xfusion44
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Tungsten hexachloride production and its hydrolysis
Hi,
I tried to make some tungsten chloride with tungsten and HCl, but nothing happened, so I added some H2O2 and reaction started. As soon as I added
H2O2, reaction mixture turned beautiful blue color, which instantly dissapeared. With time, the mixture has turned slightly yellow in color, and I
could smell something that I believed was chlorine, but wasn't sure why this would happen. I've checked the wiki page about tungsten hexachloride and
it says, that this compound hydrolyzes in water and releases HCl. Now, I'm not sure what chloride of tungsten did I make (if it even was the one that
hydrolyzes) and what did I smell? Doesn't HCl have different smell, compared to Cl2? Also, what's the compound that gives yellow color in mixture - is
it product of WCl6 hydrolysis? And what could turn the mixture blue for a moment and would then dissapear?
Please help, I want to know what happened 
Thanks!
[Edited on 12-10-2015 by xfusion44]
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blogfast25
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WCl<sub>6</sub> can't be prepared by trying to dissolve W in HCl, not even remotely. Only direct union of the elements can achieve that,
in strictly anhydrous conditions.
WCl<sub>6</sub> would hydrolyse like mad at the mere sight of water! It's a predominantly covalent compound.
W is in general more or less impervious to acid attack. HCl + H2O2 will give some lower chloride that'll be quite prone to hydrolysis as well.
[Edited on 12-10-2015 by blogfast25]
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xfusion44
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Quote: Originally posted by blogfast25  | WCl<sub>6</sub> can be prepared by trying to dissolve W in HCl, not even remotely. Only direct union of the elements can achieve that, in
strictly anhydrous conditions.
WCl<sub>6</sub> would hydrolyse like mad at the mere sight of water! It's a predominantly covalent compound.
W is in general more or less impervious to acid attack. HCl + H2O2 will give some lower chloride that'll be quite prone to hydrolysis as well.
[Edited on 12-10-2015 by blogfast25] |
Oh, thanks for explanation. So, what would give yellow color to mixture?
Maybe I'll try to make it with anhydrous chlorine and some tungsten powder, hmm...
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woelen
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Is your tungsten powder pure? With H2O2 you get colorless compounds, based on tungsten(VI), such as H2WO4. With certain metals, these tungstate
compounds can be pale yellow, as is WO3.
Tungsten in lower oxidation state (+5, +4) only forms a few well-defined stoichiometric compounds. In water, these oxidation states can exist, but
only in ill-defined compounds with variable composition. These compounds have a blue color. It might be that you obtained these compounds transiently,
but it would surprise me. These compounds of tungsten with oxidation state lower than +6 are quite strong reductors and i would not expect them to be
formed at all in the presence of H2O2.
One way to make these compounds is adding zinc to an acidified solution of a tungstate. With molybdenum (the lighter congener of tungsten) the
production of these blue compounds works much better.
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xfusion44
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| Quote: Originally posted by woelen | Is your tungsten powder pure? With H2O2 you get colorless compounds, based on tungsten(VI), such as H2WO4. With certain metals, these tungstate
compounds can be pale yellow, as is WO3.
Tungsten in lower oxidation state (+5, +4) only forms a few well-defined stoichiometric compounds. In water, these oxidation states can exist, but
only in ill-defined compounds with variable composition. These compounds have a blue color. It might be that you obtained these compounds transiently,
but it would surprise me. These compounds of tungsten with oxidation state lower than +6 are quite strong reductors and i would not expect them to be
formed at all in the presence of H2O2.
One way to make these compounds is adding zinc to an acidified solution of a tungstate. With molybdenum (the lighter congener of tungsten) the
production of these blue compounds works much better. |
Thanks! Actually I don't yet have powder (I'd make it from solid tungsten). I'm not sure about purity, but I'm using electrode that's usually used for
TIG welder and is made of tungsten. Thanks for explanation
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