Conure
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Good way to thermally decompose ammonium molybdate?
I'm trying to make MoO3. I tried putting some ammonium molybdate in a steel vessel over a burner. The temp from the red hot bottom of the vessel is
barely enough to turn the white powder into yellow MoO3. It requires lots of tedious stirring, otherwise it just goes from white to dull green. Is
there a better method? Do I need a furnace, a lab oven or a powerful hot plate?
[Edited on 22-6-2024 by Conure]
[Edited on 22-6-2024 by Conure]
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EF2000
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Brauer's Handbook of Preparative Inorganic Chemistry recommends first reacting ammonium molybdate with nitric acid (maybe other reasonably
strong acids can be used), then decomposing resulting molybdic acid (drying hydrated molybdenum trioxide) at about 150 °C for 16-20 hours: page 1412
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Bedlasky
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When I did decomposition of ammonium heptamolybdate, the resulting MoO3 always turned blue, indicating some MoO(3-x) contamination. I once saw jar
with ammonium molybdate which had slightly blue hue. I look in to some papers and according to their analysis, decomposition in air should make pure
MoO3 because of oxidizing power of O2. I did decomposition on hot plate, so maybe lower temperature favor uncomplete decomposition and partial
reduction???? Who knows. For what purpose do you need MoO3?
https://core.ac.uk/download/pdf/42943961.pdf
[Edited on 22-6-2024 by Bedlasky]
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Conure
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It sometimes turn blue-black if the temp is not high enough. I get black spots in my powder.
I want to do thermitic reactions with MoO3 because it seems like a good alternative to Fe2O3, especially if with more exotic fuels. I have bought MoO3
from onyxmet.com but the purity keeps going down, my last order was dull green with garbage performance. And the price keeps increasing.
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Conure
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Quote: Originally posted by EF2000  | | Brauer's Handbook of Preparative Inorganic Chemistry recommends first reacting ammonium molybdate with nitric acid (maybe other reasonably
strong acids can be used), then decomposing resulting molybdic acid (drying hydrated molybdenum trioxide) at about 150 °C for 16-20 hours: page 1412 |
Using molybdic acid is just as tiresome, I have tested. It requires high temp.
Fire is good. Fire is life.
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