The NHS was based on verre dur (hard glass) mercury thermometers that had been compared to the normal-hydrogen gas thermometer between 0 [degrees]C and 100 [degrees]C.
27 K (determined either by using a gas thermometer or the specified temperature-vapor pressure relationship of equilibrium-hydrogen--See Table 1), at which capsule standard platinum resistance thermometers (CSPRTs) are calibrated and used for interpolation between the points.
3] for the interpolating constant-volume gas thermometer (ICVGT).
Significant experimental contributions by NBS began with the work of Hoge and Brickwedde (29), who calibrated an ensemble of resistance thermometers against a gas thermometer to establish a scale (known as the NBS-39 Scale) for the calibration of thermometers from 14K to 83K.
T < 120 K) has been maintained at NBS/NIST since 1939 starting with the National Bureau of Standards Constant-Volume Gas Thermometer Scale of 1939 (NBS-39 Scale) (29).