A mercury barometer consists of a tall glass tube filled with mercury inverted into a container of mercury. The mercury in the tube will fall until the weight of the mercury column is balanced by the atmospheric pressure pushing down on the surface of the mercury in the container. The measurement is then taken from the height of the mercury column in the tube.
A water barometer would have to be many feet tall because the density of water is much lower than that of mercury. In addition, the vacuum above the column would be spoiled by the water vapor pressure, far higher than that of mercury, and strongly temperature dependent.
In the mercury barometer, atmospheric pressure balances a column of mercury, the height of which can be precisely measured. Other liquids can be used in barometers, but mercury is the most common because of its great density.Mainly due to its high density
Because it has a high density... meaning that the volume increase or decrease due to altitude change is can be viewed in a practical sized barometer. If water, which had a much lower density, was used instead of mercury, the barometer must be at least 15m high.
The common method to measure atmospheric pressure employs an inverted column submerged in a fluid to determine the level at which the column has to be raised to equalize the external atmospheric pressure and the internal column pressure. The height at which the fluid inside the column ceases to increase is correlated to atmospheric pressure. Due to mercury's high density, this level is on the order of inches (~30 inches of mercury at atmospheric pressure). If water were to be used the column would have to be ~32 feet tall in order to develop the equalized pressures between the column and atmosphere.
In most laboratories, with great difficulty. Mercury is a highly toxic substance and its use is very strictly controlled.A mercury barometer is simple because the height of the mercury column would be 760 mm (approx 30 inches). Mercury has a density which is around 13.6 times that of water. The next most dense fluid which is readily available (and safe) has a density which is about a tenth as much. For this, you would require a column which was about 7.6 metres (25 feet) tall! That is not a simple piece of equipment.
Purely a matter of convenience. A water barometer is entirely feasible, but the column height at normal atmospheric pressure is over 32 feet tall. In order to make the barometer more compact, it's convenient to use the heaviest available liquid. Mercury has a little more than 13 times the density of water, so the column height in a mercury barometer is only about 30 inches tall, making for a much more manageable instrument.
Following are the reasons why mercury and not water is used in a barometer:1. Mercury is relatively denser than water, consequently the length of the column of water would have to be about 34 feethigh to exert pressure equal to that of the atmosphere while the column of mercury need to be only 30 inches to exert pressure equal to that of the atmosphere.2. Mercury has a very low vapor pressure when compared to that of water. So it is more sensitive than water to the changes in the atmospheric pressure and rises more quickly to record the changes in the atmospheric pressure.3. Mercury's freezing point is much lower than that of water's so it can record the atmospheric pressure at temperatures below that of 0 degrees centigrade.4. Mercury does not evaporate easily so very little mercury vapor enters the vacuum above the mercury in the tube.5. Mercury being a metal shines brightly and so can be used to read the markings on the tube easily.
Nelson's Column is 169 feet tall.
It will be difficult as the hose is opaque making reading it visually impossible.You will need roughly 30 feet of hose suspended vertically above the bucket with the top end sealed shut and filled with water.
Jason Mercury is 6'.
Mercury Morris is 5' 10".