Reasons for using mercury as a thermometric liquid are :
(a) Mercury has uniform contraction and expansion
(b) Mercury does not stick to the sides of the capillary tube
Thus it helps in recording accurate temperature
(c) Mercury is opaque and shining Thus it can be easily seen as a fine thread in the capillary tube
(d) It has high boiling point 257∘C and low freezing point (−39∘C) so it can be used to measured and only wide range of temperatures