Silver Tungsten 50:50and some are 50:50 silver/Molybdenum

[Anonymous]

I have access to Some electrical contacts are approximately 50:50 Ag-W, and some are 50:50 Ag-Mo. They were manufactured by melting pure silver onto powdered W (or Mo), resulting in a 50:50 composition.

About 4 pounds

Can the silver be recovered from the Tungsten and the Molybdenum?
What process can be used?

I have processed electrical contacts before and I know that when I try to melt the contacts the Tungsten will not melt in my furnace. They just stick in the slag.
I am not sure the composition of the ones that I messed with before. I just know they won't melt like the other silver contacts.

Thanks in advance for anyone's help... 8)

 

[Lou]

Nitric acid solution for the Ag-W. I'd throw away the Mo.

 

[goldsilverpro]

Sparky,

You shouldn't be melting silver contacts because many, but not all, contain cadmium, which can produce very toxic fumes when molten. The problem is that you don't know which ones do or which ones don't contain cadmium. That is just tempting fate. I used to run about 5 pounds of large silver contacts at a time. Every batch contained cadmium. To eliminate the cadmium, dissolve them in nitric and then cement the silver with copper.

 

[metatp]

I would use a dilute nitric acid with water (30/70 or less) and let them sit for a while. I would try a small batch first, because when I used 50/50 nitric/water, I had issues when cementing with silver. Some of the W/Mo (or byproduct of W/Mo) drop with the Ag. It was a dark purple color. It cleaned up with HCL, but I refined the resulted powder again just to be sure.

I now stay away for refining these type of contacts. I sell them on ebay as tungsten/silver composite that are 40-60% silver.

Again, I would try nitric on some first. Some of the tungsten composites stay intact and they cement well with copper.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=5728

Regards,
Tom

 

[Harold_V]

I processed a large amount of silver/tungsten contacts through the years. As has been suggested, dilute nitric will do an adequate job. Please note that I processed by heating.

The thicker tungsten contacts can take a few hours to leach to the center. You can easily tell when that has occurred by removing a sample, and attempting to break it in half with a thumb and finger, pressing the contact on a counter surface. If you have leached all of the silver, the contact will break easily. If you have not, should you manage to break the contact, the center, where you have not removed the silver, will be all too apparent by the dark line you'll see. Return the contact to the container and continue heating. It is a prolonged process, but you can extract, for all practical purposes, all of the silver.

Silver that is recovered with copper from this process will contain traces of tungsten. As has been noted, it can be washed with HCl, which yields a dark blue solution. Any remaining traces of the contaminant will be removed when melting with flux (borax). Such contacts are well worth processing, assuming you have a reasonably priced source for nitric.

Harold

 

[Anonymous]

I processed a large amount of silver/tungsten contacts through the years. As has been suggested, dilute nitric will do an adequate job. Please note that I processed by heating.

The thicker tungsten contacts can take a few hours to leach to the center. You can easily tell when that has occurred by removing a sample, and attempting to break it in half with a thumb and finger, pressing the contact on a counter surface. If you have leached all of the silver, the contact will break easily. If you have not, should you manage to break the contact, the center, where you have not removed the silver, will be all too apparent by the dark line you'll see. Return the contact to the container and continue heating. It is a prolonged process, but you can extract, for all practical purposes, all of the silver.

Silver that is recovered with copper from this process will contain traces of tungsten. As has been noted, it can be washed with HCl, which yields a dark blue solution. Any remaining traces of the contaminant will be removed when melting with flux (borax). Such contacts are well worth processing, assuming you have a reasonably priced source for nitric.

Harold

Thanks,

I got a 4 pound lot of tungsten/silver contacts yesterday...
I placed some of the contacts in a 50/50 solution yesterday...and applied heat. after 6 to 7 hours some white cloudy crystals/flakes formed on the outside edge of my container. I let it set overnight without heat.

this morning I pulled some of the contacts to test if the break easy and about half of them do. Some of the have a reddish color pastie film on them... sorta like rust. These don't seam to break... the outside crumbles off but what is left is a paper thin sheet of black colored flexible metal. And the ones that are hard to break still have a light color inside...(silver)

The reaction stops after I remove the container from the heat.

