The Decomposing Vessel is used to electrolyze water to produce hydrogen and oxygen gas. In the Colby apparatus test tubes are inverted over the platinum electrodes to collect the gas; the test tubes are originally filled completely with water. The Harvard apparatus has the electrodes sealed into the U-tube, and only the base of the Allegheny instrument remains.     Once the two gases have been collected, they may be exploded in Volta's Pistol. The hydrogen can be exploded after being mixed with air, and the oxygen can be used to make a flame burn brighter.     The glass tubes of the St. Mary's apparatus are graduated to show the two to one volume ratio of hydrogen to oxygen.

                  St. Mary's College                                Harvard University                                    Allegheny College

The Decomposing and Recomposing Water Apparatus at the left is described in the 1881 catalogue of E.S. Ritchie & Sons of Boston as "A strong glass receiver, capped each end, with sliding-rods and platinum electrodes; mahogany base and pillar, with graduated jar to measure the gas evolved by the displacement of water. To recompose, turn the electrodes into the gas, and pass the electric spark, ...$10.00"    The graduated jar was a tall measuring cylinder that stood on the side of the base; a tube led downward from the left-hand brass fitting to the bottom of the jar that was partly filled with water to contain the gas.    The apparatus is in the Millington/Barnard Collection at the University of Mississippi in Oxford.