Refrigeration -4 Demonstration for the Classroon~ EARL F. SHUMAKER Kent Stote Training School, K-t, Ohio
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T HAS been found that it is quite difficult for the average science student to understand refrigeration, and especially the flame-type refrigerator. As a direct outgrowth of that difficulty the following simple apparatus was devised to demonstrate both refrigeration and the way in which a flame can be used to make something cold. An ordinary soft-glass test tube was heated near the center and drawn out so that the bottom of the test tube formed a bulb on one end. A concentrated solution of ammonium hydroxide was then put in the bulb. The open end of the tube was then heated and drawn to a small opening, which was easily sealed, thus giving bulbs a t each end. The end of the unit containing ammonium hydroxide was gently heated, which drove off gaseous ammonia, which in a short time built up enough pressure
Ammonium Hydroxide Solution
Liquid Ammonia
to cause it to liquefy and collect in the cool end. After a small quantity was thus prepared the apparatus was passed around the class, so that they could see the liquid ammonia boil, due to its taking heat from its surroundings, and feel the wide difference in temperature between the two ends.
