Also known as "Jacob's Ladder", the arrangement of a pair of horn electrodes attached to a high voltage, high frequency AC supply has been a classroom favorite for many years. When power is applied, a stationary arc forms at the narrowest point between the electrodes. As the discharge heats the ionized air it rises, carrying the discharge upwards until it is extinguished near the top, to be replaced by a new discharge at the narrowest point. In this newly developed model, the power supply is built into the base, and delivers approximately 12kV at 25kHz. All electrical parts are totally enclosed for safety. The clear tube enclosing the electrodes has a cap with a hole and a stopper with a bent glass tube. After operation of the apparatus for several minutes, oxides of nitrogen formed in the discharge collect in the tube and can be aspirated for chemical testing.

This dramatically illustrates the "fixation" of atmospheric nitrogen by lightning discharges. With power cord for 110VAC outlet, and instructions.