in my mind.




If I can find it, I will post it.



> Acetylene will work, just avoid a reducing flame. By sharp contrast, it's a reducing flame you need for blackening molds, so the acetylene torch is actually quite good for both silver and gold. You're far more likely to process them than you are the platinum metals, if I'm to judge my my experience.



I am not a super experienced torch man. I have a lab in a brick building with one window, so air management and keeping the place clean is important. I do have a big fan and pvc duct system and a reaction chamber that is impervious to acids. The black carbon from the acetylene is a real pain so that is my driving force to go oxy-hydrogen. As long as there is no reason not to use the torch with other metals, I think I will go that way (oxy-hydrogen). 



> Harold


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## overdriv (Feb 16, 2012)

I used the method like inquartation. Just used the solution from nitric and cemented to copper. That is working fine for now.

Thank you Harold. I am sorry you have to tell us this method so many times.


Nick


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## Harold_V (Feb 16, 2012)

Please note that the processing of melting silver contacts (not recommended) is not inquartation. Inquartation is the process of reducing gold content to 25% (quartering) in order for the base metals to be dissolved. When gold content is too high, it protects the base metals from dissolving, and when silver content is too high, it protects gold from dissolving by aqua regia. The term is not used in the discussion of processing silver. 

Because contacts have the potential to contain cadmium, you should avoid melting them. Cadmium fumes are deadly poisonous. Also, contacts hat are made of tungsten won't melt, anyway, so all you do is spin your wheels. 

Remove contacts with a torch, preferably in a fume hood, alternately, outside with a breeze from the side (not from behind---that's sure to yield problems), then dissolve them in dilute nitric. Nothing more is necessary as far as preparation is concerned. Do remember, contacts made from tungsten will require prolonged processing in order to extract all of the silver. 

Harold


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## overdriv (Feb 16, 2012)

Sorry for using the wrong term. I just recognize the process as being similar and then cementing to copper.

1.


Harold_V said:


> Cadmium fumes are deadly poisonous. Also, contacts that are made of tungsten won't melt, anyway, so all you do is spin your wheels.
> Harold



Does the Cadmium get dissolved in the nitric at all? Tungsten?

2.
On the second batch though, I started the cementing to copper and got called away. There is now too much copper debris in the washed silver. I am thinking to use a dilute sulfuric acid (1-15) or dilute hydrochloric (1-20) to clean out the copper and then rewash. Am I right or (as usual) do I still have something to learn?


3.
Aslo, philddreamer, was right. I think. I am leaving the copper in the Pd solution that we have been talking about in previous posts. After leaving the copper in the solution over night. The Pd was pretty caked on. I used the same copper to cement the silver and then will filter out in the silver cell. Again. 

Am I right or (as usual) do I still have something to learn?

Nick


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## nickvc (Feb 16, 2012)

The nitric should dissolve the cadmium but the tungsten will just sit there sulking.

The solution you have excess copper in I'd just add some more silver nitrate solution as this will consume the excess copper, avoid using wire and use sheet or bars you know why now.
Adding sulphuric will create silver sulphide so again avoid and hydrochloric won't attack copper without an oxidiser.

The cell needs to have an anode bag and to be run at the correct settings or else the Pd will co deposit with the silver, it's all here on the forum, Lazersteve has some good infrormation on his site about silver cells check it out.


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## overdriv (Feb 17, 2012)

Here is a pic of the parts that would not dissolve. Does anyone have an idea what the copper looking part that would not dissolve is made out of?


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## Harold_V (Feb 17, 2012)

overdriv said:


> Here is a pic of the parts that would not dissolve. Does anyone have an idea what the copper looking part that would not dissolve is made out of?


If I recall, it's probably an alloy that contains silver, and will dissolve with time. 

I can't address what are the results from dissolution of contacts, but one of the byproducts I found, routinely, was a light yellow substance, much like silver chloride. 

Silver that has been cemented from tungsten bearing contacts will generally have traces of tungsten included after cementation. A wash with HCl will generally yield an inky blue solution which is absent from silver recovered from other sources. Do not be too concerned about its presence, for it will be absorbed by the flux used when you melt the cement silver. 

