(Revisited) Making Elemental Potassium (K)


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:

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.