# Black/brown heavy powder after dissolving Ag in HNO3



## solar_plasma (Aug 29, 2013)

Yesterday I dissolved 100g of unrefined silverpowder I had made from old heavy (90g/2400cm²) plated flatware. I dissolved it it HNO3 very like I learned on the forum, di water, calculated amount of HNO3, used 4M HNO3, small increments, scrubbed the fumes. After some hours the process slowed down, but much silver was still undissolved, so I decided to add some small amounts of 3% H2O2. Next day the silver was dissolved in clear Cu(NO3)2-blue solution, but some heavy dark brown or black powders covered the bottom in a thin layer. I thought it was silver and the reaction had stopped completely, which made me assume, that all nitric was used up. So I decanted and started cementation on copper. Fairly strong reaction and fumes. Ofcourse the copper dissolved in the excess nitric. Taking the copper out resulted in redissolving the cemented silver, as expected.

Obviously the black powder is not silver. It behaves as heavy as pm precipitates. I know it's hard to guess how much it is, but from my experiences it looks very much like one or more gramms, so maybe it is half of that. When I have filtered it, I will test it ofcourse. Any suggestions so far? Is it normal to find Pd or Au in such amounts in plated flatedware from around 1900? I wouldn't have expected any Pd or Au.


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## JHS (Aug 29, 2013)

HI Solar Plasms,
maby it's my turn'
are you saying the silver redesolved in the nitric?
if it did then add one of those silver bars you burried in the back yard and leave it for a 
day or two.then when the reaction is finnished you can cement all the silver at once.
john


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## MysticColby (Aug 29, 2013)

undissolved powder is likely gold/PMG or metal oxide (most likely copper oxide)
you're adding way too much nitric if your cemented silver is dissolving after there was a piece of copper in there.
H2O2 is best to add before adding nitric. It will more efficiently convert the NOx generated from dissolving silver back into nitric, so it makes the nitric you have in there go further.


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## solar_plasma (Aug 29, 2013)

Thank you guys, this will help me with my next 400g.


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## solar_plasma (Aug 29, 2013)

When you said metal oxides, I got an idea and I just read on wikipedia, it could also be manganese IV oxide. It is heavy (5g/cm3) and will not dissolve in HNO3.


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## MysticColby (Aug 29, 2013)

was there manganese in the starting material? I haven't heard of it being used with silver.
I said metal oxides because most metals can oxidize and once oxidized, generally have low/no solubility in water and tend not to react with nitric acid.
iron oxides
aluminum oxides
copper oxides
manganese oxides
zinc oxides
tin oxides
silver oxide
etc.


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## truandjust (Jan 31, 2014)

MysticColby said:


> was there manganese in the starting material? I haven't heard of it being used with silver.
> I said metal oxides because most metals can oxidize and once oxidized, generally have low/no solubility in water and tend not to react with nitric acid.
> iron oxides
> aluminum oxides
> ...



I believe War Nickels are made of an alloy that has manganese in it. Unsure how well they would process in nitric.


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## goldsilverpro (Jan 31, 2014)

How did you process that flatware to get that 100g of Ag powder?

In my experience, it could be manganese but who cares? If it's not silver and if it doesn't interfere with the collection of silver, who cares?


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## Westerngs (Jan 31, 2014)

Well, there's always the chance it's gold. Collect it and once dry try annealing it. If it turns golden you are lucky.


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## goldsilverpro (Feb 1, 2014)

Westerngs said:


> Well, there's always the chance it's gold. Collect it and once dry try annealing it. If it turns golden you are lucky.



Maybe, if it's really, really old.


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## solar_plasma (Feb 1, 2014)

> How did you process that flatware to get that 100g of Ag powder?



That was still from my copper cell experiments (CuSO4 as the electrolyte) with very heavy plated knives, forks and spoons (90-100 g Ag per 2400cm² or per 12 forks and 12 spoons). My conclusion from those experiments has been, that it can work acceptably only if it is that heavily plated and you will not get the last gramms Ag without fouling the electrolyte.

I had lost this thread completely out of my sight. The powder didn't dissolve in AR, so I just putted the filters to other garbage, which will be incinerated and processed for any pm's later.

Thank you folks!


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## truandjust (Feb 5, 2014)

solar_plasma said:


> > How did you process that flatware to get that 100g of Ag powder?
> 
> 
> 
> ...



You mentioned that the silver content was 90-100 g/2,400 cm2 or roughly 24 pieces of silverplate. The math seems off. It's hard to believe there are 100 cm2 per item or am I missing something here?


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## solar_plasma (Feb 5, 2014)

Did you try to measure it? 12 big forks and 12 big spoons....the old ones are quite bigger than those today.


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## truandjust (Feb 6, 2014)

Wow, I hadn't but after tracing out the area on graph paper it adds up a lot quicker than you'd imagine. A serving fork or spoon is pretty darn close to the 100 cm2. So for your 90-100g range would that be considered triple plate then or a higher category?


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## solar_plasma (Feb 6, 2014)

I don't know. Sometimes, when the basemetals are exposed, it comes down in foils, which are as thick as paper or maybe even thicker. It is the standard for good plated flatware in europe. Even 120 and 150 is not uncommon.


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## truandjust (Feb 6, 2014)

Wow! I need some of that stock. If you get a chance snap a photo next time.


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## solar_plasma (Feb 6, 2014)

look on www.ebay.de and search for silber schrott 90


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## solar_plasma (Feb 6, 2014)

and here are some pics and experiences from this adventure: http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=50&t=12530&start=40


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