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About CCA!
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| The demonstration on this page requires the use of a large volume of mercury. It is not intended to represent an exercise for chemistry laboratory students. Do not attempt to duplicate this demonstration without taking appropriate safety precautions. |
Narrative
A safer way to fill a barometer is to use a vacuum pump to
create a vacuum at the top of the barometer. This draws the
mercury up into the tube from the dish at the bottom. Continuing
to draw a vacuum does not change the level of the mercury inside
the tube. Again, the pressure is 731 millimeters of mercury.
Closing the valve maintains the vacuum when the hose is
removed.
Standard atmospheric pressure is 760 millimeters of mercury but
barometer readings vary with weather conditions and are lower at
higher elevation.
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