Apparatus for electrolysis, 1800-1820.

UNITED KINGDOM - JUNE 26: The item on the left is a reproduction of the voltaic pile used by Anthony Carlisle (1768-1840) and William Nicholson (1753-1815) to electrolyse water in 1800. The electrolysis cell in the centre dates from about 1810 and is very similar to the apparatus used by Humphry Davy (1778-1829) in 1807 to prepare potassium by the electrolysis of potash (potassium hydroxide). The apparatus on the right dates from around 1820 and is similar to that used by Davy to demonstrate the electrolysis of water at the Royal Institution. The experiment showed that hydrogen and oxygen were produced in the decomposition of water. (Photo by SSPL/Getty Images)