Adas
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Sodium hydroxide reacting with hot carbon?
Hello everyone, happy new year!
Today I noticed something very strange - that when I throw NaOH pellets into a fire on hot coal, then in melts and starts to bubble violently. The
bubbles appear to ignite when they come to contact with air and I hear a popping sound. The NaOH just seems to be "burned away" and it "eats" some of
the coal.
What reactions are going on? It pretty much looks like the NaOH acts as an oxidizer. Does anybody have a clue?
Rest In Pieces!
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watson.fawkes
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Quote: Originally posted by Adas  | | Today I noticed something very strange - that when I throw NaOH pellets into a fire on hot coal, then in melts and starts to bubble violently. The
bubbles appear to ignite when they come to contact with air and I hear a popping sound. The NaOH just seems to be "burned away" and it "eats" some of
the coal. |
I would have to guess that hot molten base is a very good depolymerizer of cellulosic material,
even when charred, and so also accelerates the release of methanol as by dry distillation. Young charcoal, not fully burned out as you'd get in a
roaring fire, still has quite a high percentage of non-carbon left in it.
You could test this guess by putting a small square of graphite into the same fire and melting some NaOH on it, to see if you get a similar reaction.
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12AX7
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Worst case, sodium is a known product -- reduction usually involves the carbonate and yellow-white (>1200C) heat, though. The sodium, which is
gaseous at such temperatures, would burn immediately in a fire, simply producing more orange glow, so if it were there, you wouldn't really know it.
It would react fairly rapidly with nearby CO2, which would liberate a little H2O:
2 NaOH + CO2 = H2O + Na2CO3
At sufficient temperatures, the H2O will oxidize carbon, producing hydrogen and carbon monoxide; these later burn with more oxygen.
NaOH may effect reactions on the gasses and smoke coming from, or through, the charcoal, I suppose things like decarboxylation and dehydration. It
would also fizz just from gasses bubbling through it.
Tim
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Adas
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Watson, that seems plausible, but I have no graphite squares or anything like that. But I noticed that this violent bubbling and popping only occurs
at temperatures, where the coal glows pretty much. Otherwise it just melts and evaporates after a while. It needs to be orange-hot.
12AX7, the temperature was far below 1200°C. I even doubt that it was enough to react H2O with carbon.
Rest In Pieces!
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12AX7
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IIRC, orange-hot is sufficient for reaction with steam?
Don't forget that it's in concentrated form: even though there isn't all that much H2O in NaOH, and it's not the most available (it's not just
chemically bound water "Na2O.H2O"), and the reaction isn't the most energetic (C + O2 is a lot better), it's still ~a thousand times more concentrated
than steam, and thus a lot more likely to occur, even at lower temperatures.
Tim
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