A THERMODYNAMIC CALCULATION OF THE VAPOR-PRESSURE VS TEMPERATURE RELATION OF HE-3

Vapour pressures of He-3 have been calculated from experimental data o n the virial coefficients of the vapour phase and heat capacities and densities of the liquid phase, together with a chosen value for the he at of vaporization at T = 0. The results of the calculations are compa red with the vapour pressure equations for He-3 which define internati onal temperature scales (EPT-76 and ITS-90). Between 1 K and 0.5 K dif ferences from the latter scales have been found, amounting to + 1 mK a t 0.5 K, similar to results obtained from magnetic thermometry and the rmodynamic calculations by other authors.