metalresearcher - 26-2-2025 at 10:46
Last summer I isolated some K metal which I still have in a jar with mineral oil. I want to put a few milliliters into an ampoule. I have a 10mm ID
borosilicate glass tube which I already closed off at one end and narrowed a bit close to the other end (see photo 1) which will be the ampoule.
My plan is:
* melting the K in a beaker or test tube using a heatgun
* put the still open ampoule in a lab stand and flush it with argon
* sucking up the K using a pipet and a rubber suction bulb (see photo 2)
* dumping the still liquid K into the open ampoule (the end of the pipet fits in the mouth of the ampoule)
* light a propane burner and heat the narrowed part and close it, while keeping it vertical
* let it cool slowly.
The issues I expect are that : can borosilicate glass withstand molten K ? Or will it try to reduce the silicon from the SiO2 in the glass ?
Does anyone have experience in this ?
Sir_Gawain - 26-2-2025 at 10:59
Molten potassium and glass is fine at these temperatures. This method should work, but if you want pure, shiny potassium you need to vacuum distill it
into the ampoule.
SuperOxide - 27-2-2025 at 05:27
AdvancedTinkering on Youtube has some great videos on the subject, and even one on how to purify it without distillation. Seems reasonably effective.
But, as Sir_Gawain said, vacuum distilling it (after thoroughly drying everything) directly into an ampoule is really the best way (though I'm not
speaking from experience).
metalresearcher - 27-2-2025 at 09:49
SuperOxide, I have viewed that video. It requires glass blowing equipment using a special burner with extra oxygen.
davidfetter - 27-2-2025 at 12:50
Yes, it does.
When you're messing with something like pure potassium, you will need specialty materials like borosilicate glass, and special tools like those needed
to shape it. Just think how little fun it would be if you had to figure out how to do this with soda lime glass, or slump your own borosilicate.