2006-06-23 07:16:38 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Other - Science
Because it doesn't freeze under normal weather conditions but still reacts to atmospheric changes.
"Barometers are instruments that measure air pressure. The mercury barometer was developed in the 17th century. They are still used today, but many of today's barometers use aneroids to detect air pressure. (Related: How a mercury barometer works).
To make a record of the air pressure and how it's changing, and aneroid is connected connected with a device that records air pressure, making it an aneroid barograph.
An aneroid is a flexible metal bellow that has been tightly sealed after having some air removed. Higher atmospheric pressures squeeze the metal bellows while lower pressures allow it to expand.
The aneroid barograph consists of a slowly rotating cylinder with paper on it that can give up to a week's worth of air pressure records before new paper is needed.
As you can see in the graphic above, a pen at the end of a lever attached to the aneroid moves up and down according to pressure changes and records the pressure on the paper wrapped around the cylinder.
The aneroid barometer has some advantages over a mercury barometer because it is much smaller and can also record a week's worth of data. The aneroid barometer is the heart of altimeters used in modern aviation." http://www.usatoday.com/weather/waneroid.htm
2006-06-23 07:20:30 · answer #1 · answered by philk_ca 5 · 1⤊ 1⤋
For a barometer to work the top part of the tube is under vacuum(zero pressure) water would boil until the pressure matches the vapor pressure of the water. Hence the pressure above the liquid is high. For mercury the pressure is about 10-5 Torr or about 1/100,000,000 of an atmosphere.
Alcohol would be even worse to use.
2006-06-23 10:25:38 · answer #2 · answered by metaraison 4 · 0⤊ 0⤋
Short answer - because of its density. A water barometer would have to be greater than 30' tall vs 30" with mercury.
2006-06-23 07:36:00 · answer #3 · answered by williegod 6 · 0⤊ 0⤋
Mercury expands significantly with change in temperature/pressure. Water does not.
2006-06-23 07:20:24 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Mercury is probably used instead of water because of its weight and color. but to be sure look it up : )
2006-06-23 07:23:28 · answer #5 · answered by *butterfly* 2 · 0⤊ 0⤋
because mercury has a higher boiling point than water
alcohol is also used for the same reason
2006-06-23 07:20:17 · answer #6 · answered by smartmitch 4 · 0⤊ 0⤋
If water is used, a very long tube will be required.
2006-06-23 07:20:43 · answer #7 · answered by ag_iitkgp 7 · 0⤊ 0⤋
13.6 times more dense. If water was used, the column (about a meter) would be 13.6 times taller....not very convenient.
2006-06-23 07:20:47 · answer #8 · answered by Anonymous · 0⤊ 0⤋
and because the water would freeze when too cold.
2006-06-23 07:21:21 · answer #9 · answered by Tom B 4 · 0⤊ 0⤋