LECTURE-DEMONSTRATION OZONIZER GUY M. LISK, NORTHWESTERN STATE TEACHERS' COLLEGE, ALVA. OKLAHOMA
This article describes a simplified form of apparatus to be used as an ozone generator, and which may also be used to illustrate the diffusion of gases. The accompanying diagram is labeled as follows: K-Large-mouthed bottle. (A pint Mason fruit jar serves admirably.) B,B-Spark gap posts not quite touching C,C. D-Removable glass plate as large as size of K will permit. C,C-Removable metal plates somewhat smaller than D. A,A-Thin copper strips connecting B,B to binding posts. To operate the ozonizer remove jar, glass plate, and metal plates. Attach induction coil to binding posts, and allow a spark to jump across gap. Now insert metal plates, and allow spark to jump from plate to plate. Next, insert glass plate, and while no sparks are seen to pass from plate to plate, that the current is really unbroken is shown by the sparks which can still be seen passing from the posts to the metal plates. It is hoped that this will enable the student to "see" that the electric charge is still passing through the glass OWNIZER LECTURE-DEMONSTRATION plate and the intervening gas, and thus be able to appreciate the results obtained in the final demonstration. The glass jar is now placed in position (with mouth up if desired), and the current turned on for a short period; the jar will now be found to contain ozone as can be proved by the odor and the usual starch-iodide test. From a pedagogical standpoint it would probably be best to use a jar of pure oxygen first, and then use air, thus avoiding the possibility of the question arising as to whether or not the results obtained were not due to a combination of oxygen and nitrogen. To use this apparatus to illustrate diffusion of gases, remove the glass and metal plates. Place a small strip of wood near each spark gap post to serve as a support for the glass jar, thus leaving a space between the jar and the block. Fi jar with hydrogen, and place in position, mouth downward, resting on the strips of wood. When the spark is first passed nothing occurs, 2429
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DECEMBER, 1931
but by the time your "bright" student has explained why the hydrogen does not ignite, a second spark will cause the to-be-expected explosion. More explanations are now in order as to how the light gas went down, and the heavy gas up. It is well to see that the mouth of the jar is dry before placing i t in position, thus avoiding the chance of a "short" a t the mouth of jar which would spoil the demonstration. A blotter pressed for a moment against the jar takes care of this difficulty. Of course, if tank hydrogen is used this precaution is unnecessary.
