SIMPLE APPARATUS FOR DEMONSTRATING BOYLE'S LAW EDWIN E. HAYS
AND
R. G. GUSTAVSON*
University of Denver, Denver, Colorado
EFFECTIVE teaching depends on recognizing the ments of the plunger from a distance. Students cerfact that all think in^ is an ormnization of ex~erience. tainly are impressed as they watch the barometer readThe primary purpose of lecture demonstrations and laboratory work is to supply the experience on which thinking is to be based. The apparatus described in this article was developed for students taking college -0
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TO VACUUU O R PRESSURE
2
3
4
5 6 7 Volume in cc. FIGURE1
8
9
1
0
chemistry without any previous chemical instruction. The apparatus consists of a syringe of 10 cc. capacity placed in a large test-tube, which in turn is connected with a mercury barometer. (A 10-cc. syringe with a broken plunger may frequently be obtained from friends among physicians or veterinarians.) The system is provided with connections to a water asvirator. A convenient volume is sealed off by placing the bottom of the syringe in a rnbber stopper. A small light is placed in back of the tube containing the syringe to aid in reading the instrument. It is only necessary that the bottom of the plunger be intact. The inside of the plunger may be colored with black paint to aid in taking readings and to enable students to follow the move-
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'Present address: University of Colorado, Boulder, CoIorado.
I
I
FRONT
SCALE: 3/16'' CPUALS I"
WITH SIDE OF BOX REMOVED
F~OURE 2
ingsdecrease to halfvalues and the volumes in the syringe double themselves. This is especially true when the barometer readings are low, when a small decrease in pressure brings about a very large increase in volume. Readings may be taken and plotted on the blackboard to give a typical Boyle's law curve. The instrument is not a precision instrument, but it does help the student visualize the pressure volume relationships.
