Explanation

Mercury is used as a thermometric fluid because it has several ideal properties:

1. High Boiling Point (B.P)

   • Mercury doesn't evaporate easily, which makes it suitable for measuring high temperatures.

2. Low Freezing Point (not high M.P)

   • Mercury has a low melting point (−38.83°C), which helps in measuring low temperatures, though this limits it in very cold environments.

3. Stable and Uniform Coefficient of Expansion

   • Mercury expands uniformly with temperature, which gives accurate and consistent readings.

4. Visibility and Non-wettability

   • Mercury is shiny and opaque, so it's easy to see in a glass tube.

   • It doesn't stick to glass, which keeps the readings clean and precise.