APRIL, 1950
HYDROGEN DEMONSTRATION CANNON MADE OF GLASS J. E. RANSFORD, S.J. Fordham University, New York, New York A SECTION of pyrex tubing 1'/2 in. or 2 in. in diameter about 12 in. long should be wrapped lengthwise and crosswise about every inch or so with 3/4-in. Scotch tape. Close one end of the tube with a solid rubber stopper through which copper electrodes (heavy copper wire, insulated outside of stopper) have been forced about two inches. The tips of the electrodes should be adjusted so that they are about '/a in. apart. The ends outside the stopper (terminals) should be long enough to make snitable connections with a high frequency source. Clamp this end of the tube vertically and solidly against the base of a heavy ringstand. Fit the top end (mouth of the cannon) with a suitable cork stopper which is well coated with petroleum jelly or stopcock grease. A festoon of colored paper strips or ribbons may be fastened to the outside surface of the cork-the better to follow the cork in flight. With the cork removed, run hydrogen for about 30 seconds from a generator (e. g., Kipp) down the mouth of the cannon through a glass tube that will reach t o the bottom. Oxygen need not he added-for the air in the tube will usually be su5cient to form an explosive mixture with the hydrogen thus added. Shut off t h e generator. Remove the nozzle. Stopper the mouth of the cannon quickly and firmly, but W t tightly. Then, place the generator a t a safe distance from the cannon and also from the high-frequency source. Connections from a high-frequency source (e. g., a Model-T Ford spark coil) should be ready to be fastened to the electrode terminals. It is advisable tousea switch on an extension cord, and to stand a t a safe distance from the cannon before closing the circuit. Be
SCOTCH TAPE
Glass Hs Cannon
prepared for a loud report when the cannon is firedand make sure that the festooned cork bas a free path t o the ceiling. This demonstration gives striking proof of the dangerous as well as the powerful explosive force of an ignited mixture of hydrogen and air. Students usually inquire why it is that the cork is blown out of the cannon, instead of being drawn into it. It is highly advisable to disconnect the high-fiequency source, and examine the pyrex tube carefully for cracks, before reloading and firing the cannon again.
