The following uses for potassium are gathered from a number of sources as well as from anecdotal comments. I'd be delighted to receive corrections as well as additional referenced uses (please use the feedback mechanism to add uses).
- The superoxide KO2 is used in breathing apparatus where moisture in the breath and carbon dioxide reacts with it to release oxygen [2KO2 + H2O + 2CO2 → 2KHCO3 + O2 ]
- the alloy of potassium with sodium (NaK) is used as a heat-transfer medium in nuclear reactors. The alloy is liquid at ambient temperature and is a good reducing agent in the chemistry laboratory
- fertilizers - usually as the chloride, sulphate, nitrate, or carbonate
- possium nitrate, KNO3, and potassium chlorate, KClO3, are used in fireworks
- potassium bromide, KBr, was used as an antaphrodisiac - oh dear!
- potassium permanganate, KMnO4, is an important oxidizing agent
- low-sodium salt
- potassium hydroxide is used in the preparation of potassium phosphates for liquid detergents