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MR AZIDE
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[*] posted on 28-6-2012 at 16:29
Molybdenum metal.



Has anyone ever collected blown tungsten filament bulbs, bust them open and collected enough of the fine support wires that are supposedly made of Molybdenum, to make any compounds from the Molybdenum?


Maybe some didn't realize the the supporting wires for the filament are made of Mo??????

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DoctorOfPhilosophy
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[*] posted on 28-6-2012 at 20:55


Yep, I used to pull burnt/broken halogen lights from a construction site and pull out the W and Mo. I'm not sure if it's Mo, but they're still lying in my periodic table so if you propose a test I'll post the results.
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vmelkon
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[*] posted on 29-6-2012 at 03:52


Quote: Originally posted by MR AZIDE  

Maybe some didn't realize the the supporting wires for the filament are made of Mo??????


You mean the thin wires that support the filament?
http://www.ehow.com/list_6623245_minerals-light-bulb_.html

Since when have they been using Mo? I had not heard about it previously.

More stuff
http://www.ushio.com/support/faqs.htm

"Why is molybdenum foil used inside the halogen lamp?
Molybdenum foils is used as a conductor through the seal part of lamp. It insures the hermetic sealing of the lamp. Molybdenum has almost the same thermal expansion properties as quartz. "

[Edited on 29-6-2012 by vmelkon]
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Endimion17
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[*] posted on 29-6-2012 at 04:21


I've heard about molybdenum being used for filament support a long time ago (pure or alloyed, don't know), but I've also read somewhere it's not being used anymore. That's all I can tell at this point.



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daragh8008
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[*] posted on 29-6-2012 at 04:53


I have lots of Molybdenum metal coated with gold. We use it for our gold evaporator and when it blows we just keep it. Wouldn't anyone have any easy methods of separating the gold from the Mo metal for recovery??
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blogfast25
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[*] posted on 29-6-2012 at 05:18


Treatment with Aqua Regia and precipitation of the Au with sodium metabisulphite (after partial neutralisation) should work.



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plante1999
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[*] posted on 29-6-2012 at 05:57


Molybdenium is not very similar to gold, Maybe HCl/chlorine would only dissolve gold. Generaly when disolving gold plating we use 20% HCl with small amount of sodium hypochlorite in it to leach the gold.



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[*] posted on 29-6-2012 at 07:13


Grinding, then heating will release Mo trioxide, which evaporates above 1150*c, which is also slightly water soluble (yeilding molybdic acid).
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chornedsnorkack
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[*] posted on 30-6-2012 at 12:08


Molybdenum also dissolves in hydrofluoric/nitric acid mixture. At higher temperatures, molybdenum metal reacts with molten alkali and with molten alkali metal nitrates.
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cyanureeves
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[*] posted on 1-7-2012 at 10:17


daragh8008 you have lots? you mean plated?peroxide and hcl acid releases the gold from copper maybe it will do the same with molybdenum and maybe its got alot more gold surface than computer gold. if it doesnt peel the gold then aqua regia as suggested will do the trick. just let it evaporate after dissolving and add sodium metabisulfate.
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blogfast25
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[*] posted on 1-7-2012 at 11:15


Quote: Originally posted by cyanureeves  
daragh8008 you have lots? you mean plated?peroxide and hcl acid releases the gold from copper maybe it will do the same with molybdenum and maybe its got alot more gold surface than computer gold. if it doesnt peel the gold then aqua regia as suggested will do the trick. just let it evaporate after dissolving and add sodium metabisulfate.


"peroxide and hcl acid releases the gold from copper maybe it will do the same with molybdenum"

What precisely do you understand by 'releases'?

And I do wish people wouldn't use LOLtext for chemical formulas ("hcl") :(

[Edited on 1-7-2012 by blogfast25]




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daragh8008
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[*] posted on 1-7-2012 at 12:47


Quote: Originally posted by cyanureeves  
daragh8008 you have lots? you mean plated?


