To prepare and collect several jars of oxygen.
Fill gas jars to the brim with water and cover with well-vaselined gas jar covers. Invert them, in turn, over water contained in a glass trough and remove the covers beneath the water surface. Take care that no air bubbles enter the gas jars. Set up the apparatus as shown in the diagram. The glass test tube contains oxygen mixture and carries a delivery tube; pass the tube under the beehive shelf. Now heat the mixture. When the bubbling of gas becomes quite free and vigorous, place the gas jars in turn on the beehive. Collect some jars of the gas, cover them up with the covers again beneath the water, and-remove them from the trough. Do not stop heating until after the end of the delivery tube has been removed from the water.