In a vacuum, the absence of air pressure prevents liquids like mercury from boiling in a barometer, making it a suitable option due to its high density and boiling point.
Boiling in a vacuum: In a vacuum tube of a barometer, the liquid doesn't boil because boiling occurs when the vapor pressure of the liquid equals the atmospheric pressure. In a vacuum, the absence of air pressure prevents the liquid from reaching its boiling point. For example, liquid mercury in a barometer remains a liquid in a vacuum due to the low pressure.
Mercury barometer: Mercury is commonly used in barometers because of its high density, which results in a shorter column height compared to water. Additionally, mercury's high boiling point makes it suitable for barometric measurements as it doesn't evaporate easily in the barometer tube.
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