I suppose I should clarify what I meant. the coater takes a strip of Mo about 3cm by 1cm formed into a little boat. We buy in sheets of the stuff and shape it ourself. I'm not sure what the thickness of the sheet is but somewhere around 0.2 - 0.5 mm. I have at least 20 used boat of Mo almost all with gold left in them. In some the gold is very little as Au is generally green when it is thiner than about 10nm in others there appears to be up 1-2mm of gold stuck to the Mo metal when the boat went. It would be nice to just release the gold from the Mo. I may try the peroxide hcl method first. I don't have any nitric acid but I often work with molten nitrates so I may give that a shout also. I did once also dissolve very thin coatings of gold with NaCl solution and a Hg lamp, these were however very thin sputtered gold coatings ~1-2nm so I don't think that would be a route. I suppose Aqua Regia is the best was but I don't have any nitric acid so for the time being it is not an option.
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cyanureeves
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[*] posted on 1-7-2012 at 17:11


daragh8008 thank you for that information. i have plated gold items and have gotten a greenish hue before,very interesting.
@blogfast by releases i meant that gold will separate as foils and float around in the sloution and i dont really know how it happens. do you mean HCl does not need the word acid next to it?ha.ha i understand:D

[Edited on 2-7-2012 by cyanureeves]
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blogfast25
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[*] posted on 2-7-2012 at 04:31


Quote: Originally posted by cyanureeves  

@blogfast by releases i meant that gold will separate as foils and float around in the sloution and i dont really know how it happens.


In all likelihood the HCl/peroxide mixture attacks the underlying metal slightly, thus destroying any bonding between the gold plating and the bulk metal. Some gold recoverers (from e-waste) use nitric acid to release the gold coatings from their substrates.




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daragh8008
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[*] posted on 2-7-2012 at 13:43


So I don't know much about Mo, would it be attacked by HCl / peroxide mix? I always assumed Mo was used as it fairly resistant to oxidation thus the peroxide would be fairly useless. ( although I often use this mix for etching Cu2O to good effect) @ cyanureeves : what we find is that glass coated with thin layers by evaporation are green but when the excess gold is peeled from the evaporator instrument it has the usual gold colour with a green hue. Because it is built up of dozens of coats it is very flaky. I assume between coats atmospheric contaminants build up to separate the next evaporated layer. giving it it's flaky texture and greenish hue
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[*] posted on 3-7-2012 at 05:00


Quote: Originally posted by daragh8008  
So I don't know much about Mo, would it be attacked by HCl / peroxide mix?


I would expect attack to be minimal.




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[*] posted on 6-8-2012 at 15:00


Quote:
Maybe some didn't realize the the supporting wires for the filament are made of Mo??????



In this 'How it's made - Incandescent Light Bulb' video they don't say what the wires themselves are made of, but do say that they are coated with zirconium:

http://www.youtube.com/watch?v=BylLOWRojyY&feature=g-vre...




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[*] posted on 22-3-2014 at 20:11


I did pull out a few support wires from lightbulbs, and bought a rod of molybdenum to compare. Two years later, both have the exact same black tarnish, so it's not steel or tungsten.

[Edited on 3-23-2014 by elementcollector1]




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[*] posted on 22-3-2014 at 20:14


Wow, that's awesome. I accidentally broke a lightbulb earlier today and saved the tungsten, but I had no idea the those support wires were Mo! I would have thrown it away otherwise. That's great!

Edit: Also, the lightbulb that I broke was a couple years old and the support wires also appear to have that black tarnish that you describe.

[Edited on 3-23-2014 by zts16]
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[*] posted on 22-3-2014 at 21:16


Yes, that is very useful, anther addition to my periodic table:D.
But, is there any way to chemically test the filament support to determine is it is molybdenum besides waiting several years for it to gain the black coating?




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[*] posted on 22-3-2014 at 21:42


I don't know… I just went looking for information about reactions involving metallic Mo, but with very little luck. If you heat it to above 600˚C it will form molybdenum trioxide according to Wikipedia, which has conflicting information as to what MoO3 actually looks like, since they have a picture of a gray powder, but say that it is either yellow or blue.
My chemical reference book says that it's whitish yellow, so I'd go with that. It also says that molybdenum metal has a density of 10.2 g/cc, if you have enough to measure that.
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