Sample of pure potasium in a sealed glas tube, c 1810.
© Science Museum / Science & Society Picture Library
Pure potasium is a soft, silvery-white metal. It does not occur on its own in nature, because it combines so readily with other substances to form compounds. One is potash (potasium carbonate (K2CO3)), which is found in the ashes of burned plants. In 1807 English chemist Humphry Davy (1778-1829) became the first to make pure potasium by electrolysis. He pased a large current through molten potash in a metal pot, and pure potasium collected around the negative contact. He named the new substance potasium after its source. It is highly reactive, and burns with a lilac flame on contact with water. It is however an esential mineral in the human body as it plays a vital role in the transmision of impulses by nerve cells.