A thermodynamic inspection of the new Provisional Low Temperature Scale from to , PLTS-2000

The melting curve of 3 He is used as the new extension of the International Temperature Scale of 1990, the PLTS-2000. A thermodynamic inspection of this scale is described. It has been carried out by application of the Clausius–Clapeyron equation to the available thermal and pVT data of the liquid and solid phases. The overall agreement is found to be very good. The remaining small discrepancies are within experimental error. Nevertheless, the present thermodynamic inspection does not allow a further narrowing of the uncertainty margin at the lowest temperatures of the new scale.