Potassium is an element with symbol K (derived from Latin kalium) and atomic number 19. It was first isolated by Sir Humphry Davy in 1807. The term “potash” refers to potassium extracted from wood ash, and it was used in early times to make soap. qali for alkali. Potash is one of the potassium compounds known to man since ancient times.
Pure potassium is a lightweight silvery metal that is soft enough to cut with a knife.
Potassium compounds emit a lilac or violet flame color when burned.
The potassium ion is important for all living cells. Animals use sodium ions and potassium ions to generate electric potentials. This is vital for many cellular processes and is the basis for the conduction of nerve impulses.
The recommended daily allowance (RDA) for potassium is 4,700 mg. Potassium is abundant in a variety of foods — in particular unprocessed fruits and vegetables. Thus, it’s quite simple to meet the daily requirement. A baked potato, for instance, contains a whopping 900 mg of potassium.
Most of the universe’s potassium atoms were made in the final moments of giant stars as they exploded in supernovae. Potassium is made in the oxygen burning shell of stars when they explode. This is not normal burning, of course; it is nuclear fusion. Potassium is made, along with several other elements including sulfur, and silicon, during explosive oxygen burning in supernovae.
The radioactive isotope potassium-40 gives us a way of dating rocks. Potassium-40 decays to argon-40 and calcium-40 with a half-life of 1.25 billion years. The ratio of potassium-40 to argon-40 trapped in rock is used to determine how long it is since the rock has solidified.
All plants need potassium to survive; over 90% of all human use of potassium compounds is in the manufacture of plant fertilizers.