Clinical Mercury Thermometer

In a mercury thermometer, a glass tube is filled with mercury and a standard temperature scale is marked on the tube. With changes in temperature, the mercury expands and contracts, and the temperature can be read from the scale. Mercury thermometers can be used to determine body temperature.
A clinical thermometer is a thermometer used to measure human body temperature. Most made in the 20th century are mercury-in-glass thermometers. They are accurate and sensitive, having a narrow place where the mercury level rises very fast. A kink in the tube stops the mercury level from falling on its own.
Mercury is used in thermometers because It has a high coefficient of expansion so that even a small rise in temperature brings about sufficient expansion which can be detected in the capillary of the calibrated part of the thermometer.
A basic mercury thermometer is a precisely crafted piece of tube-shaped glass enveloping a mercury-filled reservoir connected to an extremely thin channel, called the capillary bore, that provides a chamber the mercury from the reservoir can expand into.