To use a personal anecdote, it took me 10 tries to get K using this method, each using a slightly different setup than the last. On attempt #8, I
noted that while I had gotten potassium, it only came as a few very tiny spheres among a pile of still-unreacted KOH and Mg. I later found that this
was due to catalyst freezing in the condenser above the flask, unable to react further with the mixture. While that doesn't quite carry over for
NurdRage's setup, the point is that such minute details can easily cause someone to think something isn't working very well, or is only working
slowly.
I would note that his use of mineral oil was something I discontinued around attempt #5, as it proved too unpredictable of a solvent for me to work
with. Kerosene proved to be a much better alternative. I also agree with his observation that alkali metals perform this reaction faster with
increasing 'reactivity' (there's a graph to be made there, to be honest, but it would probably place lithium firmly at the ass-end of an exponential
curve, requiring thousands of hours of heating to complete the reaction).
I'd also like to note a critical detail NurdRage may have overlooked (which may be partially responsible for low reaction rates): Work by Dan Vizine
on this forum on ampouling and containing Li revealed that it cannot be melted in a glass ampoule, due to immediately reacting with the glass. I think
what might be happening is that any Li that is being formed is immediately melting and hitting the glass walls, promptly turning into lithium
silicate. However, this is countered by his observation that the glass flask used for the molten LiOH/Mg mixture remained untouched at the end of the
trial runs, meaning no significant amount of Li had been produced to react with it in the first place. I wonder if switching container material would
result in an improvement? |