Keras
National Hazard
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Sodium hypomanganate
Folks,
For fun, I tried to mix molten sodium hydroxide with manganese dioxide. I had read somewhere it didn't end up forming Mn VI, but Mn V compound?
So I put a liberal amount (read: a few grams) of sodium dioxide in a crucible and when it was melted, I added max. one gram of manganese dioxide from
a now disposed of alkaline battery.
And… it does indeed, if the blue colour on the walls of the crucible is anything to judge by. But my crucible broke when it cooled. (Apparently
better transfer sodium hydroxide while liquid, it expands on cooling.)
There was, however, nothing much to write home about. I tried to leach the blue compound using water, but it must have disproportioned back into
manganese dioxide because all I got was dusty water with a slight yellow/brown tinge. The bottom of the crucible (which cracked) was caked with a
solid chunk of what I assume was manganese dioxide trapped in frozen sodium hydroxide. Apparently, the reaction (at least when oxygen from air is used
as the oxidant) is either slow, or very low yielding.
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Bedlasky
International Hazard
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Hypomanganates are very sensitive, they are somewhat stable only in very strong hydroxide solutions. Leaching in to the water destroy any
hypomanganate and manganate.
Hypomanganate is formed together with manganate by aerial oxidation of suspension of MnO2 in molten hydroxide. If you want manganate, use KNO3 as
oxidiser. Hypomanganates are very sensitive, I read thesis about preparation of hypomanganates, manganates and permanganates from melts, MnO2 + KOH +
air method give 19% K3MnO4 max. Better method is MnCO3 + K2CO3 + dry air method, reaction time 60 hours, cooling of the product under dry nitrogen,
this can give you 57% K3MnO4. So there isn't easy method with high yields for hypomanganates. Thesis is only in Czech, I can give link here for anyone
who understand and is interested in the topic, it is great source about hypomanganate and manganate chemistry.
https://dk.upce.cz/bitstream/handle/10195/19372/D10892.pdf?s...
Another interesting method is oxidation of MnO2 by NaNO2 in molten NaOH. I don't how pure product is, but there is definitely some hypomanganate
present.
https://www.sciencemadness.org/whisper/viewthread.php?tid=32...
If you want to play with hypomanganate, you can make solution of it quite easily. I described method here:
https://www.sciencemadness.org/whisper/viewthread.php?tid=32...
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Chemistryreacts
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The hypomanganate also forms from MnO2 + Na2CO3 in air with less fuss than using NaOH.
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Keras
National Hazard
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Interesting. Thanks for that. I will test it next weekend.
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