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Ben Messaoud.F
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Vanadium oxides, etc.
Dear All
I wonder if there is a green vanadium oxide.
Thanks
Ben Messaoud.F
(Edit by Nicodem: Made the tittle descriptive of the topic.)
[Edited on 2/7/2009 by Nicodem]
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DJF90
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This should be in the short questions thread located in the miscellaneous forum. Have you tried a google search first?
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Ben Messaoud.F
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I really tried on google but I have not found
I have a vanadium compound green, it is neither V2S3 or V2S5. Some said it may be V2O3. But that is not on the fact that this compound is generally
gray. For this reason I will use this forum to find the relevant answer
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hissingnoise
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According to WebElements, VO can be black, grey or green; light green is given as the colour for VCl2. . .
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DJF90
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Here's the green vanadium compounds I could find from Brauer:
Vanadium (III) chloride hexahydrate: Green, hygroscopic crystals.
Vanadium (III) bromide: Black with greenish reflections, crystalline; the vapor is violet.
Extremely hygroscopic, d 4.52.
Vanadium oxydichloride (VOCl2): Shiny green crystals; hygroscopic,
d 2.88.
Hydrogen Disulfatovanadate (III) HV(SO4)2 • 4 H2O: Green crystalline powder; can be
stored for extended periods of time in closed bottles even in the
presence of air.
Ammonium and Potassium Disulfatovanadate (III), NH4V(SO4)2, KV(SO4)2: Green, crystalline powder. Insoluble in H2O and acids; attacked and decomposed
by alkali.
Vanadium (IV) Oxysulfate (Vanadyl Sulfate) VOSO4 (anhydrous): Green, loose, granular to finely crystalline powder; virtually insoluble in H2O.
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Ben Messaoud.F
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I wonder if V2O3 drink or not and in those circumstances can it give a green knowing that V3 + is green
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merrlin
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Many oxides change color when they go off stoichiometry. If vanadium pentoxide is partially reduced it can take on a green color. As indicated in the
other posts, trivalent vanadium is often associated with green. You might try heating it in oxygen or air and see if it changes to black or brown.
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Ben Messaoud.F
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I heated the compound at 250 ° C for 36 h, the compound takes the green- yellow color.
. What can it be?
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hissingnoise
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It's hard to say for sure---V2O5 mixed with lower oxides, possibly. . .
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Ben Messaoud.F
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If we increase the temperature to 600 ° C which form vanadium V2 +, V3 +, V4 + or V5 + is formed in solid material
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not_important
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Heating with ready access to air? No contact with gases from flame used to heat? A fairly thin layer?
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woelen
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If vanadium oxide is strongly heated in contact with air, then black VO2 is formed (+4 oxidation state). I tried this myself, by heating V2O5 very
strongly and then dissolving the remains in acid, which gives a blue solution, with a greenish tinge (most likely due to the presence of left over
V2O5).
[Edited on 6-6-09 by woelen]
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merrlin
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Quote: Originally posted by woelen  | If vanadium oxide is strongly heated in contact with air, then black VO2 is formed (+4 oxidation state). I tried this myself, by heating V2O5 very
strongly and then dissolving the remains in acid, which gives a blue solution, with a greenish tinge (most likely due to the presence of left over
V2O5).
[Edited on 6-6-09 by woelen] |
What temperature did you use? Attached are some phase diagrams scanned from a 1975 reference. As indicated in the text, vanadium oxide heated in air
at 600 degrees Celsius (or lower) should produce stoichiometric vanadium pentoxide. Increasing temperature and/or decreasing oxygen partial pressure
will tend to produce a suboxide. Small amounts of substitutional impurities in oxides can also alter the expected color (e.g., chromium for aluminum
in sapphire gives ruby).
Attachment: V-O_phase_diagram.pdf (94kB)
This file has been downloaded 579 times
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Ben Messaoud.F
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The document is attached by Merrlin interest, but I will know if oxides retain the same physical properties when they react with solid
précurseurs. other words, if one starts with V2O5 or V2O3 with other precursors such as NaH2PO4 and G2O3 or for example at 600 ° C in air, the
vanadium compound involved in the final is a V2 + V3 +, V4 + or V5 +?
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woelen
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@merrlin: I heated in the roaring flame of a butane torch in a special heat-resistant supramax test tube. I cannot measure the temperature of such a
flame, but I would not be surprised if the temperature of this is well beyond 600 C.
