Humphry Davy. Coloured historical engraving of the English chemist Sir Humphry Davy (1778-1829). In 1807, Davy isolated potassium and sodium by driving an electric current into solutions containing potash and soda respectively. This technique is known as electrolysis. Later Davy obtained other metals such as barium, strontium, calcium and magnesium using similar methods. In 1815 he invented a miners' safety lamp known as the Davy lamp. This special lamp could be safely used in gassy coal mines. Early on in his career he discovered nitrous oxide (laughing gas), the first chemical anaesthetic used. Engraving from a portrait by T. Lawrence.