Dark Dark Green Solution

[metatp]

I have another question just for my curiosity.

I have this metal melt that contain silver. I was total it has a high concentration of silver with some copper (about 8%). I also this there is a little nickel in it as well. I melted it to see how it melts compared to silver i melted in the past. It took a lot more to get it to flow. I assume there were some trace of organics, because i did get a bit of black powder when melting, but i didn't notice any smoke.

Here's my question. When I took about 130g and put it in 150ml of water and 75ml of 70% nitric, it was very reactive. Once the reaction slowed down, I add the additional 75ml of nitric. Again, it was very reaction at first and in a few minutes started slowing down. The solution is a very dark green. Most of the melt is still undissolved and it appears that silver is participating on the melt. I added a little more nitric, and the solution turned a clear blue like copper nitrate. It then turns dark green again after about a hour. What metal is making it turn a very dark green and why does it turn clear blue again once I add a little more nitric?

I have so much to learn about silver, I don't know when i will ever get to gold.

Again, thanks.

Tom

 

[Harold_V]

It's most likely the silver is making the solution green. When it turns blue, the silver in solution has probably cemented out on the copper or nickel. Refreshing with nitric re-dissolves the silver, turning the solution green once again.

I'm a bit mystified by the alloy cementing silver, however. The percentage of copper present is very closely representative of sterling, which won't cement silver. I can't help but think something else is going on. It might not hurt to check the melted bits with a magnet to see if you have included some iron inadvertently. That would cement copper, which, in turn, would cement silver.

One thing to consider. Silver and nickel do not readily alloy. I used to inquart all of my gold with silver, including white gold, which, back then, was almost 100% alloyed with nickel. It didn't pour well, usually acted "thick", for lack of a better description.

If you have traces of palladium or platinum mixed in your material, you can expect the solution to lean green as well. Each of them would cement down as a black powder, so it might not hurt to test your green solution with stannous chloride to see if it shows any values. Remember, in the presence of silver, platinum will dissolve in nitric acid alone, although not quickly.

Harold

 

[metatp]

Harold,

Thanks for your quick reply.

It's most likely the silver is making the solution green. When it turns blue, the silver in solution has probably cemented out on the copper or nickel. Refreshing with nitric re-dissolves the silver, turning the solution green once again.

That makes sense, but the opposite is happening. When I refresh with nitric, the solution turns clear blue. Maybe copper is cementing and the silver cementing on the copper? Refreshing with nitric may be dissolving the cemented copper?

I'm a bit mystified by the alloy cementing silver, however. The percentage of copper present is very closely representative of sterling, which won't cement silver.

I am guessing that there is more copper than I was told, but the metal is not copperish in color.

It might not hurt to check the melted bits with a magnet to see if you have included some iron inadvertently. That would cement copper, which, in turn, would cement silver.

I did test the alloy with a magnet. It is a strong neodymium magnet, and it did not appear magnetic. I do not know how much iron needs to be present to detect.

If you have traces of palladium or platinum mixed in your material, you can expect the solution to lean green as well. Each of them would cement down as a black powder, so it might not hurt to test your green solution with stannous chloride to see if it shows any values. Remember, in the presence of silver, platinum will dissolve in nitric acid alone, although not quickly.

I think this comes from melted jewelry. I was wondering about platinum or white gold, but I did not see any black precipitant. It is dissolving very slowly. I will test. I did not know what nickel would do and thought I could detect that with the magnet as well.

I took the piece out of the nitric. Almost half of it has dissolved. It definitely looks like the copper is cemented on the piece, but it scrapes off easily. There does not appear to be any reaction left in the solution, and a little silver cement is on the bottom.

Tom

 

[metatp]

What about brass? After taking the piece out of the nitric and cleaning it up, the color of the metal appears to be a little brass in color.

 

[Harold_V]

What about brass? After taking the piece out of the nitric and cleaning it up, the color of the metal appears to be a little brass in color.

Hmmm! That's something to consider. You may have enough zinc present to cement copper. If that be the case, I expect it would happen only until the exposed zinc was consumed cementing copper, then the action would cease.

In my years of refining, I encountered flatware from one of the Scandinavian countries. It was marked 720, so it contained 28% copper. It looked very much like sterling, although with a hint of yellow, more so than sterling. Point is, you can have a considerable amount of copper present and still have a relatively white alloy. Much the same as 18K white gold. 75% gold, yet it's white.

I agree, my comment on the solution turning blue when nitric was added was exactly opposite to what I said----but if there's considerable zinc in the mix, perhaps that would explain the color change. Otherwise I'm lost in this thing.

If I had doubts about anything, I'd usually test with straight nitric. If I got a blue or green reaction, the next test would be with a trace of HCl, to see if I got a white precipitant. I would also test the piece(s) with Schwerters. In this case, it's obvious you know you have silver, the question is what are the other constituents.

If you'd like to test for nickel, put a drop of the solution in a spot plate, then add a drop of ammonium hydroxide. That should develop a strong blue color. Next, add a drop of DMG to the same sample. If you have nickel present, the color will shift to a beautiful, very bold, pink. I don't expect that nickel is part of what's happening, but it might be nice to know if it's present.

Sorry I'm not more help. Some times I had to be satisfied that I was recovering what ever values were present without knowing what the base metals were. Doesn't really matter if you achieve your goal. 8)

Harold

 

[metatp]

Well, it appears that it was another case of fraud where someone was selling 10 OZ bars where the center core is melted brass. About half of the bar is sterling silver. Doesn't seem like a profitable counterfeiting, but what people will do to for a few bucks. It was a great learning experience for me.

