Unknown fixer

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R

roko.gracin

Member
Joined
Oct 27, 2012
Messages
5
Hello!

I have been trying to indentify my fixer for a long time, I have searched a lot on forums (icluding this one), I have read Hokes book and many other pdf. files related to spent fixer topic (Kodak etc.) and I know quite a bit about recovering precious metals (already have done gold recovery from e-scrap) but I still don't know what is the supstance I have..(around 100L, that's what bothers me.) Acording to most articles about recovering silver from spent fixer, indentifying should be the first step, that's why I finaly decided to ask you, the experts. So...

It is a fixer that has been used (a long time ago) for very crude x-ray imaging of ship welds. Images were made on some kind of tin and the quality was not important at all. I was told that's the reason it was reused many more times than normal fixer would be, and that the concentration of silver is much higher. My father once (a long time ago) managed to somehow recover silver via electrolysis, but the problem is that he does not longer remember how he exactly did it and I am not eaven sure if he actually did plate silver metal (he said he got black powder, which he has than had molten into a small ingot.. this to me sounds more like silver sulfide).

I have tried electrolysis many times with different currents and voltage but I have never managed to get anything except black sludge, which when dry turned brown. I don't think this is silver sulfide because it is not a dark brown and it seem to burn like sulphur does. When I add HCL to fixer, it seems to precipitate sulphur and I think it might also have some silver chloride there too. When HCL was added, it did not smell like ammonia or HCN but radher like SO2.
The fixer alone was kept in black barrels for a long time and now it is has a colour of white wine. On the bottom of a barrel is almost 2 inches thick layer of grey/white/black sand. Is it posible that this is actually silver sulphide that has dropped out of solution after a long time?
Is there any experiments I could make or information I could give you, too try to indentify it and try to recover silver from it?

Sorry for the bad spelling, greetings from Croatia, Roko Gracin.
 
If all you aretrying to accomplish is recover the silver, there is really no need to identify the type fixer you have. That would be close to impossible, as there are thousands of fixer types.

As for recovering the silver, there are several ways for you to go.

The easiest would be to add zinc powder to cement out the silver metal. The resulting silver metal could then be smelted into a bar. It would then require further refining to produce 0.999 silver.

Electrolysis is also an option. That silver would also need to be smelted and further refined. Actually, all silver recovered from fixer would need to be further refined to achieve 0.999 purity. By the way, electrolysis will not remove all the silver, there will still be some left in solution, somewhere in the hundreds of parts per million and will need to be recovered by a different method.

There are also several other precipitation methods you could try, such as sodium borohydride - I never did like to work with sodium borohydride, but some people like it.

You could also run the fixer through a steel wool silver recovery canister. It will need to be smelted to recover the silver and the total costs may be more than the worth of the silver.

I guess my recommendation would be the zinc powder.
 
I have already tried steel wooll and when I washed it and filtered, I did not get silver but instead black sludge. When It is was dry, it turned brown. I will try zinc, but I think I will get same result.. Do you have any recommendations on what to try with the mud from the bottom of canister? I got some out and it is silver colour, with some white and black chunks mixed in..
 
I have just tried melting the sand, and it burns just like sulphur, it obvioustly has a great amount of sulfur in it..
I also remember that when I did electrolysis, the black stuf I got looked the same as the stuff I got when I tried the steel wooll method. It also turned brown when it was dry and also burned like sulfur..
 
I wonder if it was a thiosulfate-based fixer, the silver (silver Halide) was dissolved in.
The black stuff turning brown is most likely your silver.

Did you wash the powders very well before trying to melt?

I would take a small portion of the powders, wash the powders very well, and try a melt with added iron to the melt, using something like a nail or a piece of rebar, bring up heat slow before melting the powders.

If you still had some steel wool undissolved it would work for the iron, but using a larger piece of iron would be easier to remove the undissolved piece of metal from the melt.

Someone else may have a better idea, or would have more experience with this.
 
When you smelt the silver, you need to add some flux chemicals to help remove the sulfur. Try soda ash and boric acid. Add some iron in the form of nails or rebar as butcher stated.
 
Today I tried to melt some pieces from the sand. First I tried to melt a bit of the grey stuf that looked just like silver powder. It burned just like sulphur with strong stench of SO2.
Then, I took a pice of black stuf which looked as it was deposeted on the walls of the tank, it looks lile piecese 1mm thick that might have just peeled of the walls. It melted very quickly and when I added some borax, it started looking like molten silver. When it cooled down it stil looked somewhat like silver, It definitely is a metal, but the problem is that it is quite lighter than sliver, it seems to melt at much lower temperature and is actualy quite soft. It also doesn't react with hot HNO3...soo..I have no idea what it might be, but it can't be silver..I think.
Today I will try electrolysis. I remember that the problem with electrolysis (last time I did it) was that one of electrodes, (I think the catode, the one on which silver should have deposeted on) was corroding quite rapidly, and it was steel.. Il try it again to to see what is the stuff I will get exactly.
Is it ok if I use a steel plate (around 10cmx10cm...cca 4x4inch) for a cathode, relatively small graphite anode (I don't think this is important) and a mobile phone charger as a generator? ( 3.7V, 355mA)And how long should it run for an experiment of 0.5L of fixer? Time doesn't play a role for me at all..if it took 1 year and if it was eficient, It would still be ok..
 
Westerngs said:
If all you aretrying to accomplish is recover the silver, there is really no need to identify the type fixer you have. That would be close to impossible, as there are thousands of fixer types.

As for recovering the silver, there are several ways for you to go.

The easiest would be to add zinc powder to cement out the silver metal. The resulting silver metal could then be smelted into a bar. It would then require further refining to produce 0.999 silver.

Electrolysis is also an option. That silver would also need to be smelted and further refined. Actually, all silver recovered from fixer would need to be further refined to achieve 0.999 purity. By the way, electrolysis will not remove all the silver, there will still be some left in solution, somewhere in the hundreds of parts per million and will need to be recovered by a different method.

There are also several other precipitation methods you could try, such as sodium borohydride - I never did like to work with sodium borohydride, but some people like it.

You could also run the fixer through a steel wool silver recovery canister. It will need to be smelted to recover the silver and the total costs may be more than the worth of the silver.

I guess my recommendation would be the zinc powder.
Click to expand...

Question: Copper would also cement out the silver (based on the electromotive series), correct? Why choose zinc over copper?
 
Zinc is a whole lot cheaper than copper, and there should not be many other metals in fixer that would contaminate the silver cement by being dropped using zinc.
 

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