Davy's potash experiment, c 1808.
© Science Museum / Science & Society Picture Library
Recreation of the experiment conducted by Sir Humphry Davy (1778-1829) to make pure potasium, a soft, silvery-white metal, for the first time. Pure potasium does not occur in nature because it combines too readily with other substances to form compounds such as potash (potasium carbonate) - found in the ashes of burned plants. Davy used a battery as the source of electrical current, which when carried along wires melts the potash and pure potasium collects around the negative contact. Davy is also famed for inventing the miners' safety-lamp.