Making Elemental Potassium (K)


      I recently began a new hobby; collecting elements.  Of course with such a hobby comes a lot of chemistry. Especially due to the fact that whatever elements I can isolate by myself, I will. I believe it is much more fulfilling and educational to isolate an element yourself than just purchase it from some online retailer in a little vial or ampoule. Of course with chemistry there is inherent danger. So this disclaimer is necessary:

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,14677,-Synthese+von+Kalium.html.

I performed this reaction 5 times without success. My 6th and 7th attempts were successful. What I determined caused failure in reactions 1-5 was the use of impure (95%) magnesium.

Be sure to check out my latest and most successful attempt at isolating elemental Potasisum here: (Revisited) Making Elemental Potassium (K)

So here is the outline I wrote myself for the procedure:

The reactants were as follows:

I used a 50ml boiling flask, and a 200mm west condenser for reflux. I set my hot plate to 270*C and used a sand bath to heat the flask. A balloon with a small hole poked in it was fixed to the top of the condenser to minimize atmosphere from entering. Here is a picture of the setup:

First the Mg was added to the flask, then the KOH. The 35mL of paraffin was then added, and heated in the sand bath to drive off all water within the KOH due to its hygroscopic nature.

Note: The picture above shows the reactants from one of my first procedures (unsuccessful). The Magnesium
was only 95% pure which impeded the reaction, and the particle size of the both Mg and KOH was too large.

The Mg helps speed the displacement of water forming some MgO. Hydrogen evolution was noted in small quantities. After 30 minutes of heating, the t-butyl was added in small .1mL increments over the course of 2 hours. This was added by injecting through the balloon using a pipette to pierce the balloon and minimize atmospheric contamination. After 3 hours small globules of potassium were noted as seen below.


After 6 hours of reflux, the experiment was stopped, and allowed to cool. After cooling the reaction products were dumped into a large watch glass, and the potassium balls were extracted and stored under paraffin oil.

Final yield was very poor due to my not allowing the reaction to progress further upon which the potassium would have coalesced much more, but my time was limited. But I can now add potassium to my element collection!

Some Potentially Helpful Notes:

Here is how I prepare the Magnesium turnings. If you have a milling machine save your elbows some exhaustion! Please not that the Magnesium turnings must be protected from the atmosphere as soon as possible after being produced. I store it in sealed glass vials immediately after making it. I first secure the Mg ingot into my milling machines vise. After that I cut out a wide slit in the bottom of a cardboard water bottle tray and slid it over the exposed part of the Mg ingot. After setup I simply began milling a few thousandths off at a time very slowly to produce extremely fine turnings.


Solvents: It seems that certian solvents make this reaction occur with better yield and faster reaction times. Using paraffin, mineral oil, or a kerosene based solvent, the yield is approximately 50% at best, and with long reaction times (~4+ hours). When using solvents such as Shellsol D70, the reaction time is still long (~4 hours), but the yield is greatly improved with many experimenters reporting yields greater than 80%. Finally when Tetralin or Decalin are used, the reaction time seems to speed up greatly, and the yield is also high much like with Shellsol. Some report reaction times of approximately one hour using Tetralin.

      Conclusion: Although my production of elemental Potassium was successful, the final yield was very poor since my potassium refused to coalesce. This may be sue to my solvent or another unknown factor in my experiment. I will try to use different solvents in future replications of this synthesis in order to determine which solvents are most effective to promote potassium coalescence.