All of you might have seen doctors using clinical thermometers to take your body temperature since childhood. However, after looking at that black line in the glass structure, letting you know about the fever is fascinating enough. Subsequently, as you have grown up, are aware of the mercury, the black line rising in thermometers, but have you ever wondered, why only mercury is used out of all other elements? How does it work inside it?
So here you can find answers to such questions with us in this blog.
Why using mercury over other elements?
There exist an enormous number of metals that are good conductors of heat but are solid at room temperature whereas mercury is a good conductor of heat and the only element that remains in a liquid state at room temperature. Due to this reason, mercury doesn’t fracture the glass tube of the thermometer. Further, it is capable of indicating the temperature rapidly with perfection due to its high coefficient of expansion.
Advantages of Mercury.
- Its high boiling point makes it very suitable to measure higher temperatures.
- Being a good conductor of heat its rising level indicates the temperature as quickly as thinkable with higher accuracy.
- It is opaque and bright, making its movement easily visible inside the capillary.
- As it doesn’t stick to the glass walls of the thermometer is capable of moving easily inside the capillary glass tube.
- It tends to provide the correct temperature, as its expansion is constant alongside the whole range of heat.
- The expansion of mercury is relatively large even for a small temperature change, thereby making it useful to mark letterings on the thermometer surface.
- Due to its property of being less volatile, a small quantity of mercury vapor that remains above the liquid mercury in the thermometer does not obstruct the measure of mercury.
- Having a freezing point of – 39℃ and the boiling point is 357℃, mercury remains in the liquid form for a long time.
- It doesn’t vaporize easily even at very low temperatures.
How does it work inside the thermometer?
Mercury has a high coefficient of expansion at a given temperature. It is due to this reason, on receiving an appropriate amount of temperature it starts rising being in its liquid form. Once it reaches a state of temperature that remains constant, its expanding tendency halts down. The risen level of the liquid mercury in the capillary glass tube thus provides you the actual reading on clinical temperature.
