Gas Thermometer Determinations of the Thermodynamic Temperature Scale in the Range -183 °C to 100 °C

The thermodynamic temperature scale was realized over the range -183 °C to 100 °C by using a helium constant volume gas thermometer. The scale was compared with the International Practical Temperature Scale using platinum resistance thermometers. The IPTS appears to differ from the thermodynamic scale by about -10 millidegrees at the oxygen point and +0.5 millidegree at the steam point. Differences at intermediate temperatures are considerably higher (up to 36 millidegrees). The estimated accuracy of these results is ±2 millidegrees.