Celsius degrees disappeared a long time ago, in 1948, as a unit of measurement to replace it Celsius, which is, along with the kelvin, the unit of temperature measurement in the International System of Units, in force in Spain. Review what it contains It happened in the past centuries in units of measure temperature It explains why we often hear or read degrees Celsius despite the fact that they are wrong.
At the end of the nineteenth century, it was International Committee for Weights and Measures Adopted, as a normal thermometer by the International Bureau of Weights and Measures (BIPM), the centigrade scale of a fixed-size hydrogen thermometer, which had as fixed points the melting point temperature of ice (0 °C) and the temperature of distilled water at boiling (100 °C). From that moment on, the unit of temperature will be “Celsius” and will correspond to one hundredth of the difference (at normal pressure) between the melting points of ice and the boiling point of water.
The use of the degree Celsius as a unit of temperature continued until 1948, the Advisory Committee on Thermometry discussed the need to replace the ice point, with the possibility of reproducing an order of a thousand degrees, with the triple point of water. , better defined whose reproducibility was, at that time, in the order of ten thousandths of a degree. The possibility of determining the thermodynamic temperature by a single fixed point was studied, rather than being determined by the interval from 0 to 100. This “revolutionary” idea was finally approved, after many discussions, and the triple point of water became the backbone of the temperature scale, which has been assigned a value of 0.01 °C (or the same, 273.16 K). The triple point is the point at which the three states of matter coexist in equilibrium: liquid, solid, and gas and is defined with respect to temperature and pressure. In the case of water, as I said, 273.16 K and because it is a constant value it helps us calibrate thermometers.
The new definition of the unit of temperature measurement, since November 2018, is based on the exact numerical value of the Boltzmann constant
The General Conference on Weights and Measures in October 1948 approved the single fixed point principle and decided to replace the name “Celsius” with “Celsius” in honor of the Swedish physicist, astronomer, and thermometer expert Anders Celsius who invented the Celsius scale. The percentage is written in the symbol °NS. The search for a new name for the unit of temperature was due to the fact that from the moment the triple point was accepted as a reference and the point system between 0 and 100 was abandoned, the scale ceased to be a degree Celsius and keeping it under that name might cause confusion. That is why since 1948 degrees Celsius does not exist.
employment November 2018 The Twenty-sixth General Conference on Weights and Measures was held and it was also decided to abandon the triple point of water as a reference. Since then, the new definition of the unit of temperature measurement is based on the exact numerical value of the Boltzmann constant, so the term “°C” makes less sense, since the triple point of water is not used in the definition.
Dolores del Campo She is the Director of the Department of Mechanical Quantities and Engineering at the Spanish Center for Measurement and a member of the International Committee for Weights and Measures.
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Formatting and writing: Victoria Toru
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