The two waffle backed pieces are tungsten. Before you consider yourself finished with them, each of them should be broken by thumb pressure. If they break easily, and there's no distinct line inside, you can safely assume you have removed the silver. If, by chance, they do not break easily, you're likely to notice a distinct line. That represents the portion that has not had silver extracted. These are the items that benefit by a prolonged boil (I do mean boil) in a watch glass covered vessel, in dilute nitric. Only time will extract all of the silver, for the nitric has to penetrate the honeycombed tungsten to remove the silver. It's a slow process, accelerated by boiling. Include any of the pieces that didn't dissolve when you process the tungsten pieces, unless you can conclude that they do not contain silver. 

Harold


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## overdriv (Feb 18, 2012)

Thank you for your comments. I learned a lot from your posts and all of the others. Thought my nitric acid was technical grade but after spending a week working on this I went back to the carboy and read that it was only 32%. The acid did its work, and I must admit it probably gave me the opportunity to do things slow (very very slow) so that I had the opportunity to learn a lot from the procedures and do things several different ways. 

1. I tried precipitating the silver via: 

A.creating silver chloride 
1. hydrochloric acid (38%) -- good results -- thought it was expensive compared to table salt,-- volumes of water and precipitates.-- cement looking silver

2. table salt (non-iodized) -- good results -- thought is was good. -- volumes of water and precipitates.-- consistent results. -- cement looking silver


B. 100% lye (drano) and sugar -- good results -- thought it was confusing as to what to pour off and what to keep it all looks black brown, still have buckets to 
throw away 

C. cementing with copper -- good results -- great silver crystals and then lots of blackish muck as the procedure continued. Stopped the procedure and 
tested the solution found more silver and precipitated with hydrochloric acid. The blackish muck with washing
turned to kind of a cement looking color and melted to good results of silver.

All in all 4 lbs of material yielded close to 35 % silver. Another similar batch of electrical contacts that were smaller yielded 60% to weight + some gold and palladium.


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## qst42know (Feb 18, 2012)

> C. cementing with copper -- good results -- great silver crystals and then lots of blackish muck as the procedure continued. Stopped the procedure and
> tested the solution found more silver and precipitated with hydrochloric acid. The blackish muck with washing
> turned to kind of a cement looking color and melted to good results of silver.



Is there a reason you got impatient and didn't let the copper finish the job?


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## overdriv (Feb 18, 2012)

> Is there a reason you got impatient and didn't let the copper finish the job?


Lack of experience. I saw bright shiny crystals forming at first, then lots of blackish muck. I thought the blackish muck was not PGMS and just an off product/side product of the nitric acid's inability to create bright shiny crystals. 

Table salt/hydrochloric acid gives the same result all the way to the end. Not so in the cementing to copper, at least with nitric 32%.

Nick


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## overdriv (Feb 24, 2012)

Can someone chime in and comment on what is happening here. I finished recovering silver from the contacts, and found some blackish crude in the bottom of beaker. I washed it and tested with stannous. It tested positive for palladium. I started a filter and to my surprise the blackish solution turned the filter paper a dark blue, and then the solution in the bottom of the filtered beaker turned orange and some orange colored sediments formed in the bottom of the beaker. I filtered the orange colored sediments out and will show you the picture. 




I started separating the contacts to see what is causing the problem. I found this one piece that was reddish and when I scratched it, nothing would happen except when fresh water was applied to the scratch. Then it would turn black. 

Ok, I have not read anything about this. What is it? I am waiting for 10 grams of DMG. Then I can test for palladium with that. 

Have screwed up by washing this and filtering with distilled water?

Nick


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## qst42know (Feb 25, 2012)

Cobalt can be a found in contacts and can be the source a range of colors from reds to deep blues near black.

My guess is your contact alloy contains cobalt.


