# Brown sludge in my silver solution, what is it??



## archeonist (Jun 19, 2015)

Hi guys,

I tried to refine some sterling, did it before never got any problems, and now... some kind of brown sludge appears. 

The sludge appeared when I was cementing out my silver. Maybe I did not clean the copper tubing enough. 

The tubing wasn't submerged entirely, so my theory is that it is also possible that there is some kind of copper compound contamination probably copper(I)oxide. This compound appears to have a brownisch red color. 

In the pictures I already removed my silver crystals, the rest of the solution still contains a lot of silver.

Is there anyone who has the same experiance?


----------



## Geo (Jun 19, 2015)

Take a small sample of the sludge and see if it will dissolve in hot water.


----------



## archeonist (Jun 19, 2015)

Geo said:


> Take a small sample of the sludge and see if it will dissolve in hot water.



I can't do it right now, but if it does dissolve in hot water then of course I should cool the solution with destilled ice to push out more of this contamination. 

is this your idea?


----------



## modtheworld44 (Jun 19, 2015)

archeonist said:


> Hi guys,
> 
> I tried to refine some sterling, did it before never got any problems, and now... some kind of brown sludge appears.
> 
> ...





archeonist

Did you have any sterling with clasps in the lot?
Looks like the dreaded Iron carrot cake I encountered when doing silver oxide batteries.You can check by adding a sample also to some HCL acid.Hope this is helpful and doesn't turn out to be misinformation.I could be wrong but I don't think I am.Thanks in advance.



modtheworld44


----------



## archeonist (Jun 19, 2015)

Yes I was an idiot for not checking for other metals. For sure there was also a little bit Iron here and there. 

Adding a sample to concentrated HCl? I can't do that right now, my workplace is for safety reasons not at home (have three little kids).

Monday I will try that, but what supposed to happen?
I guess there will be some white AgCl(s) formed, there are traces of AgNO3 in the sludge.
But probably there also will be FeCl4- formed a complex ion that supposed to be yellow. A good tip, I will try that.
But if there is, do you know a way to get rid of the Iron?


----------



## Lou (Jun 19, 2015)

Who cares about the iron, doesn't exactly mix with silver


----------



## Geo (Jun 19, 2015)

If you add HCl, silver chloride will precipitate. I would not want that if I could avoid it. If the sludge will dissolve in hot water, you can finish the cementation and then remove the sludge with hot water. Iron hydroxide is a red/brown gelatinous mass that is insoluble in water. If it is iron hydroxide, you may have to roast the silver and use HCl to remove the iron.


----------



## butcher (Jun 19, 2015)

Chemical reactions of Iron can have several different oxidation states, from -2 to +6, although +2 and +3 oxidation states are more common, it will also form several different iron oxide compounds, and iron oxy/hydroxides compounds.

Iron can be a complex metal when reacting it chemically with acids or bases, even the strength of the acid or base will form different reactions, temperature can also play a part in many reactions (example if a solution is boiled or not).

Dissolving iron metal in HCl will form Iron II chloride (ferrous chloride):
Fe + 2 HCl --> FeCl2 + H2(g)

But here you are not working with an iron metal any longer, the red brown sludge is more of an oxide, of iron, the red colored iron compound is likely Fe2O3 (Iron (II, III) oxide).

Fe2O3 +6HCl --> 2FeCl3 +3h20

You can also have other iron oxide or hydroxides here some of which may or may not dissolve in acid (depending on the oxidation state of the iron you are dealing with).

Iron is a metal that can get somewhat complex in its chemistry.



Iron and silver do not form an alloy when melted, (the iron oxidizes too easily) so when the silver melts the iron wil not mix with the silver metal.


----------



## solar_plasma (Jun 20, 2015)

I don't know if this is helpful in this context, but when I want to clean glass ware from those persistant iron stains, I use oxalic acid to dissolve the iron oxides.

