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.
7. It is available in pure form.