Daniel Gabriel Fahrenheit Hague and was buried there at the Kloosterkerk (Cloister Church). According to Fahrenheit's 1724 article, he determined his scale by reference to three fixed points of temperature. The lowest temperature was achieved by preparing a frigorific mixture of ice, water, and ammonium chloride (a salt), and waiting for it to reach equilibrium. The thermometer then was placed into the mixture and the liquid in the thermometer allowed to descend to its lowest point. The thermometer's reading there was taken as 0 °F. The second reference point was selected as the reading of the thermometer when it was placed in still
Medical thermometer is placed properly. Allbutt, T.C., “Medical Thermometry”, "British and Foreign Medico-Chirurgical Review", Vol.45, No.90, (April 1870), pp.429-441; Vo.46, No.91, (July 1870), pp.144-156. Medical thermometer A medical thermometer (also called clinical thermometer) is used for measuring human or animal body temperature. The tip of the thermometer is inserted into the mouth under the tongue ("oral" or "sub-lingual temperature"), under the armpit ("axillary temperature"), or into the rectum via the anus ("rectal temperature"). The medical thermometer began as an instrument more appropriately called a water thermoscope, constructed by Galileo Galilei circa 1592–1593. It lacked an accurate scale with which to measure temperature