TREVOR CLIFFORD PHOTOGRAPHY / SCIENCE PHOTO LIBRARY TREVOR CLIFFORD PHOTOGRAPHY / SCIENCE PHOTO LIBRARY
Hofmann voltameter in use. The Hoffman voltameter is an apparatus designed by German chemist August von Hoffman in 1866 to demonstrate electrolysis of water. Three glass tubes are connected by a bridge near their bases. The middle tube is used to fill the apparatus with water and a small amount of electrolyte (e.g. dilute sulphuric acid). Each of the other tubes has a platinum electrode sealed into its base and is stoppered at the top. When a current is applied to the electrodes, hydrogen is liberated at the cathode and oxygen at the anode in the volume ratio of 2:1. If both gases are diatomic (which they are), this shows that water contains twice as many hydrogen atoms as oxygen - H2O.
Model release not required. Property release not required.