Establishment of a practical temperature scale in the range of 10–90° K

Summary

• 1. In establishing a temperature scale in the range of 10–90° K, four platinum thermometers (α ≂ ≂ 0.003925) were compared at 107 different temperatures with a gas thermometer which had no dead space. Comparisons were made in an adiabatic cryostat in the range of 10.7 to 94.9° K [27].

• 2. From the worked-up experimental data, smoothed calibration tables for W_ux6 (T) and T(W_ux6) were compiled, showing the relation of the mean relative resistance of all the group thermometers to temperature.

• 3. The group of four ux6 thermometers determines the practical temperature scale in the range of 10° to 90.19° K. This group serves as the primary practical standard for the scale in this range.

• 4. The practical scale is related to the recognized scale, which operates above the oxygen point, by means of the numerical value of this point$T_{O_2 } = 90.19^\circ K$. If this value of the oxygen point temperature is changed, all the temperatures of the practical scale should be multiplied by the ratio$\frac{{T_{O_2 } }}{{90.19}}$, where$T_{O_2 }$ is the new oxygen point temperature.

• 5. The practical scale is an approximation to the thermodynamic scale of temperatures. These two scales differ by the following amount:

  $$T_{ther} - T_{pract} = T_{pract} \left[ {\frac{{T_{O_2 } }}{{90.19}} - 1} \right] \pm \eta + \delta .$$

• 6. Further tests of the thermometers showed that the reproducibility of their readings, established by mutual comparisons, is better than ± 0.002°. The variations of the thermometer readings is in any case smaller than the errors in producing reference points.