Deviation of International Practical Temperatures from Thermodynamic Temperatures in the Temperature Range from 273.16 K to 730 K.

The range over which thermodynamic temperatures have been realized by gas thermometry at the NBS has been extended to 730 K. The results are preserved by measuring the corresponding international practical temperatures. The difference between them is expressed as the following polynomial: $T/K-T_{68}/K_{68}=-120,887.784/T_{68}^2+1213.53295/T_{68}-4.3159552+6.44075647\times {10}^{-3}{T}_{68}-3.56638846\times {10}^{-6}{T}_{68}^2$ which is valid in the range 273 to 730 K. The difference found and the estimated uncertainties at the three defining fixed points in the range covered are [Table: see text].