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The evolution of ITS-27 and its modifications in 1948
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Summary
The normal hydrogen scale
The International Temperature Scale of 1927
The evolution of ITS-27 and its modifications in 1948
The 1958 4He and 1962 3He vapour pressure scales
The International Practical Temperature Scale of 1968 (IPTS-68)
The 1976 Provisional 0.5 K to 30 K Temperature Scale (EPT-76)
The International Temperature Scale of 1990 (ITS-90)
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  1937
The CIPM established a Consultative Committee on Thermometry and Calorimetry to advise it on matters concerned with these subjects. Since then, it has been the Consultative Committee on Thermometry (CCT) that has largely taken the initiative in matters concerned with the evolution of the International Temperature Scale.

  1948
The first revision of the ITS took place in 1948. In this revision, the only change below 0 °C was the disappearance of the extrapolation below the oxygen point, to –190 °C, which had been found to be unreliable. The IPTS-48 extended down only to –182.97 °C. The junction between the resistance thermometer and the thermocouple was changed from 660 °C to the freezing point of antimony, 630.5 °C, and the temperature assigned to the silver point was increased slightly, from 960.5 °C to 960.8 °C. It was also decided to drop the name "degree Centigrade" for the unit and replace it by degree Celsius.