Question

Water is not used as a barometric liquid because

• A. it is difficult to have a barometer tube 11 m long.
• B. water vaporises under vacuum conditions.
• C. water sticks to the side of glass tube.
• D. all the above

Answer 1

Answer: (D)

all the above

Mercury is more dense. Its relative density is $13.534$ times that of water. So, to measure the atmospheric pressure, which is $760mm$ of mercury you need a barometer ,with mercury, of length slightly more than $0.76m$, say one meter to cover the special cases of some higher pressure. If you use water, you have to have the length of barometer of length (or height) $13.534$ times the length of mercury barometer, which may be more than $11m$ in length.

Further mercury, being a metal has the shining quality which highlight its reading clear. Also mercury, having comparatively lower specific heat and good conductor of heat, could come to the same temperature of the atmosphere more quickly.