Mercury-in-glass thermometer ushered in a new era of accuracy and precision in thermometry, and is still to this day regarded as one of the most accurate thermometers available. The thermometer was used by the originators of the Fahrenheit and Celsius scales. Anders Celsius, a Swedish scientist, devised the Celsius scale, which was described in his publication "The origin of the Celsius temperature scale" in 1742. Celsius used two fixed points in his scale: the temperature of melting ice and the temperature of boiling water. This wasn't a new idea, since Isaac Newton was already working on something similar. The distinction of Celsius
International Temperature Scale of 1990 rising again to 10 mK at temperatures close to 430 K, and reaching 46 mK at temperatures close to 1150 K. The table below lists the defining fixed points of ITS–90. International Temperature Scale of 1990 The International Temperature Scale of 1990 (ITS–90) published by the Consultative Committee for Thermometry (CCT) of the International Committee for Weights and Measures (CIPM) is an equipment calibration standard for making measurements on the Kelvin and Celsius temperature scales. ITS–90 is an approximation of the thermodynamic temperature scale that facilitates the comparability and compatibility of temperature measurements internationally. It specifies fourteen calibration points ranging