Ask a Teacher

Mercury does not fall or rise in a clinical thermometer when taken out from the mouth because of the special arrangement known as KINK present in it.

 For a medical thermometer to get a reading of the patient's temperature even after it has been removed from the patient, we need to stop the mercury shrinking back into the reservoir. The kink does this, it breaks the connection between the mercury in the capillary and the reservoir so the reading given is accurate.