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
Mercury-in-glass thermometer period of time, typically 24 hours. The original design contains mercury, but solely as a way to indicate the position of a column of alcohol whose expansion indicates the temperature; it is not a thermometer operated by the expansion of mercury; mercury-free versions are available. Mercury thermometers cover a wide temperature range from ; the instrument's upper temperature range may be extended though the introduction of an inert gas such as nitrogen. This introduction of an inert gas increases the pressure on the liquid mercury and therefore its boiling point is increased, this in combination with replacing the Pyrex glass