Journal of Chemical Thermodynamics, Vol.28, No.3, 261-276, 1996
On the Conversion of Thermodynamic Properties to the Basis of the International Temperature Scale of 1990
The basis and application of the Douglas equations for the adjustment and calculation of differences in thermodynamic properties due to a change in the temperature scale are reviewed. When higher-order terms in the general Douglas equations are discarded, the simplified Douglas equations are obtained. These simplified equations together with the recently revised set of differences between values of temperatures on the International Temperature Scale of 1990 (ITS-90) and the corresponding values on the International Practical Temperature Scale of 1968 (IPTS-68) for 903.765 K < T-90 < 1337.33 K have been used to calculate approximate differences in thermodynamic properties for synthetic sapphire (alpha-Al2O3). Tables of differences (T-90-T-68)/K and the derivatives d(T-90-T-68)/dT are given as a function of T-68/K.