Silver Cell - Orange in Slime

[metatp]

I just just had something happen that I have never seen before. As I was running my silver cell with silver nitrate electrolyte, SS cathode and cements silver anode, I started getting a bright orange residue in my slime. has anyone seen this before?

I am breaking down my cell, and notice that it dissolve in HCL or nitric acid. Color disappeared with stannous chloride. With HCL, the solution turned yellow. After adding stannous chloride to the sample with the HCL, yellow disappeared.

Just a little puzzling.

Thanks,
Tom

 

[Harold_V]

Sounds like you have some iron in with the silver, although I'm at a loss to explain how it might have gotten there. While gold and iron will alloy, silver and iron are reputed not to do so.

Harold

 

[metatp]

Sounds like you have some iron in with the silver, although I'm at a loss to explain how it might have gotten there. While gold and iron will alloy, silver and iron are reputed not to do so.

Harold

That's what I was thinking, but could not find a source for the iron to get into my silver. Then I remembered that I got some silver powder from someone and dumped it in with my cemented silver. I know it had a little more copper, but maybe it had other metals like iron also. I will test the powder before melting it into anodes.

Thanks,
Tom

 

[Harold_V]

This is a long shot, but when you melt your silver, are you finding a sulfide layer between the cast metal and the slag? It often resembles a layer of cast iron---gray in color and crystalline in structure. If you find you do, traces of that layer may be responsible for the results you see. I'm assuming the sulfide layer has iron within. If you've converted any silver chloride with sulfuric acid and scrap steel, that may be a source. Just thinking out loud---I haven't ever experienced what you mentioned.

Should you find you have a sulfide layer, we need to talk. It often contains silver, and can be easily recovered.

Harold

 

[metatp]

Harold,

It does not appear to be leaving this sulfide when casting, but I was not paying that must close attention. I do clean on the flux with pH down. This could leave the sulfides, but don't where the iron could come from other than the powder I received from a friend.

When I broke down the cell, some of the silver ingots for the anodes had this orange stain. It wiped off easily with a paper towel.

I will do a little more melting next week, but after using the pH down, the melt is very silver and shiny.

Regards,
Tom

 

[Harold_V]

Hmmm! A real puzzle for my simple brain.

Be certain to post what you discover. At this point I've played my small bag of tricks.

Harold

 

[nickvc]

Just a thought is it possible it's cadmium? I know spinning silver alloys use cadmium or used to.

 

[metatp]

Just a thought is it possible it's cadmium? I know spinning silver alloys use cadmium or used to.

I did have cadmium in some of the contacts I recovered silver from, but unless it was dragged down while cementing with copper, I don't know how it would get in the anodes, and stay in the slime.

I did also notice that this electrolyte was greener than others when it started to go foul. The anodes where fairly void of other PMs. There was very little slime. The anode were mostly made from silver from high temp silver epoxy. I wonder if it could be leftovers that didn't get incinerated.

It is like a golden orange color, and quite bright. If I get it again, I will take a picture.

I also just realized that I and now using silver plated copper wire that I melted to cement the silver. Maybe there are other metals in that wire.

I don't want to over think this, but here it what I am doing that maybe someone can see an issue with.

1) Dissolved silver alloy or silver composite (mainly from contacts but some sterling from candelsticks and jewelry as well) in 50/50 nitric/distilled water.

2) Filtered the solution using a few coffee filters. Water content is a little high from the rinsing of the glassware and filter.

3) Cemented with copper piping. Now using the silver plated copper wire that I melted (after melting, I used pH down, "Sodium Bisulfate" to clean of the flux). Left copper in silution and stirred every once in a while until no trace of silver when testing it HCL or sea salt.

4) Filtered and rinsed the cemented silver powder with lots of tap water (usually warm). Batch size was around 200g-300g.

5) Air dried the cemented silver powder.

6) Dumped it in a plastic container with other batches I processed.

7) Made some anodes from the bucket of silver powder by melting about 2 ozt in a clay melting dish with borax as the flux. Ususally I did not pour into a mold, but remover the silver from the dish and quenched in cool water. I would make about 7-10 at a time as I needed them.

8) Placed the anodes in the silver cell like in lasersteve's video with a stainless steal cathode.

9) Rinsed and harvested the crystals with DI water.

10) Cemented the silver out of the electrolyte and rinse water with the melted silver plated copper wire as in steps 3-6 above.

11) Rinsed the remaining undissolved anodes with DI water, and placed the cloth bag with the slime in nitric/water with enough (more than enough) nitric to dissolve any silver in the slime.

12) I rinsed the bag with DI water and dried for the next cell batch.

13) I filtered the solution and cemented the silver similar to steps 2-6 above.

14) Now when I make the anodes, they are mainly with silver powder that was recovered from the previously processed cell batches (I did notice that the cemented silver seems a little darked).

Electrolyte is made from havested crystal from previous cell batches.

Regards,
Tom

 

[nickvc]

Try testing the solution with stannous, as you say some of your material was contacts it's possible some PGMs might have got into the mix by accident or that one or two might have been alloyed or pure metals and then when melted and cemented the PGMs will come down with the silver. I'm only guessing but Harold always says if your solutions are greeny rather than blue they could possibly have values in them.

