Potassium is the chemical element with
the symbol K, atomic number 19, and an atomic mass of
39.098. 
Things you might not know about
Potassium:
- It reacts violently with water, causing
eruptions.
- It makes up about 2.4% of the weight of the
Earth's crust.
- It helps to regulate the level of body
fluids, maintain normal blood pressure, keep the heart functioning
properly and regulate the working of the nervous system by
promoting proper functioning of the tissues.
- Its name comes from the English word
'potash', which means an alkali extracted from the ash of burnt
wood or tree leaves.
See GC2XAY2 - Hydrogen, for an explanation
about this series of caches.