The New InternationalTemperature Scale of 1990 (ITS-90)

Temperatures on the ITS-90 will agree more closely with thermodynamic temperatures; therefore, the ITS-90 repre-sents a substantial improvement over the IPTS-68(75). For-tunately for the clinical laboratory community, the change in the scale will be at most only 0.05 #{176}Cor less in the range from 0 to 60 #{176}C,but corrections in primary calibrations should be made so that the calibrations are based on the ITS-gO. In a previous publication (1), the most recent internation-ally adopted temperature scale, the International Practical Temperature Scale of 1968 (amended edition of 1975), designated IPTS-68(75), was discussed in some detail and a brief description was given of its evolution. A new tempera-ture scale will be implemented on 1 January 1990, the same date that changes in some electrical quantities will be made (2-6). The new scale (7),the International Temperature Scale of 1990 (1TS-90), will supersede the IPTS-68(75) and also a provisional low-temperature scale, the Echelle Provi-soire de Temperature de 1976 entre 0.5 K and 30 K (EPT