 

[metatp]

Try testing the solution with stannous, as you say some of your material was contacts it's possible some PGMs might have got into the mix by accident or that one or two might have been alloyed or pure metals and then when melted and cemented the PGMs will come down with the silver. I'm only guessing but Harold always says if your solutions are greeny rather than blue they could possibly have values in them.

I did, but did not see any signs of any PGMs. I also used DMG. Again, no sign of PMGs. I do need to check my stannous to make sure it is still good, but I think it is. I also took a small sample and added some HCL to make silver chloride and tested the resulting solution with no silver nitrate.

I will admit that I was in a rush to leave for the weekend, so I could have issues with the testing. I will follow up on the next batch which won't be for another week or so. I am still thinking there might be some small amount of Palladium, but still don't know where the orange comes from.

I am washing the cloth in AR just to make sure it is as clean as possible. I am also thinking that the orange may be soluble in hot water.

Thanks for all the advise,
Tom

 

[metatp]

Well, I think I will just give up on this one. I think I just might of received some silver powder with contaminates. When I dissolved some of the slime in nitric acid, it left a light orange stain on my glassware at the top of the solution. It had to be cleaned with diluted HCL. I think I will just dissolve all my powder again an hopefully clean this out.

Thanks all,
Tom

 

[qst42know]

Tin oxide is used in place of cadmium oxide in newer contacts. Is it possible some carried through your processing?

 

[metatp]

Tin oxide is used in place of cadmium oxide in newer contacts. Is it possible some carried through your processing?

Could be anything. The silver powder is mix with powder from a friend of mine. I should have tested his powder before mixing it with mine.

 

[metatp]

This is a long shot, but when you melt your silver, are you finding a sulfide layer between the cast metal and the slag? It often resembles a layer of cast iron---gray in color and crystalline in structure. If you find you do, traces of that layer may be responsible for the results you see. I'm assuming the sulfide layer has iron within. If you've converted any silver chloride with sulfuric acid and scrap steel, that may be a source. Just thinking out loud---I haven't ever experienced what you mentioned.

Should you find you have a sulfide layer, we need to talk. It often contains silver, and can be easily recovered.

Harold

Harold,

I think you may have found the issue. I think the iron is coming from the tongs that I sometimes use to assist in melting the silver powder. I kinda use it to mix and compress the powder to melt quicker. I then usually put the torch directly on the tongs to melt any silver that got stuck to it. I do get a gray layer as you describe, but it does appear to go away in the Sodium Bisulfate solution.

I also have not been melting these ingot to a very liquid state. Maybe I have the impurities trapped. I am now going back to the longer process I used before and see if the issue goes away.

Thanks,
Tom

 

[Harold_V]

When I melted silver for casting anodes, I insured it was totally fluid, and fluxed only with borax. The hope is that oxides will be removed, thus the borax addition. (Don't use any soda ash)

The sulfide layer most often contains silver---which can be recovered by heating the material to a molten state, then adding a length of scrap steel. Any values locked in as sulfides will be replaced by iron. In the process, the steel you add degrades, but pretty well stops doing so when all has been converted. You should notice a distinct line on the added steel where dissolution has taken place. When it stops changing, the job is done. Pour to a cone mold, where you'll find a button of metal at the bottom, a layer of sulfide on top, then the slag layer on top of the sulfide layer. It generally is easy to separate from the button, requiring only a sharp rap with a hammer. I have seen it adhere doggedly, too, however. It will always break away clean, with some effort, however. There's a distinct line between the two, they are not fused.

By the way, if you do find a sulfide layer, it will have changed physical appearance when you have removed the values. It will be finer grained, and darker in color.

Harold

 

[metatp]

When I melted silver for casting anodes, I insured it was totally fluid, and fluxed only with borax. The hope is that oxides will be removed, thus the borax addition. (Don't use any soda ash)

The sulfide layer most often contains silver---which can be recovered by heating the material to a molten state, then adding a length of scrap steel. Any values locked in as sulfides will be replaced by iron. In the process, the steel you add degrades, but pretty well stops doing so when all has been converted. You should notice a distinct line on the added steel where dissolution has taken place. When it stops changing, the job is done. Pour to a cone mold, where you'll find a button of metal at the bottom, a layer of sulfide on top, then the slag layer on top of the sulfide layer. It generally is easy to separate from the button, requiring only a sharp rap with a hammer. I have seen it adhere doggedly, too, however. It will always break away clean, with some effort, however. There's a distinct line between the two, they are not fused.

By the way, if you do find a sulfide layer, it will have changed physical appearance when you have removed the values. It will be finer grained, and darker in color.

Harold

Thanks Harold. Do you know where I can find a cone mold? I've looked before, but not intently. I also need to stop trying to cut corners. It never seems beneficial.

 

[goldsilverpro]

Here's the 8" one that I always used. They also sell a 19" one.

http://www.lmine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=LMS&Product_Code=18390&Category_Code=

 

[metatp]

Here's the 8" one that I always used. They also sell a 19" one.

http://www.lmine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=LMS&Product_Code=18390&Category_Code=

Thanks.

 

[metatp]

No more problems. I thing the biggest difference is that I am melting the silver to the point that I can pour it into a mold. I guess there was stuff captured in the ingots if not fully melted.