 

[metatp]

Well now I really perplexed. I cemented what I thought was silver with a piece of copper. After rinsing several time with hot distilled water, I noticed that the filter paper had some tannish discoloration. I also noticed that the cement was not as gray as usual. It had a pale green tint, even though the filter solution was clear. I decided to add a little 31% HCL to the filtered cement, and it immediately turned a dark brown/black. A black solution was created and passed right through the filter.

I will test the solution and what is left of the cement once I get the chemical in, but does anyone know what i might have?

Again, here is the background.

I had what looked like melted silver. I put it into 50/50 70% nitric/water. The reaction was quick for a while and then it stopped. the solution was a dark opaque green. Metal was not magnetic. What apeared to be silver started to precipitated. I added more nitric. The solution turned clear blue like copper nitrate and then there was a strong reaction again and the silution turned dark green again. I removed what was left of the metal piece. It appears to have copper cementing on it and silver cementing over that. I cleaned up the metal, and it now has a brass tone to it.

I filtered the solution, but everything appeared to go into solution and passed through the filter. I added a piece of copper and slowly what appeared to be a small amount of silver was cementing. After a few hours, I tested the solution with salt, and there apeeared to still be silver in the solution. I let the copper sit over night and most of the next day. I then tested today with salt, and there was no more cloudyiness forming. I filter what i thought was silver until i added the HCL.

There is much less mud left, but now it looked more like the gray I remember.

Any thought? Anyone? while I wait.

Thanks,
Tom

 

[Harold_V]

None from me. I don't recall ever having a similar experience. I must say, it's weird.

Could be GSP will have something to offer. He processed one hell of a lot more silver than I did, and has done it for more years. Could be he's seen something similar.

The black solution is very curious. I know, from washing silver recovered from tungsten contacts, that the solution will turn a very dark blue when HCl is added, but I've never witnessed a black result.

Harold

 

[Anonymous]

In the beginning of my refining career last year this was one of my first of many screw ups, I think you may have added some pewter to your silver.

 

[metatp]

In the beginning of my refining career last year this was one of my first of many screw ups, I think you may have added some pewter to your silver.

I am sure this is a mixture of a bunch of junk. I even saw on a similar piece I have there was some Nickel Silver etch on a semimelted slab. There may be some of this junk in the sample I digested as well. There was probably some brass as well. The chunk of melt appears to have a higher than silver melting point based on how difficult it was to melt. I don't know how much pewter would need to be in the mix for the results I've seen.

My biggest question is what was cemented on the copper. It appeared to be a small amount of silver, but now I am not sure. I have save all the solutions thus far, and the HCL is still black with a trace of very fine silverish white substance on the bottom.

I dried the small amount of cemment that appears to be darker than the usual silver. Kinda has a slight purplish tint.

One lesson I learned is that maybe I should test my melts before waisting precious nitric with base metals. Personally, I think most if not all of this is base metals all melted together.

 

[Anonymous]

At this point I would suggest that you drop everything in solution with iron and save the goop for a later date when you have learned how to deal with it.

Some of the professionals here on the forum made their mad money from that slop bucket.

Best Regards
Gill

 

[metatp]

I decided to melt the the 2g of powder I recovered after rinsing in HCL. Even though I rinsed in water, I am sure there are still chrorides in there.

Right when I started melting, I got this beautiful blue (not greenish) flames. It lasted for a while before I created a 2g silver colored button I will tested it later.

Anybody know what would create this blue flame?

Tom

 

[butcher]

burning copper is blue and if acidic you probably burned off it and other base metals even gold can come off in vapors of chloride gases.
I would heat slowly to drive off acid salts before hitting it hard with a torch.

now you can refine that button, but this time prepare don't just jump into it, gather your plan, study, we want to see that pure gold button go into your pocket not up in smoke.
:lol:

 

[metatp]

The blue flame looks differnet from the copper blue flame I got with copper chloride. It was a bright blue. I am not expecting gold, and just trying to learn by a little testing. Since I done know exactly what this mixture of metal is, I should be more careful just in case there are PMs

 

[butcher]

burning metal powder's can be dangerous, I would worry about burning metals which I wasn't sure what they were, a man sucking in air like that may find he can no longer breath.
please take some time studying (it's fun), collect and save up things to process, do simple expieriments to learn testing and how these metals react to the chemistry, gain some understanding and arm yourself with the knowledge to do this,
that way you will gain gold in yer poke, not up in smoke. good luck.

 

[metatp]

Butcher you are right and i know better. My problem is that I took the word of someone that I got the metal from. As Harold says, I should not be going in blind. It is fun to see different reactions, but I need to make sure I stay safe and also not lossing PM.

I did some testing of the metal the inner core appears to be mainly brass with a little nickel on top. The 2g button I made is silver, so that is what was cemented by the copper. 2 whole grams of silver from a 134g slab. Not bad. OK it is bad.

Regards and thanks all.

 

[butcher]

treating gold/silver powders in used acid peroxide (unconventional recovery process I have been using), when I treat silver powders from old contact points in a chloride solution, if my copper content is high, and solution very concentrated the silver chloride will stay in mostly solution, and I get a green precipitant even in hot solution, I believe besides what silver chloride that may not be colloided, it is a combination of metals, that are not soluble as hot concentrated chlorides, besides salts and salts of metals, gold, possible platinum palladium,maybe some silver, copper chloride, maybe even tungsten cobalt, not sure of exact mix,some of this acid complex has had many metals in them, but I save these for a later refining as they are sure to be money in the bank someday.