Why is only mercury used in clinical thermometer ?
A clinical thermometer is used to measure human body temperature. It consists of a long glass tube which is graduated. A thermometric liquid is present within the tube which expands proportionally to temperature,hence measures it.
Mercury is best suited as a thermometric liquid:
1. It expands uniformly when heated.
2. It has low specific heat capacity.
3. I has a high boiling point (357 °C) and a low freezing point (-39 °C).
4. It is a good conductor of heat.
5. It does not stick to the walls of the glass tube.
6. It is opaque and shiny and hence clearly visible.