Potassium is the seventh most common element on Earth, which we mostly know as a material called potash. It always used to be obtained by burning wood. What was left was ash high in potassium – literally pot-ash, the ash left in the pot.

Potassium is a very soft light grey metal. It will flare up in air and is never found as a metal naturally.

Like sodium, potassium is essential to life, and it is found in most foods. The way it works is to be in the body, pulling nourishment out of the blood and into our body cells. It does not give the same problems about high blood pressure as sodium, and people with high blood pressure use potassium as a salt substitute. Its main use, however, is in fertilisers.