# removing gold from tungston crucible



## andycourson (Dec 6, 2008)

I have a tungston crucible that cracked and cant be used any more. when it cracked some gold leaked out and is all over the side and a good coating inside as well. this crucible weighs a lot as there is a lot of tungston there. i dont want to set up a electro cell just to get this gold maby 3-4g. would hot hcl attack this? would ap be better? any ideas? would ap get under the gold and lift it off like gold fingers?


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## Harold_V (Dec 6, 2008)

andycourson said:


> I have a tungston crucible that cracked and cant be used any more. when it cracked some gold leaked out and is all over the side and a good coating inside as well.



Blink! Blink! :shock: :shock: :shock: 

You're joking, right?

Harold


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## lazersteve (Dec 6, 2008)

You should be able to remove the gold by attacking the Tungsten using hot HCl or concentrated peroxide. 

Steve


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## Lou (Dec 6, 2008)

I see this type of silliness all the time! People that want to melt precious metals in other metal containers, usually tungsten, molybdenum, or tantalum. 


I even had someone send me a platinum crucible that they had tried to melt platinum in!!


As for your problem, trying to dissolve away the tungsten with hot HCl or with electrolysis in conc. NaOH will take forever and a year. KNO3 and KOH also work, when molten. It's a real bother...


If I had to use anything though, it would be 30% hydrogen peroxide--Steve gave good advice. A mixture of 50:50 HF/HNO3 attacks tungsten readily; plain HF does too, so long as the metal isn't in bulk (i.e. powder, turnings, thin sheet works best!).

Supposedly, there is another electrolytic route that uses ammonia and ammonium nitrate as the bath. US patent 4283258


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## andycourson (Dec 6, 2008)

the crucible gets used in a vac deposition machine. I wasnt using it to melt gold personally. after many uses sometimes the crucible cracks and this is the result. there is usually 50-60g melted in this and that is our gold sorce for e-beam deposition. this one cracked before I started working there. my boss gave me this when he found out my new interest in refining/reclaimation. he said when I get it off I have to buy lunch for the guys. seems like a fair trade.


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## qst42know (Dec 6, 2008)

Lou.

Would this be a good application for the vitreous carbon crucibles you had your eye on? Not for recovering this but in place of the tungsten?


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## Lou (Dec 7, 2008)

Yes. At the temperatures employed they offer no contamination and minimum vapor pressure.


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## goldsilverpro (Dec 15, 2008)

I agree with the 30% peroxide. It was one of the few ways that worked for removing the W from W/Ag contact points.


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## butcher (Dec 16, 2008)

Andy any followup on your progress with this? I kinda thought that old crucible could be used in an electrolytic cell project.


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## NobleMetalsRecovery (Dec 16, 2008)

Has anyone done this yet? I'd like to know how fast it works. I have 35% H2O2. Would it dissolve Tungsten carbide? Do you just use straight H2O2?


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## Lou (Dec 16, 2008)

I don't think it'll touch WC which is very inert.

As for how fast peroxide dissolves tungsten metal, well that depends on a host of factors, namely:

temperature
concentration
surface area
degree of solution agitation

I'd have to consult some literature to get a sure fire method for handling tungsten carbide.


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## andycourson (Dec 16, 2008)

I tried hot hcl with no luck, then hot hcl and 30% h2o2 this worked for a while disolving the thin coating of gold but without much affect to the thicker parts. the crucible started to dissolve and the outside became green. i got impatient with how long it was taking, and how i had to keep adding h2o2 to keep the reaction going. i then took out the crucible and started to break it in to pieces with vicegrips this worked very well because the tungston is brittle. so i got rid of everything that didnt have gold on it. i then used AR on it this seemed to leave the tungston alone and just disolve the gold. I wish i would have just put in AR to begin with. I ended up with 5 g of gold


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## Harold_V (Dec 17, 2008)

Lou said:


> I'd have to consult some literature to get a sure fire method for handling tungsten carbide.



I didn't get the impression it was tungsten carbide, just tungsten. 

Harold


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## NobleMetalsRecovery (Dec 17, 2008)

Sorry for the confusion on this. My original question was regarding plain Tungsten, then as an afterthought I also wondered about tungsten carbide, and tungsten alloys in general.


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## Lou (Dec 17, 2008)

@Harold, Noble Metals Recovery inquired about dealing with WC.


@andy, you did probably the smartest thing to do and what we all (I think) overlooked: increase the surface area!!

Aqua regia does attack tungsten, but it quickly makes a passivated coating and does no further damage.


Lou


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## andycourson (Dec 17, 2008)

that makes sense there was a definately a yellow/green coating on the crucible (actually at this point it is just a bunch of small pieces so it is really not a crucible anymore). When i took the pieces out of the AR the places where the gold was looked untouched, it was still shiny tungston. probably because i used very little nitric and it was all used up after the gold had dissolved.


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## DNIndustry (Dec 27, 2008)

Im going to get beat up for saying it but NH4I/I2/h202. The tungsten would be minimally attacked if at all, just the gold. The process is used in thin film circuit etching quite frequently. But if you dont have I2 already, it would be difficult to aquire.


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