Disclaimer:
All experiments in this text should be done outside or in a fume hood
with proper lab and safety equipment. It must be done by or under the
direct supervision of someone experienced with chemistry laboratory
procedures. These procedures must never be done in the presence of
young children or animals.
First I want to thank the many contributors on ScienceMadness, as
their procedures and successes are what helped me achieve success with
this reaction. Credit is also owed to the author of the thread at
http://www.versuchschemie.de/topic,14677,-Synthese+von+Kalium.html.
In this re-visitation of the synthesis of elemental Potassium I used Tetralin and t-Amyl
alcohol as opposed to ultra pure paraffin oil and t-butanol in my first attempts.
Due to Tetralin's high density (0.97g/ml), it being higher than
potassium itself (0.89g/ml), it allows the molten potassium to float on
the surface, separating it from the magnesium metal and magnesium oxide
formed in the reaction which have a greater density and therefore
remain at the bottom of the reaction vessel.
So
here is the outline in my lab book for the procedure:
The
reactants were as follows:
2g
high purity Mg. approx 75 mesh, very low oxide. ( I actually made this
immediately before the reaction from a high purity ingot) You can
produce this with a medium metal file or as I did using a milling
machine to produce very fine turnings. My source for the Magnesium was
an Amazon seller named GalliumSource who sells small 99.9% pure
magnesium ingots. I highly recommend using Magnesium of this purity, as
lower puritys I tested did not produce success. Magnesium
Metal Ingot, 99.95% Pure, 8 Ounces
Be aware that tetralin really smells horrible and is a potential carcinogen! Just like
naphthalene moth balls (kind of a DUH! statement there...) which is now
on my sh*t list of smells. Really got sickening when cleaning up my
glassware. Anyways, here are the photos of the reaction:
A color change of my solvent was
noted nearly as soon as it heated up. this eventually dissipated.
Soon after, extremely tiny potassium globules could be seen all over
the surface of the Mg
turnings. Its not very visible in this picture, but I am including it
for completeness.
After some time, there were some large balls of potassium forming,
however, they were refusing
to float as they should have (I believe it may have been oxides
weighing the globules down)
Soon after the first 'floaters' appeared:
And finally, the end results! Several large balls of pure elemental
Potassium, along with one which
I had to highly deform in order to get it out of the reaction vessel.
Yes, it was too large to fit!
Total reaction time was approximately 4 hours.
The Potassium is being stored under heavy mineral oil temporarily until
vacuum or inert atmosphere ampouling.
Conclusion:
Utilizing a solvent that has a greater density that potassium is an
excellent way to further increase the yield of this reaction.