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## overdriv (Feb 25, 2012)

I forgot to show the color of the sediments. So here they are. The metal piece in the previous post was all this color but when scrapped and water touched the scrapped area it turn black. I have seen filtered material turn a different color before but not like this. I have read in Hoke that the (p. 168) the blackish material could be gold and the orangish material platinum, but by scrapping and adding water platinum does not become gold. Or have discovered something (LOL). Since I am usually wrong about most things, but am attempting to learn please help.

overdriv


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## overdriv (Feb 25, 2012)

I will hold the material till I get my DMG, and then test. I will NOT HEAT UP THE MATERIAL WITH A TORCH since cobalt can cause TOXIC FUMES. Thanks for your post qst42know. You just may have saved me from doing some thing stupid, like taking a torch to some to test what it will do.


I just read this from wikipedia:


"The [CoCl4]2- ion is the blue ion that forms upon addition of hydrochloric acid to aqueous solutions of hydrated cobalt chloride, which are pink."

It could be that I used some tap water by mistake and upon filtering the chlorine in the tap water caused the reaction.

But I was using nitric acid to get the silver out and then washed with (distilled) water. I will post more after testing with DMG.


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## qst42know (Feb 25, 2012)

If you used copper to cement any palladium will be with the silver. But if you used HCL or salt you produced cobalt chloride in solution.

Small changes in the chloride content in solution can alter the color.

http://chem.lapeer.org/Chem2Docs/CobaltChlorideEq.html

http://www.sciencephoto.com/media/4456/enlarge


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## overdriv (Feb 25, 2012)

Thanks,

I used only nitric acid but in making the solution I may have used some tap water with chlorine in it. That is the only way that I could have introduced chlorine in anyway. It took a week and three different new solutions to get all of the silver out of the 4 lbs of contacts. (I am using nitric acid 32%, I ordered technical grade but they sent the 32% and would not take it back after I used some. So, I have to finish it.)

I think you are right about the cobalt, after looking it up and reading more about it. The color changes and the description of it sounds right, but I can not explain why stannous chloride shows an emerald green. I will wait till I get the DMG and test with that before tossing the baby out with the bath water.


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## solar_plasma (Oct 14, 2013)

philddreamer wrote:


> The silver would've crystalized on the cathode & the Pd would have been in the bag as sludge.



Is this correct?

Why should Pd form solids in a AgNO3 electrolyte? I stumbled about this paradox when I read http://de.scribd.com/doc/46524126/Refining-Electrolysis-of-the-Secondary-Silver-Alloys, which *clearly states, that the Pd dissolves into the electrolyte AND contaminates the cathode silver.*


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## Harold_V (Oct 15, 2013)

solar_plasma said:


> Why should Pd form solids in a AgNO3 electrolyte? I stumbled about this paradox when I read http://de.scribd.com/doc/46524126/Refining-Electrolysis-of-the-Secondary-Silver-Alloys, which *clearly states, that the Pd dissolves into the electrolyte AND contaminates the cathode silver.*


My limited experience with palladium in silver indicated that when the percentage of palladium in solution, as well as that which encapsulates the anode grows large enough, there is a co-deposition of palladium. It is my opinion that it was more than simple drag-out----but I stand to be corrected if someone has evidence that my thoughts are not correct. 

When I discovered palladium was co-depositing, I simply ran the recovered crystals a second time after rinsing them well with distilled water. They part perfectly well so long as you can make good electrical contact, which I accomplished by placing an anode on top of them. No need to melt the silver. 

Harold


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## solar_plasma (Oct 15, 2013)

Thank you, Harold! Makes sense to me now. Your observations fit together with Fig. 6 in the document. I conclude, at under 2,3g/L Pd in the electrolyte the cathodic silver still reaches 99,9% purity. On the other side, to reach more than 99,99% purity the Pd content in the electrolyte has to be close to 0,0%. While looking at the other graphs, other metals do not affect the purity as much as palladium.

