At the beginning of the 19th century, after Volta A.G. 1745-1827 (Italy) invented the battery, chemists all over the world succeeded in using the battery to decompose water.
Davy H. 1778-1829, a British chemist, persistently engaged in the experimental research of using batteries to decompose various substances. He hoped to use batteries to decompose caustic potash into oxygen and an unknown "base", because chemists at that time thought that caustic soda was also an oxide.
It was first tested with saturated solution of caustic potash, but the results obtained were the same as that of electrolytic water, only hydrogen and oxygen were obtained.
Later, he changed his experimental method, electrolyzing molten caustic potash, and small beads with metallic luster similar to mercury appeared on the cathode. Some of the beads immediately burned and exploded, forming a bright flame, while others did not burn, but the surface became dark and covered with a white film. He threw this small metal particle into the water, which made a flame and made a piercing sound.
In this way, David discovered metallic potassium on October 6, 1807, and a few days later, he obtained metallic sodium from electrolytic caustic soda.