What is the crystals/flakes?

What is this paper thin sheet of black colored flexible metal?

After the diluted solution sits is a greenish blue in color with a gray powder at the bottom. If i stir it turns a greenish gray. The contacts are still in the solution.

I know I need to remove the contacts before I place the copper bar to cement, but do I need to filter off the gray powder and the crystals?

Do I need to dilute the solution before I place the copper for cementing?

Thanks, David

 

[Barren Realms 007]

Filter your solution before adding your copper to cement or you will have to deal with the residue again. No need to dilute your solution.

 

[Anonymous]

Filter your solution before adding your copper to cement or you will have to deal with the residue again. No need to dilute your solution.

Thanks.

That means the silver is in the solution...

Any idea what the crystals/flakes are?

Does the crystals/flakes have any value?

Does this gray powder have any value?

Thanks, David

 

[Barren Realms 007]

The silver should be in your solution. Take a little bit of your acid and put a piece or 2 of urea to see if you get any reaction. If you get a reaction you still have nitric and everything that was going to dissolve should have. If you don't get a reaction then you should siphon off the solution and run the solids in some more nitric till no more reaction. I am assuming you are adding heat to this to help with th reaction?

 

[Harold_V]

If you get a reaction you still have nitric and everything that was going to dissolve should have.

That may not be true. As the silver is dissolved, the remaining "skin", for lack of a better description, forms an isolating shell around the remaining values. Acid can, and will, penetrate, but it's a slow process. It is for that reason that I suggest heating, and for a prolonged period of time.

My procedure was to boil continually, covering with a watch glass. When no brown fumes came off, I poured in cold water, to cool the contents, then quickly poured off all of the solution to a second beaker, where it was allowed to settle. Once the beaker was empty of fluid, it is easy to remove a sample to do the break test. If any are found to still have a hard center, more acid and water is introduced, and heated to boiling. The boiling action keeps the resulting solids in suspension, allowing the fluid to make intimate contact with the pieces that still contain silver.

I insured that I poured off any of the light weight solids that resulted from dissolution of silver. It was these solids that were allowed to settle in the second beaker. Eliminating them from the first vessel insures that contacts at the bottom are not isolated from contact with fresh acid.

It isn't necessary to filter the solution, assuming the solution is allowed to settle well. Traces of solids may be carried to the cementing stage, but they will be removed by flux (borax) when melting the silver in preparation for parting in a silver cell.

Harold

 

[Barren Realms 007]

I forgot to add that to the equation, thanks Harold.

 

[Harold_V]

That means the silver is in the solution...

Not necessarily

Any idea what the crystals/flakes are?

If you have allowed your solution to cool, it's likely the crystals you speak of are silver nitrate. It is for that reason I suggest that you pour in cold water before pouring off the solution when nitric has been exhausted. By diluting, you won't get the crystal growth. When your solution is cool, it should be a pale blue/green color, with cream colored particulate matter on the bottom. If you see any crystal growth, add more water.

Does the crystals/flakes have any value?

See above

Does this gray powder have any value?

If nothing else, it will contain silver in solution. It should be well rinsed with distilled water if you'd like to extract all of the values.
While tungsten has considerable value, unless you have a substantial amount of this residue, I expect it will have no further value to you. It is unlikely you could find a buyer. In my case, it was added to my waste materials. I used tap water, so I always had traces of silver cloride in my solutions. Values were recovered when I processed my wastes, with the residues absorbed by the flux. That may not be in your future, so you may be better served to rinse well.

Harold

 

[Barren Realms 007]

How would the tungeston be refined for sale? And what quantity would have to be produced for a buyer to be interested in purchasing it?

 

[Harold_V]

The makers of tungsten carbide insert tooling would be a likely place to sell--they already buy scrap tungsten, but I am unaware if they will deal with chemically altered tungsten.

They pay in the $7/lb range for scrap carbide. Don't know anything more, and I've never tried to sell any. I tossed all of my scrap when I sold the refining business.

Harold