I think this has practical meaning on how I go on with my silver and the electrolyte I have to make. ....testing *great surprise* :lol:

_Edit': ...rereading this thread, I found that testing will be quite easy:

Harold wrote:



There's a very good reason why I asked. *Palladium in solution forms a brown color, and it takes very little to do so.* If you have a blue solution, even if it contains palladium, it won't be worth any effort to recover. The harsh reality is *even traces of palladium render copper in solution a green color*, and if there's enough, it gets dark green then shifts to brown green. Blue is lost almost immediately.

Click to expand...

_

philddreamer:


> Pd would have been in the bag as sludge



...no, it would contaminate the electrolyte


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## g_axelsson (Oct 15, 2013)

I have a feeling that palladium could report in the anode slime. It is slightly less reactive than silver and the difference in electrode potential is close to 0.1V.
To keep the palladium in the slime and not fouling the electrolyte I would suggest to run the cell on as low voltage as possible.

I wonder if it would be possible to add a bit of DMG to the electrolyte. Any Pd dissolved should precipitate inside the anode bag.

Disclaimer : I haven't tested this myself so this is just some random thoughts pulled from my disorganized brain... :roll: 

Göran


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## solar_plasma (Oct 15, 2013)

> I have a feeling that palladium could report in the anode slime. It is slightly less reactive than silver and the difference in electrode potential is close to 0.1V.
> To keep the palladium in the slime and not fouling the electrolyte I would suggest to run the cell on as low voltage as possible.



Nice piece of information!



> I wonder if it would be possible to add a bit of DMG to the electrolyte. Any Pd dissolved should precipitate inside the anode bag.
> 
> Disclaimer : I haven't tested this myself so this is just some random thoughts pulled from my disorganized brain... :roll:
> 
> Göran



But DMG has only 0,6g/L solubility in water. Would the solubility differ in the electrolyte? So, any DMG would be quickly be used up in the bag, any traces of Pd outside the bag would form solids outside the bag. Though I love that idea.


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## Lou (Oct 15, 2013)

Nioxime would be better suited, it should have more solubility and accomplish the same thing.

In any case, DMG is soluble as its sodium salt but exists in equilibrium between Na2DMG and the protonated species.


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## g_axelsson (Oct 15, 2013)

I can see a simple solution to the low solubility problem, put a bit of DMG inside the anode bag, then it will dissolve over time as the palladium reacts with the DMG in solution.

Göran


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## Harold_V (Oct 15, 2013)

g_axelsson said:


> I have a feeling that palladium could report in the anode slime. It is slightly less reactive than silver and the difference in electrode potential is close to 0.1V.
> To keep the palladium in the slime and not fouling the electrolyte I would suggest to run the cell on as low voltage as possible.


Voltage is a function of the amount of metal you hope to process, as the amperage falls as the voltage does. I chose to run my cell 'round the clock, so in order to allow getting a few hours sleep, I cut back to about 2/3 the recommended amperage for the size of my anode. I wish I could recall details now, but I can't, as I last processed silver way back in 1994. Bottom line is I did run below the recommended voltage.

Anyway, what I recall quite well is that I had problems with palladium co-depositing ONLY when there was a considerable amount present. Any at all would cause a change in color of the electrolyte (shifts to green), but it apparently didn't co-deposit until the level of concentration was so high that it didn't readily slough off the anode. I had this experience when I'd process the slimes from the cell, where some got recycled back to the cell because of incomplete extraction. The resulting silver contained so much palladium that it formed a black barrier on the anode which had to be scraped with a porcelain spatula to be removed. Under normal operating conditions, the slimes were free and easily scooped up with an acid dipper. 

Reflecting on the scraping experience, I assumed that the silver near the surface had been exhausted, leaving behind only palladium (along with gold and platinum), so palladium was then rapidly dissolved instead of silver. 



> I wonder if it would be possible to add a bit of DMG to the electrolyte. Any Pd dissolved should precipitate inside the anode bag.


Might work, but I expect not as well as you might hope. Once you started dissolving palladium, you'd most likely achieve local exhaustion of the DMG, then it would start precipitating outside the anode bag, depositing with the silver crystals. You're likely better served to simply keep the level of palladium within acceptable limits, which most likely wouldn't be much of a problem. 

Harold


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