I don't know how oxalic interacts with traces of silver salts, does anybody know if this is safe? On pure iron oxides it works fine.


----------



## Lou (Jun 20, 2015)

Silver oxalate is a bad idea.


----------



## archeonist (Jun 20, 2015)

If I want to blow myself up, it would be a great idea


----------



## solar_plasma (Jun 20, 2015)

:mrgreen: Hey, don't kick a man who already lies in the dust!  :lol: At least it has had a bad taste to me in this context in the moment I wrote it, that's why I asked, if it is safe....

Interesting how a bad idea evokes a :!: in your mind, even, when you have forgotten the reason - the link you read some months ago.


----------



## archeonist (Jun 20, 2015)

Thanks for the advice Bjorn. Silveroxalate is an explosive compound, I don't think I will try but I appreceate your input.


----------



## solar_plasma (Jun 21, 2015)

archeonist said:


> Thanks for the advice Bjorn. Silveroxalate is an explosive compound, I don't think I will try but I appreceate your input.



Of course you shouldn't :lol: yes, I remembered the posts about it, in the moment Lou mentioned it. 

There are so many hidden dangers, as soon as we just make a step beside the known ways of good procedures. Incredibly many of those dangers I first learned here, so I gained a lot not only for refining but first and foremost for my work and safety at school.


----------



## Geo (Jun 21, 2015)

One thing to really keep in mind is dissolved metals can be very unstable. The less reactive a metal is, the more explosive it becomes. Check out silver fulminate or fulminating gold.


----------



## saadat68 (Jul 19, 2017)

How you deal with this problem ?
I have same problem when refining silver oxide batteries


----------



## Lou (Jul 19, 2017)

What problem might that be?


----------



## saadat68 (Jul 20, 2017)

Brown sludge in my silver solution
I think they are iron oxide


----------



## mnap89 (Nov 29, 2017)

Hello

It seems I have ran into similar problem.
I am using sterling silver to inquart gold for refining and from time to time I drop silver from the leftover solution to get the silver back for inquartation and other things. I am cementing silver with thick copper wire/rod and never got any problem with it. Solution is filtered before proceding. Now I have got some copper looking participate along silver. Very very fine powder.. What could it be? Is it copper that somehow participated along with the silver? Tat seems impossible but...? How can I test it?
I have tried washing with hot water as someone mentioned earlier but it doesnt dissolves red powder.
I know it doesnt matter if it is copper when I am using it for inquartation. But if I would like to make some sterling out of it it would be problematic.. Or alloying gold with it.

Edit.
I have took some of this red dust and dissolved it in little bit of nitric acid. Dissolved easily giving blue/green liquid. So it is copper for sure.

I am thinking why is it there? Could it be that when you try to cement silver and there is unused nitric acid copper is dissolving too rapidly so little pariticles of it seperate from main body and they are covered with cemented silver so no silver nitrate could reach copper so it stays like this until the end?


----------



## Topher_osAUrus (Nov 29, 2017)

Try washing it with hot water a couple times to remove as much copper nitrate as possible. Then try a leach with dilute sulfuric acid (it gobbles up copper oxide), then do a wash cycle with more hot water until all the acid is washed out of the powder.

Edit
-but
The top picture looks like finely divided copper on top of the silver cement, somehow? Copper oxide comes from a few different things in the cementation process. Like having the bar sticking out of the solution, or sitting on the bottom, or having it sitting on the bottom. I think those are the primary reasons, but there is another one that deals with the free acid level in the solution being cemented.

...anyways, thats all my idears


----------



## mnap89 (Nov 30, 2017)

Ok problem solved.
I have dissolved eveything in the solution that I still have. 600ml of this solution took 43 grams of silver before it was exhausted. I have must added some "3rd nitric leech" there - that is why there was soo much unused acid.
After solution has cooled down I have put the same copper pieces and silver participated without any problems this time 

Thanks for help


----------