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Ben Messaoud.F
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thank you for the link, I saw above that describes the color of the ions in a liquid solution, but what I want is the behavior of vanadium in solid
solution
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not_important
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| Quote: Originally posted by Ben Messaoud.F | | thank you for the link, I saw above that describes the color of the ions in a liquid solution, but what I want is the behavior of vanadium in solid
solution |
There is no simple response to this, it depends on what else is making up the solid solution, the redox conditions, the temperature profile, and other
variables.
In a simpler case, Mn(II) is normally pale to moderate pink, however in a tetrahedral environment such as solution in zinc silicate Mn(II) is an
intense fluorescent yellow-green. I've seen a piece of pottery dipped in a vanadium glaze end up after firing with just about every shade of the
spectrum in the glaze, just from the local redox, temperature, and glaze thickness.
Go to the Internet Archives and download a mineralogy book or two, and check the bead tests for vanadium to get a start at getting an answer to your
question. Alexander Hamilton Phillips book is a decent starter, as it includes a series of tests for most metals.
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Ben Messaoud.F
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I will know if oxides retain the same physical properties when they react with solid précurseurs. other words, if one starts with V2O5 or V2O3 with
other precursors such as NaH2PO4 and G2O3 or for example at 600 ° C in air, the vanadium compound involved in the final is a V2 + V3 +, V4 + or V5 +?
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merrlin
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If an impurity combines with vanadium oxide to form another additional oxide phase you may get vanadium with different valences. Substitution by
impurities may also affect the valence balance in the vanadium oxide. You might also want to Google: +intercalation +"vanadium pentoxide."
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Ben Messaoud.F
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if mixture G2O3 And V2O5 and KH2PO4 to 600 ° C under air, what is the formula of the compound that can be obtained?
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not_important
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What is G2O3? It's not IUPAC symbol based, nor does it fit in the Dorseyville Middle School naming system.
Why do you believe that that mixture will form a compound. I can tell you that 500 tonnes of V2O5 plus 1 ng each of the other two will give you V2O5,
which can be fused without decomposition at 690 C.
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Ben Messaoud.F
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@not_important posted on 11-6-2009 at 06:59
when we talk about Gd2O3, it is well known that this oxide Gadolinium and if we speak a mixture of V2O5 and KH2PO4 and GdO3, but a stoichiometric
mixture and not a mass of 500 tonne Booster of.
.. and 1ng of ...
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Nicodem
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Ben Messaoud.F, you obviously do not ask these questions in the context of amateur chemistry (which this forum is about in case you have not noticed
yet), so I have to ask you why don't you just do a powder XRD of your samples and do a spectral identification by comparison with a database? If you
don't have access to powder X-ray diffraction, then ask someone to do it for you (it doesn't take much).
There are also a couple of methods to find out what is the oxidation state of metals in the materials. Using an electron microscope (SEM, XPS, etc.)
you can even check the composition and oxidation states in each phase (if your material is polyphasic). Posing your questions on an internet forum is
barely any more reasonable than asking a fortune teller. The only reasonable thing to do is to do research work.
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Ben Messaoud.F
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Exactly what I do, but the identification of phases by the Rietveld method is sensitive I was not really able to determine the formula of my compound.
For this reason I have asked in the topical cristallography appointed in the same forum on the intercalation of the formula in Fullprof. Thanks
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not_important
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But all your previous postings use G2O3, not Gd2O3, I do not believe that making assumptions about lazy typing habits is the
best way to proceed.
| Quote: | | and if we speak a mixture of V2O5 and KH2PO4 and GdO3, but a stoichiometric mixture ... |
The V-P-rare earth phosphors seem to have their formula given as K3R[1 – y] Eu [y] (PO4) [x] (VO4)[2 – x ], which is hardly a simple
stoichiometric formula, and would not readily match up with your starting materials. The vanadium does appear to be present entirely as V(V), from
most reports.
If this is not your target then it would have been helpful, and indeed even intelligent, to have stated the proportions of the starting compounds
rather than having readers guess at what you are trying to do.
The phases, and possible compounds, present in these sorts of mixtures can be far from a simple question. The only study I remember seeing phase
diagrams for was a V-Ce-P oxide catalyst, the V-P axis included phases with V
ratios of 18:1 to 1:5. There were over 30 phases total, with some phases only stable at higher temperatures so grains of them would transform into
mixtures of other phases on cooling. With this mix they were dealing with Ce(III) and Ce(IV) as well as V(IV) and V(V), likely much more complicated
than your case but still suggesting that you may not be dealing with a simple compound but rather a mixture.
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